diff options
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 4959 |
1 files changed, 4959 insertions, 0 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c new file mode 100644 index 00000000000..25049273590 --- /dev/null +++ b/net/ipv4/tcp_input.c @@ -0,0 +1,4959 @@ +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * Implementation of the Transmission Control Protocol(TCP). + * + * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $ + * + * Authors: Ross Biro, <bir7@leland.Stanford.Edu> + * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> + * Mark Evans, <evansmp@uhura.aston.ac.uk> + * Corey Minyard <wf-rch!minyard@relay.EU.net> + * Florian La Roche, <flla@stud.uni-sb.de> + * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> + * Linus Torvalds, <torvalds@cs.helsinki.fi> + * Alan Cox, <gw4pts@gw4pts.ampr.org> + * Matthew Dillon, <dillon@apollo.west.oic.com> + * Arnt Gulbrandsen, <agulbra@nvg.unit.no> + * Jorge Cwik, <jorge@laser.satlink.net> + */ + +/* + * Changes: + * Pedro Roque : Fast Retransmit/Recovery. + * Two receive queues. + * Retransmit queue handled by TCP. + * Better retransmit timer handling. + * New congestion avoidance. + * Header prediction. + * Variable renaming. + * + * Eric : Fast Retransmit. + * Randy Scott : MSS option defines. + * Eric Schenk : Fixes to slow start algorithm. + * Eric Schenk : Yet another double ACK bug. + * Eric Schenk : Delayed ACK bug fixes. + * Eric Schenk : Floyd style fast retrans war avoidance. + * David S. Miller : Don't allow zero congestion window. + * Eric Schenk : Fix retransmitter so that it sends + * next packet on ack of previous packet. + * Andi Kleen : Moved open_request checking here + * and process RSTs for open_requests. + * Andi Kleen : Better prune_queue, and other fixes. + * Andrey Savochkin: Fix RTT measurements in the presnce of + * timestamps. + * Andrey Savochkin: Check sequence numbers correctly when + * removing SACKs due to in sequence incoming + * data segments. + * Andi Kleen: Make sure we never ack data there is not + * enough room for. Also make this condition + * a fatal error if it might still happen. + * Andi Kleen: Add tcp_measure_rcv_mss to make + * connections with MSS<min(MTU,ann. MSS) + * work without delayed acks. + * Andi Kleen: Process packets with PSH set in the + * fast path. + * J Hadi Salim: ECN support + * Andrei Gurtov, + * Pasi Sarolahti, + * Panu Kuhlberg: Experimental audit of TCP (re)transmission + * engine. Lots of bugs are found. + * Pasi Sarolahti: F-RTO for dealing with spurious RTOs + * Angelo Dell'Aera: TCP Westwood+ support + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/sysctl.h> +#include <net/tcp.h> +#include <net/inet_common.h> +#include <linux/ipsec.h> +#include <asm/unaligned.h> + +int sysctl_tcp_timestamps = 1; +int sysctl_tcp_window_scaling = 1; +int sysctl_tcp_sack = 1; +int sysctl_tcp_fack = 1; +int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH; +int sysctl_tcp_ecn; +int sysctl_tcp_dsack = 1; +int sysctl_tcp_app_win = 31; +int sysctl_tcp_adv_win_scale = 2; + +int sysctl_tcp_stdurg; +int sysctl_tcp_rfc1337; +int sysctl_tcp_max_orphans = NR_FILE; +int sysctl_tcp_frto; +int sysctl_tcp_nometrics_save; +int sysctl_tcp_westwood; +int sysctl_tcp_vegas_cong_avoid; + +int sysctl_tcp_moderate_rcvbuf = 1; + +/* Default values of the Vegas variables, in fixed-point representation + * with V_PARAM_SHIFT bits to the right of the binary point. + */ +#define V_PARAM_SHIFT 1 +int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT; +int sysctl_tcp_vegas_beta = 3<<V_PARAM_SHIFT; +int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT; +int sysctl_tcp_bic = 1; +int sysctl_tcp_bic_fast_convergence = 1; +int sysctl_tcp_bic_low_window = 14; +int sysctl_tcp_bic_beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */ + +#define FLAG_DATA 0x01 /* Incoming frame contained data. */ +#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ +#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ +#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ +#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ +#define FLAG_DATA_SACKED 0x20 /* New SACK. */ +#define FLAG_ECE 0x40 /* ECE in this ACK */ +#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ +#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ + +#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) +#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) +#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) +#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) + +#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) +#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) +#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) + +#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) + +/* Adapt the MSS value used to make delayed ack decision to the + * real world. + */ +static inline void tcp_measure_rcv_mss(struct tcp_sock *tp, + struct sk_buff *skb) +{ + unsigned int len, lss; + + lss = tp->ack.last_seg_size; + tp->ack.last_seg_size = 0; + + /* skb->len may jitter because of SACKs, even if peer + * sends good full-sized frames. + */ + len = skb->len; + if (len >= tp->ack.rcv_mss) { + tp->ack.rcv_mss = len; + } else { + /* Otherwise, we make more careful check taking into account, + * that SACKs block is variable. + * + * "len" is invariant segment length, including TCP header. + */ + len += skb->data - skb->h.raw; + if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || + /* If PSH is not set, packet should be + * full sized, provided peer TCP is not badly broken. + * This observation (if it is correct 8)) allows + * to handle super-low mtu links fairly. + */ + (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && + !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) { + /* Subtract also invariant (if peer is RFC compliant), + * tcp header plus fixed timestamp option length. + * Resulting "len" is MSS free of SACK jitter. + */ + len -= tp->tcp_header_len; + tp->ack.last_seg_size = len; + if (len == lss) { + tp->ack.rcv_mss = len; + return; + } + } + tp->ack.pending |= TCP_ACK_PUSHED; + } +} + +static void tcp_incr_quickack(struct tcp_sock *tp) +{ + unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss); + + if (quickacks==0) + quickacks=2; + if (quickacks > tp->ack.quick) + tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS); +} + +void tcp_enter_quickack_mode(struct tcp_sock *tp) +{ + tcp_incr_quickack(tp); + tp->ack.pingpong = 0; + tp->ack.ato = TCP_ATO_MIN; +} + +/* Send ACKs quickly, if "quick" count is not exhausted + * and the session is not interactive. + */ + +static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp) +{ + return (tp->ack.quick && !tp->ack.pingpong); +} + +/* Buffer size and advertised window tuning. + * + * 1. Tuning sk->sk_sndbuf, when connection enters established state. + */ + +static void tcp_fixup_sndbuf(struct sock *sk) +{ + int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + + sizeof(struct sk_buff); + + if (sk->sk_sndbuf < 3 * sndmem) + sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); +} + +/* 2. Tuning advertised window (window_clamp, rcv_ssthresh) + * + * All tcp_full_space() is split to two parts: "network" buffer, allocated + * forward and advertised in receiver window (tp->rcv_wnd) and + * "application buffer", required to isolate scheduling/application + * latencies from network. + * window_clamp is maximal advertised window. It can be less than + * tcp_full_space(), in this case tcp_full_space() - window_clamp + * is reserved for "application" buffer. The less window_clamp is + * the smoother our behaviour from viewpoint of network, but the lower + * throughput and the higher sensitivity of the connection to losses. 8) + * + * rcv_ssthresh is more strict window_clamp used at "slow start" + * phase to predict further behaviour of this connection. + * It is used for two goals: + * - to enforce header prediction at sender, even when application + * requires some significant "application buffer". It is check #1. + * - to prevent pruning of receive queue because of misprediction + * of receiver window. Check #2. + * + * The scheme does not work when sender sends good segments opening + * window and then starts to feed us spagetti. But it should work + * in common situations. Otherwise, we have to rely on queue collapsing. + */ + +/* Slow part of check#2. */ +static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb) +{ + /* Optimize this! */ + int truesize = tcp_win_from_space(skb->truesize)/2; + int window = tcp_full_space(sk)/2; + + while (tp->rcv_ssthresh <= window) { + if (truesize <= skb->len) + return 2*tp->ack.rcv_mss; + + truesize >>= 1; + window >>= 1; + } + return 0; +} + +static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb) +{ + /* Check #1 */ + if (tp->rcv_ssthresh < tp->window_clamp && + (int)tp->rcv_ssthresh < tcp_space(sk) && + !tcp_memory_pressure) { + int incr; + + /* Check #2. Increase window, if skb with such overhead + * will fit to rcvbuf in future. + */ + if (tcp_win_from_space(skb->truesize) <= skb->len) + incr = 2*tp->advmss; + else + incr = __tcp_grow_window(sk, tp, skb); + + if (incr) { + tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); + tp->ack.quick |= 1; + } + } +} + +/* 3. Tuning rcvbuf, when connection enters established state. */ + +static void tcp_fixup_rcvbuf(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); + + /* Try to select rcvbuf so that 4 mss-sized segments + * will fit to window and correspoding skbs will fit to our rcvbuf. + * (was 3; 4 is minimum to allow fast retransmit to work.) + */ + while (tcp_win_from_space(rcvmem) < tp->advmss) + rcvmem += 128; + if (sk->sk_rcvbuf < 4 * rcvmem) + sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); +} + +/* 4. Try to fixup all. It is made iimediately after connection enters + * established state. + */ +static void tcp_init_buffer_space(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int maxwin; + + if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) + tcp_fixup_rcvbuf(sk); + if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) + tcp_fixup_sndbuf(sk); + + tp->rcvq_space.space = tp->rcv_wnd; + + maxwin = tcp_full_space(sk); + + if (tp->window_clamp >= maxwin) { + tp->window_clamp = maxwin; + + if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) + tp->window_clamp = max(maxwin - + (maxwin >> sysctl_tcp_app_win), + 4 * tp->advmss); + } + + /* Force reservation of one segment. */ + if (sysctl_tcp_app_win && + tp->window_clamp > 2 * tp->advmss && + tp->window_clamp + tp->advmss > maxwin) + tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); + + tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static void init_bictcp(struct tcp_sock *tp) +{ + tp->bictcp.cnt = 0; + + tp->bictcp.last_max_cwnd = 0; + tp->bictcp.last_cwnd = 0; + tp->bictcp.last_stamp = 0; +} + +/* 5. Recalculate window clamp after socket hit its memory bounds. */ +static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) +{ + struct sk_buff *skb; + unsigned int app_win = tp->rcv_nxt - tp->copied_seq; + int ofo_win = 0; + + tp->ack.quick = 0; + + skb_queue_walk(&tp->out_of_order_queue, skb) { + ofo_win += skb->len; + } + + /* If overcommit is due to out of order segments, + * do not clamp window. Try to expand rcvbuf instead. + */ + if (ofo_win) { + if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && + !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && + !tcp_memory_pressure && + atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) + sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), + sysctl_tcp_rmem[2]); + } + if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) { + app_win += ofo_win; + if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf) + app_win >>= 1; + if (app_win > tp->ack.rcv_mss) + app_win -= tp->ack.rcv_mss; + app_win = max(app_win, 2U*tp->advmss); + + if (!ofo_win) + tp->window_clamp = min(tp->window_clamp, app_win); + tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); + } +} + +/* Receiver "autotuning" code. + * + * The algorithm for RTT estimation w/o timestamps is based on + * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. + * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> + * + * More detail on this code can be found at + * <http://www.psc.edu/~jheffner/senior_thesis.ps>, + * though this reference is out of date. A new paper + * is pending. + */ +static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) +{ + u32 new_sample = tp->rcv_rtt_est.rtt; + long m = sample; + + if (m == 0) + m = 1; + + if (new_sample != 0) { + /* If we sample in larger samples in the non-timestamp + * case, we could grossly overestimate the RTT especially + * with chatty applications or bulk transfer apps which + * are stalled on filesystem I/O. + * + * Also, since we are only going for a minimum in the + * non-timestamp case, we do not smoothe things out + * else with timestamps disabled convergance takes too + * long. + */ + if (!win_dep) { + m -= (new_sample >> 3); + new_sample += m; + } else if (m < new_sample) + new_sample = m << 3; + } else { + /* No previous mesaure. */ + new_sample = m << 3; + } + + if (tp->rcv_rtt_est.rtt != new_sample) + tp->rcv_rtt_est.rtt = new_sample; +} + +static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) +{ + if (tp->rcv_rtt_est.time == 0) + goto new_measure; + if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) + return; + tcp_rcv_rtt_update(tp, + jiffies - tp->rcv_rtt_est.time, + 1); + +new_measure: + tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; + tp->rcv_rtt_est.time = tcp_time_stamp; +} + +static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb) +{ + if (tp->rx_opt.rcv_tsecr && + (TCP_SKB_CB(skb)->end_seq - + TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss)) + tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); +} + +/* + * This function should be called every time data is copied to user space. + * It calculates the appropriate TCP receive buffer space. + */ +void tcp_rcv_space_adjust(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int time; + int space; + + if (tp->rcvq_space.time == 0) + goto new_measure; + + time = tcp_time_stamp - tp->rcvq_space.time; + if (time < (tp->rcv_rtt_est.rtt >> 3) || + tp->rcv_rtt_est.rtt == 0) + return; + + space = 2 * (tp->copied_seq - tp->rcvq_space.seq); + + space = max(tp->rcvq_space.space, space); + + if (tp->rcvq_space.space != space) { + int rcvmem; + + tp->rcvq_space.space = space; + + if (sysctl_tcp_moderate_rcvbuf) { + int new_clamp = space; + + /* Receive space grows, normalize in order to + * take into account packet headers and sk_buff + * structure overhead. + */ + space /= tp->advmss; + if (!space) + space = 1; + rcvmem = (tp->advmss + MAX_TCP_HEADER + + 16 + sizeof(struct sk_buff)); + while (tcp_win_from_space(rcvmem) < tp->advmss) + rcvmem += 128; + space *= rcvmem; + space = min(space, sysctl_tcp_rmem[2]); + if (space > sk->sk_rcvbuf) { + sk->sk_rcvbuf = space; + + /* Make the window clamp follow along. */ + tp->window_clamp = new_clamp; + } + } + } + +new_measure: + tp->rcvq_space.seq = tp->copied_seq; + tp->rcvq_space.time = tcp_time_stamp; +} + +/* There is something which you must keep in mind when you analyze the + * behavior of the tp->ato delayed ack timeout interval. When a + * connection starts up, we want to ack as quickly as possible. The + * problem is that "good" TCP's do slow start at the beginning of data + * transmission. The means that until we send the first few ACK's the + * sender will sit on his end and only queue most of his data, because + * he can only send snd_cwnd unacked packets at any given time. For + * each ACK we send, he increments snd_cwnd and transmits more of his + * queue. -DaveM + */ +static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) +{ + u32 now; + + tcp_schedule_ack(tp); + + tcp_measure_rcv_mss(tp, skb); + + tcp_rcv_rtt_measure(tp); + + now = tcp_time_stamp; + + if (!tp->ack.ato) { + /* The _first_ data packet received, initialize + * delayed ACK engine. + */ + tcp_incr_quickack(tp); + tp->ack.ato = TCP_ATO_MIN; + } else { + int m = now - tp->ack.lrcvtime; + + if (m <= TCP_ATO_MIN/2) { + /* The fastest case is the first. */ + tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2; + } else if (m < tp->ack.ato) { + tp->ack.ato = (tp->ack.ato>>1) + m; + if (tp->ack.ato > tp->rto) + tp->ack.ato = tp->rto; + } else if (m > tp->rto) { + /* Too long gap. Apparently sender falled to + * restart window, so that we send ACKs quickly. + */ + tcp_incr_quickack(tp); + sk_stream_mem_reclaim(sk); + } + } + tp->ack.lrcvtime = now; + + TCP_ECN_check_ce(tp, skb); + + if (skb->len >= 128) + tcp_grow_window(sk, tp, skb); +} + +/* When starting a new connection, pin down the current choice of + * congestion algorithm. + */ +void tcp_ca_init(struct tcp_sock *tp) +{ + if (sysctl_tcp_westwood) + tp->adv_cong = TCP_WESTWOOD; + else if (sysctl_tcp_bic) + tp->adv_cong = TCP_BIC; + else if (sysctl_tcp_vegas_cong_avoid) { + tp->adv_cong = TCP_VEGAS; + tp->vegas.baseRTT = 0x7fffffff; + tcp_vegas_enable(tp); + } +} + +/* Do RTT sampling needed for Vegas. + * Basically we: + * o min-filter RTT samples from within an RTT to get the current + * propagation delay + queuing delay (we are min-filtering to try to + * avoid the effects of delayed ACKs) + * o min-filter RTT samples from a much longer window (forever for now) + * to find the propagation delay (baseRTT) + */ +static inline void vegas_rtt_calc(struct tcp_sock *tp, __u32 rtt) +{ + __u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */ + + /* Filter to find propagation delay: */ + if (vrtt < tp->vegas.baseRTT) + tp->vegas.baseRTT = vrtt; + + /* Find the min RTT during the last RTT to find + * the current prop. delay + queuing delay: + */ + tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt); + tp->vegas.cntRTT++; +} + +/* Called to compute a smoothed rtt estimate. The data fed to this + * routine either comes from timestamps, or from segments that were + * known _not_ to have been retransmitted [see Karn/Partridge + * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 + * piece by Van Jacobson. + * NOTE: the next three routines used to be one big routine. + * To save cycles in the RFC 1323 implementation it was better to break + * it up into three procedures. -- erics + */ +static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt) +{ + long m = mrtt; /* RTT */ + + if (tcp_vegas_enabled(tp)) + vegas_rtt_calc(tp, mrtt); + + /* The following amusing code comes from Jacobson's + * article in SIGCOMM '88. Note that rtt and mdev + * are scaled versions of rtt and mean deviation. + * This is designed to be as fast as possible + * m stands for "measurement". + * + * On a 1990 paper the rto value is changed to: + * RTO = rtt + 4 * mdev + * + * Funny. This algorithm seems to be very broken. + * These formulae increase RTO, when it should be decreased, increase + * too slowly, when it should be incresed fastly, decrease too fastly + * etc. I guess in BSD RTO takes ONE value, so that it is absolutely + * does not matter how to _calculate_ it. Seems, it was trap + * that VJ failed to avoid. 8) + */ + if(m == 0) + m = 1; + if (tp->srtt != 0) { + m -= (tp->srtt >> 3); /* m is now error in rtt est */ + tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ + if (m < 0) { + m = -m; /* m is now abs(error) */ + m -= (tp->mdev >> 2); /* similar update on mdev */ + /* This is similar to one of Eifel findings. + * Eifel blocks mdev updates when rtt decreases. + * This solution is a bit different: we use finer gain + * for mdev in this case (alpha*beta). + * Like Eifel it also prevents growth of rto, + * but also it limits too fast rto decreases, + * happening in pure Eifel. + */ + if (m > 0) + m >>= 3; + } else { + m -= (tp->mdev >> 2); /* similar update on mdev */ + } + tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ + if (tp->mdev > tp->mdev_max) { + tp->mdev_max = tp->mdev; + if (tp->mdev_max > tp->rttvar) + tp->rttvar = tp->mdev_max; + } + if (after(tp->snd_una, tp->rtt_seq)) { + if (tp->mdev_max < tp->rttvar) + tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; + tp->rtt_seq = tp->snd_nxt; + tp->mdev_max = TCP_RTO_MIN; + } + } else { + /* no previous measure. */ + tp->srtt = m<<3; /* take the measured time to be rtt */ + tp->mdev = m<<1; /* make sure rto = 3*rtt */ + tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); + tp->rtt_seq = tp->snd_nxt; + } + + tcp_westwood_update_rtt(tp, tp->srtt >> 3); +} + +/* Calculate rto without backoff. This is the second half of Van Jacobson's + * routine referred to above. + */ +static inline void tcp_set_rto(struct tcp_sock *tp) +{ + /* Old crap is replaced with new one. 8) + * + * More seriously: + * 1. If rtt variance happened to be less 50msec, it is hallucination. + * It cannot be less due to utterly erratic ACK generation made + * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ + * to do with delayed acks, because at cwnd>2 true delack timeout + * is invisible. Actually, Linux-2.4 also generates erratic + * ACKs in some curcumstances. + */ + tp->rto = (tp->srtt >> 3) + tp->rttvar; + + /* 2. Fixups made earlier cannot be right. + * If we do not estimate RTO correctly without them, + * all the algo is pure shit and should be replaced + * with correct one. It is exaclty, which we pretend to do. + */ +} + +/* NOTE: clamping at TCP_RTO_MIN is not required, current algo + * guarantees that rto is higher. + */ +static inline void tcp_bound_rto(struct tcp_sock *tp) +{ + if (tp->rto > TCP_RTO_MAX) + tp->rto = TCP_RTO_MAX; +} + +/* Save metrics learned by this TCP session. + This function is called only, when TCP finishes successfully + i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. + */ +void tcp_update_metrics(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + + if (sysctl_tcp_nometrics_save) + return; + + dst_confirm(dst); + + if (dst && (dst->flags&DST_HOST)) { + int m; + + if (tp->backoff || !tp->srtt) { + /* This session failed to estimate rtt. Why? + * Probably, no packets returned in time. + * Reset our results. + */ + if (!(dst_metric_locked(dst, RTAX_RTT))) + dst->metrics[RTAX_RTT-1] = 0; + return; + } + + m = dst_metric(dst, RTAX_RTT) - tp->srtt; + + /* If newly calculated rtt larger than stored one, + * store new one. Otherwise, use EWMA. Remember, + * rtt overestimation is always better than underestimation. + */ + if (!(dst_metric_locked(dst, RTAX_RTT))) { + if (m <= 0) + dst->metrics[RTAX_RTT-1] = tp->srtt; + else + dst->metrics[RTAX_RTT-1] -= (m>>3); + } + + if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { + if (m < 0) + m = -m; + + /* Scale deviation to rttvar fixed point */ + m >>= 1; + if (m < tp->mdev) + m = tp->mdev; + + if (m >= dst_metric(dst, RTAX_RTTVAR)) + dst->metrics[RTAX_RTTVAR-1] = m; + else + dst->metrics[RTAX_RTTVAR-1] -= + (dst->metrics[RTAX_RTTVAR-1] - m)>>2; + } + + if (tp->snd_ssthresh >= 0xFFFF) { + /* Slow start still did not finish. */ + if (dst_metric(dst, RTAX_SSTHRESH) && + !dst_metric_locked(dst, RTAX_SSTHRESH) && + (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) + dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; + if (!dst_metric_locked(dst, RTAX_CWND) && + tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; + } else if (tp->snd_cwnd > tp->snd_ssthresh && + tp->ca_state == TCP_CA_Open) { + /* Cong. avoidance phase, cwnd is reliable. */ + if (!dst_metric_locked(dst, RTAX_SSTHRESH)) + dst->metrics[RTAX_SSTHRESH-1] = + max(tp->snd_cwnd >> 1, tp->snd_ssthresh); + if (!dst_metric_locked(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; + } else { + /* Else slow start did not finish, cwnd is non-sense, + ssthresh may be also invalid. + */ + if (!dst_metric_locked(dst, RTAX_CWND)) + dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; + if (dst->metrics[RTAX_SSTHRESH-1] && + !dst_metric_locked(dst, RTAX_SSTHRESH) && + tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) + dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; + } + + if (!dst_metric_locked(dst, RTAX_REORDERING)) { + if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && + tp->reordering != sysctl_tcp_reordering) + dst->metrics[RTAX_REORDERING-1] = tp->reordering; + } + } +} + +/* Numbers are taken from RFC2414. */ +__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) +{ + __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); + + if (!cwnd) { + if (tp->mss_cache_std > 1460) + cwnd = 2; + else + cwnd = (tp->mss_cache_std > 1095) ? 3 : 4; + } + return min_t(__u32, cwnd, tp->snd_cwnd_clamp); +} + +/* Initialize metrics on socket. */ + +static void tcp_init_metrics(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + + if (dst == NULL) + goto reset; + + dst_confirm(dst); + + if (dst_metric_locked(dst, RTAX_CWND)) + tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); + if (dst_metric(dst, RTAX_SSTHRESH)) { + tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); + if (tp->snd_ssthresh > tp->snd_cwnd_clamp) + tp->snd_ssthresh = tp->snd_cwnd_clamp; + } + if (dst_metric(dst, RTAX_REORDERING) && + tp->reordering != dst_metric(dst, RTAX_REORDERING)) { + tp->rx_opt.sack_ok &= ~2; + tp->reordering = dst_metric(dst, RTAX_REORDERING); + } + + if (dst_metric(dst, RTAX_RTT) == 0) + goto reset; + + if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) + goto reset; + + /* Initial rtt is determined from SYN,SYN-ACK. + * The segment is small and rtt may appear much + * less than real one. Use per-dst memory + * to make it more realistic. + * + * A bit of theory. RTT is time passed after "normal" sized packet + * is sent until it is ACKed. In normal curcumstances sending small + * packets force peer to delay ACKs and calculation is correct too. + * The algorithm is adaptive and, provided we follow specs, it + * NEVER underestimate RTT. BUT! If peer tries to make some clever + * tricks sort of "quick acks" for time long enough to decrease RTT + * to low value, and then abruptly stops to do it and starts to delay + * ACKs, wait for troubles. + */ + if (dst_metric(dst, RTAX_RTT) > tp->srtt) { + tp->srtt = dst_metric(dst, RTAX_RTT); + tp->rtt_seq = tp->snd_nxt; + } + if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { + tp->mdev = dst_metric(dst, RTAX_RTTVAR); + tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); + } + tcp_set_rto(tp); + tcp_bound_rto(tp); + if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) + goto reset; + tp->snd_cwnd = tcp_init_cwnd(tp, dst); + tp->snd_cwnd_stamp = tcp_time_stamp; + return; + +reset: + /* Play conservative. If timestamps are not + * supported, TCP will fail to recalculate correct + * rtt, if initial rto is too small. FORGET ALL AND RESET! + */ + if (!tp->rx_opt.saw_tstamp && tp->srtt) { + tp->srtt = 0; + tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; + tp->rto = TCP_TIMEOUT_INIT; + } +} + +static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts) +{ + if (metric > tp->reordering) { + tp->reordering = min(TCP_MAX_REORDERING, metric); + + /* This exciting event is worth to be remembered. 8) */ + if (ts) + NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); + else if (IsReno(tp)) + NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); + else if (IsFack(tp)) + NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); + else + NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); +#if FASTRETRANS_DEBUG > 1 + printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", + tp->rx_opt.sack_ok, tp->ca_state, + tp->reordering, + tp->fackets_out, + tp->sacked_out, + tp->undo_marker ? tp->undo_retrans : 0); +#endif + /* Disable FACK yet. */ + tp->rx_opt.sack_ok &= ~2; + } +} + +/* This procedure tags the retransmission queue when SACKs arrive. + * + * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). + * Packets in queue with these bits set are counted in variables + * sacked_out, retrans_out and lost_out, correspondingly. + * + * Valid combinations are: + * Tag InFlight Description + * 0 1 - orig segment is in flight. + * S 0 - nothing flies, orig reached receiver. + * L 0 - nothing flies, orig lost by net. + * R 2 - both orig and retransmit are in flight. + * L|R 1 - orig is lost, retransmit is in flight. + * S|R 1 - orig reached receiver, retrans is still in flight. + * (L|S|R is logically valid, it could occur when L|R is sacked, + * but it is equivalent to plain S and code short-curcuits it to S. + * L|S is logically invalid, it would mean -1 packet in flight 8)) + * + * These 6 states form finite state machine, controlled by the following events: + * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) + * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) + * 3. Loss detection event of one of three flavors: + * A. Scoreboard estimator decided the packet is lost. + * A'. Reno "three dupacks" marks head of queue lost. + * A''. Its FACK modfication, head until snd.fack is lost. + * B. SACK arrives sacking data transmitted after never retransmitted + * hole was sent out. + * C. SACK arrives sacking SND.NXT at the moment, when the + * segment was retransmitted. + * 4. D-SACK added new rule: D-SACK changes any tag to S. + * + * It is pleasant to note, that state diagram turns out to be commutative, + * so that we are allowed not to be bothered by order of our actions, + * when multiple events arrive simultaneously. (see the function below). + * + * Reordering detection. + * -------------------- + * Reordering metric is maximal distance, which a packet can be displaced + * in packet stream. With SACKs we can estimate it: + * + * 1. SACK fills old hole and the corresponding segment was not + * ever retransmitted -> reordering. Alas, we cannot use it + * when segment was retransmitted. + * 2. The last flaw is solved with D-SACK. D-SACK arrives + * for retransmitted and already SACKed segment -> reordering.. + * Both of these heuristics are not used in Loss state, when we cannot + * account for retransmits accurately. + */ +static int +tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked; + struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2); + int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; + int reord = tp->packets_out; + int prior_fackets; + u32 lost_retrans = 0; + int flag = 0; + int i; + + /* So, SACKs for already sent large segments will be lost. + * Not good, but alternative is to resegment the queue. */ + if (sk->sk_route_caps & NETIF_F_TSO) { + sk->sk_route_caps &= ~NETIF_F_TSO; + sock_set_flag(sk, SOCK_NO_LARGESEND); + tp->mss_cache = tp->mss_cache_std; + } + + if (!tp->sacked_out) + tp->fackets_out = 0; + prior_fackets = tp->fackets_out; + + for (i=0; i<num_sacks; i++, sp++) { + struct sk_buff *skb; + __u32 start_seq = ntohl(sp->start_seq); + __u32 end_seq = ntohl(sp->end_seq); + int fack_count = 0; + int dup_sack = 0; + + /* Check for D-SACK. */ + if (i == 0) { + u32 ack = TCP_SKB_CB(ack_skb)->ack_seq; + + if (before(start_seq, ack)) { + dup_sack = 1; + tp->rx_opt.sack_ok |= 4; + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); + } else if (num_sacks > 1 && + !after(end_seq, ntohl(sp[1].end_seq)) && + !before(start_seq, ntohl(sp[1].start_seq))) { + dup_sack = 1; + tp->rx_opt.sack_ok |= 4; + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); + } + + /* D-SACK for already forgotten data... + * Do dumb counting. */ + if (dup_sack && + !after(end_seq, prior_snd_una) && + after(end_seq, tp->undo_marker)) + tp->undo_retrans--; + + /* Eliminate too old ACKs, but take into + * account more or less fresh ones, they can + * contain valid SACK info. + */ + if (before(ack, prior_snd_una - tp->max_window)) + return 0; + } + + /* Event "B" in the comment above. */ + if (after(end_seq, tp->high_seq)) + flag |= FLAG_DATA_LOST; + + sk_stream_for_retrans_queue(skb, sk) { + u8 sacked = TCP_SKB_CB(skb)->sacked; + int in_sack; + + /* The retransmission queue is always in order, so + * we can short-circuit the walk early. + */ + if(!before(TCP_SKB_CB(skb)->seq, end_seq)) + break; + + fack_count += tcp_skb_pcount(skb); + + in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && + !before(end_seq, TCP_SKB_CB(skb)->end_seq); + + /* Account D-SACK for retransmitted packet. */ + if ((dup_sack && in_sack) && + (sacked & TCPCB_RETRANS) && + after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) + tp->undo_retrans--; + + /* The frame is ACKed. */ + if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { + if (sacked&TCPCB_RETRANS) { + if ((dup_sack && in_sack) && + (sacked&TCPCB_SACKED_ACKED)) + reord = min(fack_count, reord); + } else { + /* If it was in a hole, we detected reordering. */ + if (fack_count < prior_fackets && + !(sacked&TCPCB_SACKED_ACKED)) + reord = min(fack_count, reord); + } + + /* Nothing to do; acked frame is about to be dropped. */ + continue; + } + + if ((sacked&TCPCB_SACKED_RETRANS) && + after(end_seq, TCP_SKB_CB(skb)->ack_seq) && + (!lost_retrans || after(end_seq, lost_retrans))) + lost_retrans = end_seq; + + if (!in_sack) + continue; + + if (!(sacked&TCPCB_SACKED_ACKED)) { + if (sacked & TCPCB_SACKED_RETRANS) { + /* If the segment is not tagged as lost, + * we do not clear RETRANS, believing + * that retransmission is still in flight. + */ + if (sacked & TCPCB_LOST) { + TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); + tp->lost_out -= tcp_skb_pcount(skb); + tp->retrans_out -= tcp_skb_pcount(skb); + } + } else { + /* New sack for not retransmitted frame, + * which was in hole. It is reordering. + */ + if (!(sacked & TCPCB_RETRANS) && + fack_count < prior_fackets) + reord = min(fack_count, reord); + + if (sacked & TCPCB_LOST) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; + tp->lost_out -= tcp_skb_pcount(skb); + } + } + + TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; + flag |= FLAG_DATA_SACKED; + tp->sacked_out += tcp_skb_pcount(skb); + + if (fack_count > tp->fackets_out) + tp->fackets_out = fack_count; + } else { + if (dup_sack && (sacked&TCPCB_RETRANS)) + reord = min(fack_count, reord); + } + + /* D-SACK. We can detect redundant retransmission + * in S|R and plain R frames and clear it. + * undo_retrans is decreased above, L|R frames + * are accounted above as well. + */ + if (dup_sack && + (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; + tp->retrans_out -= tcp_skb_pcount(skb); + } + } + } + + /* Check for lost retransmit. This superb idea is + * borrowed from "ratehalving". Event "C". + * Later note: FACK people cheated me again 8), + * we have to account for reordering! Ugly, + * but should help. + */ + if (lost_retrans && tp->ca_state == TCP_CA_Recovery) { + struct sk_buff *skb; + + sk_stream_for_retrans_queue(skb, sk) { + if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) + break; + if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) + continue; + if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && + after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && + (IsFack(tp) || + !before(lost_retrans, + TCP_SKB_CB(skb)->ack_seq + tp->reordering * + tp->mss_cache_std))) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; + tp->retrans_out -= tcp_skb_pcount(skb); + + if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { + tp->lost_out += tcp_skb_pcount(skb); + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + flag |= FLAG_DATA_SACKED; + NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); + } + } + } + } + + tp->left_out = tp->sacked_out + tp->lost_out; + + if ((reord < tp->fackets_out) && tp->ca_state != TCP_CA_Loss) + tcp_update_reordering(tp, ((tp->fackets_out + 1) - reord), 0); + +#if FASTRETRANS_DEBUG > 0 + BUG_TRAP((int)tp->sacked_out >= 0); + BUG_TRAP((int)tp->lost_out >= 0); + BUG_TRAP((int)tp->retrans_out >= 0); + BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); +#endif + return flag; +} + +/* RTO occurred, but do not yet enter loss state. Instead, transmit two new + * segments to see from the next ACKs whether any data was really missing. + * If the RTO was spurious, new ACKs should arrive. + */ +void tcp_enter_frto(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + tp->frto_counter = 1; + + if (tp->ca_state <= TCP_CA_Disorder || + tp->snd_una == tp->high_seq || + (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) { + tp->prior_ssthresh = tcp_current_ssthresh(tp); + if (!tcp_westwood_ssthresh(tp)) + tp->snd_ssthresh = tcp_recalc_ssthresh(tp); + } + + /* Have to clear retransmission markers here to keep the bookkeeping + * in shape, even though we are not yet in Loss state. + * If something was really lost, it is eventually caught up + * in tcp_enter_frto_loss. + */ + tp->retrans_out = 0; + tp->undo_marker = tp->snd_una; + tp->undo_retrans = 0; + + sk_stream_for_retrans_queue(skb, sk) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS; + } + tcp_sync_left_out(tp); + + tcp_set_ca_state(tp, TCP_CA_Open); + tp->frto_highmark = tp->snd_nxt; +} + +/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, + * which indicates that we should follow the traditional RTO recovery, + * i.e. mark everything lost and do go-back-N retransmission. + */ +static void tcp_enter_frto_loss(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + int cnt = 0; + + tp->sacked_out = 0; + tp->lost_out = 0; + tp->fackets_out = 0; + + sk_stream_for_retrans_queue(skb, sk) { + cnt += tcp_skb_pcount(skb); + TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; + if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { + + /* Do not mark those segments lost that were + * forward transmitted after RTO + */ + if (!after(TCP_SKB_CB(skb)->end_seq, + tp->frto_highmark)) { + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + tp->lost_out += tcp_skb_pcount(skb); + } + } else { + tp->sacked_out += tcp_skb_pcount(skb); + tp->fackets_out = cnt; + } + } + tcp_sync_left_out(tp); + + tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1; + tp->snd_cwnd_cnt = 0; + tp->snd_cwnd_stamp = tcp_time_stamp; + tp->undo_marker = 0; + tp->frto_counter = 0; + + tp->reordering = min_t(unsigned int, tp->reordering, + sysctl_tcp_reordering); + tcp_set_ca_state(tp, TCP_CA_Loss); + tp->high_seq = tp->frto_highmark; + TCP_ECN_queue_cwr(tp); + + init_bictcp(tp); +} + +void tcp_clear_retrans(struct tcp_sock *tp) +{ + tp->left_out = 0; + tp->retrans_out = 0; + + tp->fackets_out = 0; + tp->sacked_out = 0; + tp->lost_out = 0; + + tp->undo_marker = 0; + tp->undo_retrans = 0; +} + +/* Enter Loss state. If "how" is not zero, forget all SACK information + * and reset tags completely, otherwise preserve SACKs. If receiver + * dropped its ofo queue, we will know this due to reneging detection. + */ +void tcp_enter_loss(struct sock *sk, int how) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + int cnt = 0; + + /* Reduce ssthresh if it has not yet been made inside this window. */ + if (tp->ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || + (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) { + tp->prior_ssthresh = tcp_current_ssthresh(tp); + tp->snd_ssthresh = tcp_recalc_ssthresh(tp); + } + tp->snd_cwnd = 1; + tp->snd_cwnd_cnt = 0; + tp->snd_cwnd_stamp = tcp_time_stamp; + + tcp_clear_retrans(tp); + + /* Push undo marker, if it was plain RTO and nothing + * was retransmitted. */ + if (!how) + tp->undo_marker = tp->snd_una; + + sk_stream_for_retrans_queue(skb, sk) { + cnt += tcp_skb_pcount(skb); + if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) + tp->undo_marker = 0; + TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; + if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + tp->lost_out += tcp_skb_pcount(skb); + } else { + tp->sacked_out += tcp_skb_pcount(skb); + tp->fackets_out = cnt; + } + } + tcp_sync_left_out(tp); + + tp->reordering = min_t(unsigned int, tp->reordering, + sysctl_tcp_reordering); + tcp_set_ca_state(tp, TCP_CA_Loss); + tp->high_seq = tp->snd_nxt; + TCP_ECN_queue_cwr(tp); +} + +static int tcp_check_sack_reneging(struct sock *sk, struct tcp_sock *tp) +{ + struct sk_buff *skb; + + /* If ACK arrived pointing to a remembered SACK, + * it means that our remembered SACKs do not reflect + * real state of receiver i.e. + * receiver _host_ is heavily congested (or buggy). + * Do processing similar to RTO timeout. + */ + if ((skb = skb_peek(&sk->sk_write_queue)) != NULL && + (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { + NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); + + tcp_enter_loss(sk, 1); + tp->retransmits++; + tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue)); + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + return 1; + } + return 0; +} + +static inline int tcp_fackets_out(struct tcp_sock *tp) +{ + return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; +} + +static inline int tcp_skb_timedout(struct tcp_sock *tp, struct sk_buff *skb) +{ + return (tcp_time_stamp - TCP_SKB_CB(skb)->when > tp->rto); +} + +static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp) +{ + return tp->packets_out && + tcp_skb_timedout(tp, skb_peek(&sk->sk_write_queue)); +} + +/* Linux NewReno/SACK/FACK/ECN state machine. + * -------------------------------------- + * + * "Open" Normal state, no dubious events, fast path. + * "Disorder" In all the respects it is "Open", + * but requires a bit more attention. It is entered when + * we see some SACKs or dupacks. It is split of "Open" + * mainly to move some processing from fast path to slow one. + * "CWR" CWND was reduced due to some Congestion Notification event. + * It can be ECN, ICMP source quench, local device congestion. + * "Recovery" CWND was reduced, we are fast-retransmitting. + * "Loss" CWND was reduced due to RTO timeout or SACK reneging. + * + * tcp_fastretrans_alert() is entered: + * - each incoming ACK, if state is not "Open" + * - when arrived ACK is unusual, namely: + * * SACK + * * Duplicate ACK. + * * ECN ECE. + * + * Counting packets in flight is pretty simple. + * + * in_flight = packets_out - left_out + retrans_out + * + * packets_out is SND.NXT-SND.UNA counted in packets. + * + * retrans_out is number of retransmitted segments. + * + * left_out is number of segments left network, but not ACKed yet. + * + * left_out = sacked_out + lost_out + * + * sacked_out: Packets, which arrived to receiver out of order + * and hence not ACKed. With SACKs this number is simply + * amount of SACKed data. Even without SACKs + * it is easy to give pretty reliable estimate of this number, + * counting duplicate ACKs. + * + * lost_out: Packets lost by network. TCP has no explicit + * "loss notification" feedback from network (for now). + * It means that this number can be only _guessed_. + * Actually, it is the heuristics to predict lossage that + * distinguishes different algorithms. + * + * F.e. after RTO, when all the queue is considered as lost, + * lost_out = packets_out and in_flight = retrans_out. + * + * Essentially, we have now two algorithms counting + * lost packets. + * + * FACK: It is the simplest heuristics. As soon as we decided + * that something is lost, we decide that _all_ not SACKed + * packets until the most forward SACK are lost. I.e. + * lost_out = fackets_out - sacked_out and left_out = fackets_out. + * It is absolutely correct estimate, if network does not reorder + * packets. And it loses any connection to reality when reordering + * takes place. We use FACK by default until reordering + * is suspected on the path to this destination. + * + * NewReno: when Recovery is entered, we assume that one segment + * is lost (classic Reno). While we are in Recovery and + * a partial ACK arrives, we assume that one more packet + * is lost (NewReno). This heuristics are the same in NewReno + * and SACK. + * + * Imagine, that's all! Forget about all this shamanism about CWND inflation + * deflation etc. CWND is real congestion window, never inflated, changes + * only according to classic VJ rules. + * + * Really tricky (and requiring careful tuning) part of algorithm + * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). + * The first determines the moment _when_ we should reduce CWND and, + * hence, slow down forward transmission. In fact, it determines the moment + * when we decide that hole is caused by loss, rather than by a reorder. + * + * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill + * holes, caused by lost packets. + * + * And the most logically complicated part of algorithm is undo + * heuristics. We detect false retransmits due to both too early + * fast retransmit (reordering) and underestimated RTO, analyzing + * timestamps and D-SACKs. When we detect that some segments were + * retransmitted by mistake and CWND reduction was wrong, we undo + * window reduction and abort recovery phase. This logic is hidden + * inside several functions named tcp_try_undo_<something>. + */ + +/* This function decides, when we should leave Disordered state + * and enter Recovery phase, reducing congestion window. + * + * Main question: may we further continue forward transmission + * with the same cwnd? + */ +static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp) +{ + __u32 packets_out; + + /* Trick#1: The loss is proven. */ + if (tp->lost_out) + return 1; + + /* Not-A-Trick#2 : Classic rule... */ + if (tcp_fackets_out(tp) > tp->reordering) + return 1; + + /* Trick#3 : when we use RFC2988 timer restart, fast + * retransmit can be triggered by timeout of queue head. + */ + if (tcp_head_timedout(sk, tp)) + return 1; + + /* Trick#4: It is still not OK... But will it be useful to delay + * recovery more? + */ + packets_out = tp->packets_out; + if (packets_out <= tp->reordering && + tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && + !tcp_may_send_now(sk, tp)) { + /* We have nothing to send. This connection is limited + * either by receiver window or by application. + */ + return 1; + } + + return 0; +} + +/* If we receive more dupacks than we expected counting segments + * in assumption of absent reordering, interpret this as reordering. + * The only another reason could be bug in receiver TCP. + */ +static void tcp_check_reno_reordering(struct tcp_sock *tp, int addend) +{ + u32 holes; + + holes = max(tp->lost_out, 1U); + holes = min(holes, tp->packets_out); + + if ((tp->sacked_out + holes) > tp->packets_out) { + tp->sacked_out = tp->packets_out - holes; + tcp_update_reordering(tp, tp->packets_out+addend, 0); + } +} + +/* Emulate SACKs for SACKless connection: account for a new dupack. */ + +static void tcp_add_reno_sack(struct tcp_sock *tp) +{ + tp->sacked_out++; + tcp_check_reno_reordering(tp, 0); + tcp_sync_left_out(tp); +} + +/* Account for ACK, ACKing some data in Reno Recovery phase. */ + +static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked) +{ + if (acked > 0) { + /* One ACK acked hole. The rest eat duplicate ACKs. */ + if (acked-1 >= tp->sacked_out) + tp->sacked_out = 0; + else + tp->sacked_out -= acked-1; + } + tcp_check_reno_reordering(tp, acked); + tcp_sync_left_out(tp); +} + +static inline void tcp_reset_reno_sack(struct tcp_sock *tp) +{ + tp->sacked_out = 0; + tp->left_out = tp->lost_out; +} + +/* Mark head of queue up as lost. */ +static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp, + int packets, u32 high_seq) +{ + struct sk_buff *skb; + int cnt = packets; + + BUG_TRAP(cnt <= tp->packets_out); + + sk_stream_for_retrans_queue(skb, sk) { + cnt -= tcp_skb_pcount(skb); + if (cnt < 0 || after(TCP_SKB_CB(skb)->end_seq, high_seq)) + break; + if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + tp->lost_out += tcp_skb_pcount(skb); + } + } + tcp_sync_left_out(tp); +} + +/* Account newly detected lost packet(s) */ + +static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp) +{ + if (IsFack(tp)) { + int lost = tp->fackets_out - tp->reordering; + if (lost <= 0) + lost = 1; + tcp_mark_head_lost(sk, tp, lost, tp->high_seq); + } else { + tcp_mark_head_lost(sk, tp, 1, tp->high_seq); + } + + /* New heuristics: it is possible only after we switched + * to restart timer each time when something is ACKed. + * Hence, we can detect timed out packets during fast + * retransmit without falling to slow start. + */ + if (tcp_head_timedout(sk, tp)) { + struct sk_buff *skb; + + sk_stream_for_retrans_queue(skb, sk) { + if (tcp_skb_timedout(tp, skb) && + !(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + tp->lost_out += tcp_skb_pcount(skb); + } + } + tcp_sync_left_out(tp); + } +} + +/* CWND moderation, preventing bursts due to too big ACKs + * in dubious situations. + */ +static inline void tcp_moderate_cwnd(struct tcp_sock *tp) +{ + tp->snd_cwnd = min(tp->snd_cwnd, + tcp_packets_in_flight(tp)+tcp_max_burst(tp)); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +/* Decrease cwnd each second ack. */ + +static void tcp_cwnd_down(struct tcp_sock *tp) +{ + int decr = tp->snd_cwnd_cnt + 1; + __u32 limit; + + /* + * TCP Westwood + * Here limit is evaluated as BWestimation*RTTmin (for obtaining it + * in packets we use mss_cache). If sysctl_tcp_westwood is off + * tcp_westwood_bw_rttmin() returns 0. In such case snd_ssthresh is + * still used as usual. It prevents other strange cases in which + * BWE*RTTmin could assume value 0. It should not happen but... + */ + + if (!(limit = tcp_westwood_bw_rttmin(tp))) + limit = tp->snd_ssthresh/2; + + tp->snd_cwnd_cnt = decr&1; + decr >>= 1; + + if (decr && tp->snd_cwnd > limit) + tp->snd_cwnd -= decr; + + tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +/* Nothing was retransmitted or returned timestamp is less + * than timestamp of the first retransmission. + */ +static inline int tcp_packet_delayed(struct tcp_sock *tp) +{ + return !tp->retrans_stamp || + (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && + (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); +} + +/* Undo procedures. */ + +#if FASTRETRANS_DEBUG > 1 +static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg) +{ + struct inet_sock *inet = inet_sk(sk); + printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", + msg, + NIPQUAD(inet->daddr), ntohs(inet->dport), + tp->snd_cwnd, tp->left_out, + tp->snd_ssthresh, tp->prior_ssthresh, + tp->packets_out); +} +#else +#define DBGUNDO(x...) do { } while (0) +#endif + +static void tcp_undo_cwr(struct tcp_sock *tp, int undo) +{ + if (tp->prior_ssthresh) { + if (tcp_is_bic(tp)) + tp->snd_cwnd = max(tp->snd_cwnd, tp->bictcp.last_max_cwnd); + else + tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); + + if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { + tp->snd_ssthresh = tp->prior_ssthresh; + TCP_ECN_withdraw_cwr(tp); + } + } else { + tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); + } + tcp_moderate_cwnd(tp); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static inline int tcp_may_undo(struct tcp_sock *tp) +{ + return tp->undo_marker && + (!tp->undo_retrans || tcp_packet_delayed(tp)); +} + +/* People celebrate: "We love our President!" */ +static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp) +{ + if (tcp_may_undo(tp)) { + /* Happy end! We did not retransmit anything + * or our original transmission succeeded. + */ + DBGUNDO(sk, tp, tp->ca_state == TCP_CA_Loss ? "loss" : "retrans"); + tcp_undo_cwr(tp, 1); + if (tp->ca_state == TCP_CA_Loss) + NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); + else + NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); + tp->undo_marker = 0; + } + if (tp->snd_una == tp->high_seq && IsReno(tp)) { + /* Hold old state until something *above* high_seq + * is ACKed. For Reno it is MUST to prevent false + * fast retransmits (RFC2582). SACK TCP is safe. */ + tcp_moderate_cwnd(tp); + return 1; + } + tcp_set_ca_state(tp, TCP_CA_Open); + return 0; +} + +/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ +static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp) +{ + if (tp->undo_marker && !tp->undo_retrans) { + DBGUNDO(sk, tp, "D-SACK"); + tcp_undo_cwr(tp, 1); + tp->undo_marker = 0; + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); + } +} + +/* Undo during fast recovery after partial ACK. */ + +static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp, + int acked) +{ + /* Partial ACK arrived. Force Hoe's retransmit. */ + int failed = IsReno(tp) || tp->fackets_out>tp->reordering; + + if (tcp_may_undo(tp)) { + /* Plain luck! Hole if filled with delayed + * packet, rather than with a retransmit. + */ + if (tp->retrans_out == 0) + tp->retrans_stamp = 0; + + tcp_update_reordering(tp, tcp_fackets_out(tp)+acked, 1); + + DBGUNDO(sk, tp, "Hoe"); + tcp_undo_cwr(tp, 0); + NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); + + /* So... Do not make Hoe's retransmit yet. + * If the first packet was delayed, the rest + * ones are most probably delayed as well. + */ + failed = 0; + } + return failed; +} + +/* Undo during loss recovery after partial ACK. */ +static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp) +{ + if (tcp_may_undo(tp)) { + struct sk_buff *skb; + sk_stream_for_retrans_queue(skb, sk) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; + } + DBGUNDO(sk, tp, "partial loss"); + tp->lost_out = 0; + tp->left_out = tp->sacked_out; + tcp_undo_cwr(tp, 1); + NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); + tp->retransmits = 0; + tp->undo_marker = 0; + if (!IsReno(tp)) + tcp_set_ca_state(tp, TCP_CA_Open); + return 1; + } + return 0; +} + +static inline void tcp_complete_cwr(struct tcp_sock *tp) +{ + if (tcp_westwood_cwnd(tp)) + tp->snd_ssthresh = tp->snd_cwnd; + else + tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag) +{ + tp->left_out = tp->sacked_out; + + if (tp->retrans_out == 0) + tp->retrans_stamp = 0; + + if (flag&FLAG_ECE) + tcp_enter_cwr(tp); + + if (tp->ca_state != TCP_CA_CWR) { + int state = TCP_CA_Open; + + if (tp->left_out || tp->retrans_out || tp->undo_marker) + state = TCP_CA_Disorder; + + if (tp->ca_state != state) { + tcp_set_ca_state(tp, state); + tp->high_seq = tp->snd_nxt; + } + tcp_moderate_cwnd(tp); + } else { + tcp_cwnd_down(tp); + } +} + +/* Process an event, which can update packets-in-flight not trivially. + * Main goal of this function is to calculate new estimate for left_out, + * taking into account both packets sitting in receiver's buffer and + * packets lost by network. + * + * Besides that it does CWND reduction, when packet loss is detected + * and changes state of machine. + * + * It does _not_ decide what to send, it is made in function + * tcp_xmit_retransmit_queue(). + */ +static void +tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, + int prior_packets, int flag) +{ + struct tcp_sock *tp = tcp_sk(sk); + int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); + + /* Some technical things: + * 1. Reno does not count dupacks (sacked_out) automatically. */ + if (!tp->packets_out) + tp->sacked_out = 0; + /* 2. SACK counts snd_fack in packets inaccurately. */ + if (tp->sacked_out == 0) + tp->fackets_out = 0; + + /* Now state machine starts. + * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ + if (flag&FLAG_ECE) + tp->prior_ssthresh = 0; + + /* B. In all the states check for reneging SACKs. */ + if (tp->sacked_out && tcp_check_sack_reneging(sk, tp)) + return; + + /* C. Process data loss notification, provided it is valid. */ + if ((flag&FLAG_DATA_LOST) && + before(tp->snd_una, tp->high_seq) && + tp->ca_state != TCP_CA_Open && + tp->fackets_out > tp->reordering) { + tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq); + NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); + } + + /* D. Synchronize left_out to current state. */ + tcp_sync_left_out(tp); + + /* E. Check state exit conditions. State can be terminated + * when high_seq is ACKed. */ + if (tp->ca_state == TCP_CA_Open) { + if (!sysctl_tcp_frto) + BUG_TRAP(tp->retrans_out == 0); + tp->retrans_stamp = 0; + } else if (!before(tp->snd_una, tp->high_seq)) { + switch (tp->ca_state) { + case TCP_CA_Loss: + tp->retransmits = 0; + if (tcp_try_undo_recovery(sk, tp)) + return; + break; + + case TCP_CA_CWR: + /* CWR is to be held something *above* high_seq + * is ACKed for CWR bit to reach receiver. */ + if (tp->snd_una != tp->high_seq) { + tcp_complete_cwr(tp); + tcp_set_ca_state(tp, TCP_CA_Open); + } + break; + + case TCP_CA_Disorder: + tcp_try_undo_dsack(sk, tp); + if (!tp->undo_marker || + /* For SACK case do not Open to allow to undo + * catching for all duplicate ACKs. */ + IsReno(tp) || tp->snd_una != tp->high_seq) { + tp->undo_marker = 0; + tcp_set_ca_state(tp, TCP_CA_Open); + } + break; + + case TCP_CA_Recovery: + if (IsReno(tp)) + tcp_reset_reno_sack(tp); + if (tcp_try_undo_recovery(sk, tp)) + return; + tcp_complete_cwr(tp); + break; + } + } + + /* F. Process state. */ + switch (tp->ca_state) { + case TCP_CA_Recovery: + if (prior_snd_una == tp->snd_una) { + if (IsReno(tp) && is_dupack) + tcp_add_reno_sack(tp); + } else { + int acked = prior_packets - tp->packets_out; + if (IsReno(tp)) + tcp_remove_reno_sacks(sk, tp, acked); + is_dupack = tcp_try_undo_partial(sk, tp, acked); + } + break; + case TCP_CA_Loss: + if (flag&FLAG_DATA_ACKED) + tp->retransmits = 0; + if (!tcp_try_undo_loss(sk, tp)) { + tcp_moderate_cwnd(tp); + tcp_xmit_retransmit_queue(sk); + return; + } + if (tp->ca_state != TCP_CA_Open) + return; + /* Loss is undone; fall through to processing in Open state. */ + default: + if (IsReno(tp)) { + if (tp->snd_una != prior_snd_una) + tcp_reset_reno_sack(tp); + if (is_dupack) + tcp_add_reno_sack(tp); + } + + if (tp->ca_state == TCP_CA_Disorder) + tcp_try_undo_dsack(sk, tp); + + if (!tcp_time_to_recover(sk, tp)) { + tcp_try_to_open(sk, tp, flag); + return; + } + + /* Otherwise enter Recovery state */ + + if (IsReno(tp)) + NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); + else + NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); + + tp->high_seq = tp->snd_nxt; + tp->prior_ssthresh = 0; + tp->undo_marker = tp->snd_una; + tp->undo_retrans = tp->retrans_out; + + if (tp->ca_state < TCP_CA_CWR) { + if (!(flag&FLAG_ECE)) + tp->prior_ssthresh = tcp_current_ssthresh(tp); + tp->snd_ssthresh = tcp_recalc_ssthresh(tp); + TCP_ECN_queue_cwr(tp); + } + + tp->snd_cwnd_cnt = 0; + tcp_set_ca_state(tp, TCP_CA_Recovery); + } + + if (is_dupack || tcp_head_timedout(sk, tp)) + tcp_update_scoreboard(sk, tp); + tcp_cwnd_down(tp); + tcp_xmit_retransmit_queue(sk); +} + +/* Read draft-ietf-tcplw-high-performance before mucking + * with this code. (Superceeds RFC1323) + */ +static void tcp_ack_saw_tstamp(struct tcp_sock *tp, int flag) +{ + __u32 seq_rtt; + + /* RTTM Rule: A TSecr value received in a segment is used to + * update the averaged RTT measurement only if the segment + * acknowledges some new data, i.e., only if it advances the + * left edge of the send window. + * + * See draft-ietf-tcplw-high-performance-00, section 3.3. + * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> + * + * Changed: reset backoff as soon as we see the first valid sample. + * If we do not, we get strongly overstimated rto. With timestamps + * samples are accepted even from very old segments: f.e., when rtt=1 + * increases to 8, we retransmit 5 times and after 8 seconds delayed + * answer arrives rto becomes 120 seconds! If at least one of segments + * in window is lost... Voila. --ANK (010210) + */ + seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; + tcp_rtt_estimator(tp, seq_rtt); + tcp_set_rto(tp); + tp->backoff = 0; + tcp_bound_rto(tp); +} + +static void tcp_ack_no_tstamp(struct tcp_sock *tp, u32 seq_rtt, int flag) +{ + /* We don't have a timestamp. Can only use + * packets that are not retransmitted to determine + * rtt estimates. Also, we must not reset the + * backoff for rto until we get a non-retransmitted + * packet. This allows us to deal with a situation + * where the network delay has increased suddenly. + * I.e. Karn's algorithm. (SIGCOMM '87, p5.) + */ + + if (flag & FLAG_RETRANS_DATA_ACKED) + return; + + tcp_rtt_estimator(tp, seq_rtt); + tcp_set_rto(tp); + tp->backoff = 0; + tcp_bound_rto(tp); +} + +static inline void tcp_ack_update_rtt(struct tcp_sock *tp, + int flag, s32 seq_rtt) +{ + /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ + if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) + tcp_ack_saw_tstamp(tp, flag); + else if (seq_rtt >= 0) + tcp_ack_no_tstamp(tp, seq_rtt, flag); +} + +/* + * Compute congestion window to use. + * + * This is from the implementation of BICTCP in + * Lison-Xu, Kahaled Harfoush, and Injog Rhee. + * "Binary Increase Congestion Control for Fast, Long Distance + * Networks" in InfoComm 2004 + * Available from: + * http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf + * + * Unless BIC is enabled and congestion window is large + * this behaves the same as the original Reno. + */ +static inline __u32 bictcp_cwnd(struct tcp_sock *tp) +{ + /* orignal Reno behaviour */ + if (!tcp_is_bic(tp)) + return tp->snd_cwnd; + + if (tp->bictcp.last_cwnd == tp->snd_cwnd && + (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5)) + return tp->bictcp.cnt; + + tp->bictcp.last_cwnd = tp->snd_cwnd; + tp->bictcp.last_stamp = tcp_time_stamp; + + /* start off normal */ + if (tp->snd_cwnd <= sysctl_tcp_bic_low_window) + tp->bictcp.cnt = tp->snd_cwnd; + + /* binary increase */ + else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd) { + __u32 dist = (tp->bictcp.last_max_cwnd - tp->snd_cwnd) + / BICTCP_B; + + if (dist > BICTCP_MAX_INCREMENT) + /* linear increase */ + tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT; + else if (dist <= 1U) + /* binary search increase */ + tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR + / BICTCP_B; + else + /* binary search increase */ + tp->bictcp.cnt = tp->snd_cwnd / dist; + } else { + /* slow start amd linear increase */ + if (tp->snd_cwnd < tp->bictcp.last_max_cwnd + BICTCP_B) + /* slow start */ + tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR + / BICTCP_B; + else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd + + BICTCP_MAX_INCREMENT*(BICTCP_B-1)) + /* slow start */ + tp->bictcp.cnt = tp->snd_cwnd * (BICTCP_B-1) + / (tp->snd_cwnd-tp->bictcp.last_max_cwnd); + else + /* linear increase */ + tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT; + } + return tp->bictcp.cnt; +} + +/* This is Jacobson's slow start and congestion avoidance. + * SIGCOMM '88, p. 328. + */ +static inline void reno_cong_avoid(struct tcp_sock *tp) +{ + if (tp->snd_cwnd <= tp->snd_ssthresh) { + /* In "safe" area, increase. */ + if (tp->snd_cwnd < tp->snd_cwnd_clamp) + tp->snd_cwnd++; + } else { + /* In dangerous area, increase slowly. + * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd + */ + if (tp->snd_cwnd_cnt >= bictcp_cwnd(tp)) { + if (tp->snd_cwnd < tp->snd_cwnd_clamp) + tp->snd_cwnd++; + tp->snd_cwnd_cnt=0; + } else + tp->snd_cwnd_cnt++; + } + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +/* This is based on the congestion detection/avoidance scheme described in + * Lawrence S. Brakmo and Larry L. Peterson. + * "TCP Vegas: End to end congestion avoidance on a global internet." + * IEEE Journal on Selected Areas in Communication, 13(8):1465--1480, + * October 1995. Available from: + * ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps + * + * See http://www.cs.arizona.edu/xkernel/ for their implementation. + * The main aspects that distinguish this implementation from the + * Arizona Vegas implementation are: + * o We do not change the loss detection or recovery mechanisms of + * Linux in any way. Linux already recovers from losses quite well, + * using fine-grained timers, NewReno, and FACK. + * o To avoid the performance penalty imposed by increasing cwnd + * only every-other RTT during slow start, we increase during + * every RTT during slow start, just like Reno. + * o Largely to allow continuous cwnd growth during slow start, + * we use the rate at which ACKs come back as the "actual" + * rate, rather than the rate at which data is sent. + * o To speed convergence to the right rate, we set the cwnd + * to achieve the right ("actual") rate when we exit slow start. + * o To filter out the noise caused by delayed ACKs, we use the + * minimum RTT sample observed during the last RTT to calculate + * the actual rate. + * o When the sender re-starts from idle, it waits until it has + * received ACKs for an entire flight of new data before making + * a cwnd adjustment decision. The original Vegas implementation + * assumed senders never went idle. + */ +static void vegas_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt) +{ + /* The key players are v_beg_snd_una and v_beg_snd_nxt. + * + * These are so named because they represent the approximate values + * of snd_una and snd_nxt at the beginning of the current RTT. More + * precisely, they represent the amount of data sent during the RTT. + * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt, + * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding + * bytes of data have been ACKed during the course of the RTT, giving + * an "actual" rate of: + * + * (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration) + * + * Unfortunately, v_beg_snd_una is not exactly equal to snd_una, + * because delayed ACKs can cover more than one segment, so they + * don't line up nicely with the boundaries of RTTs. + * + * Another unfortunate fact of life is that delayed ACKs delay the + * advance of the left edge of our send window, so that the number + * of bytes we send in an RTT is often less than our cwnd will allow. + * So we keep track of our cwnd separately, in v_beg_snd_cwnd. + */ + + if (after(ack, tp->vegas.beg_snd_nxt)) { + /* Do the Vegas once-per-RTT cwnd adjustment. */ + u32 old_wnd, old_snd_cwnd; + + + /* Here old_wnd is essentially the window of data that was + * sent during the previous RTT, and has all + * been acknowledged in the course of the RTT that ended + * with the ACK we just received. Likewise, old_snd_cwnd + * is the cwnd during the previous RTT. + */ + old_wnd = (tp->vegas.beg_snd_nxt - tp->vegas.beg_snd_una) / + tp->mss_cache_std; + old_snd_cwnd = tp->vegas.beg_snd_cwnd; + + /* Save the extent of the current window so we can use this + * at the end of the next RTT. + */ + tp->vegas.beg_snd_una = tp->vegas.beg_snd_nxt; + tp->vegas.beg_snd_nxt = tp->snd_nxt; + tp->vegas.beg_snd_cwnd = tp->snd_cwnd; + + /* Take into account the current RTT sample too, to + * decrease the impact of delayed acks. This double counts + * this sample since we count it for the next window as well, + * but that's not too awful, since we're taking the min, + * rather than averaging. + */ + vegas_rtt_calc(tp, seq_rtt); + + /* We do the Vegas calculations only if we got enough RTT + * samples that we can be reasonably sure that we got + * at least one RTT sample that wasn't from a delayed ACK. + * If we only had 2 samples total, + * then that means we're getting only 1 ACK per RTT, which + * means they're almost certainly delayed ACKs. + * If we have 3 samples, we should be OK. + */ + + if (tp->vegas.cntRTT <= 2) { + /* We don't have enough RTT samples to do the Vegas + * calculation, so we'll behave like Reno. + */ + if (tp->snd_cwnd > tp->snd_ssthresh) + tp->snd_cwnd++; + } else { + u32 rtt, target_cwnd, diff; + + /* We have enough RTT samples, so, using the Vegas + * algorithm, we determine if we should increase or + * decrease cwnd, and by how much. + */ + + /* Pluck out the RTT we are using for the Vegas + * calculations. This is the min RTT seen during the + * last RTT. Taking the min filters out the effects + * of delayed ACKs, at the cost of noticing congestion + * a bit later. + */ + rtt = tp->vegas.minRTT; + + /* Calculate the cwnd we should have, if we weren't + * going too fast. + * + * This is: + * (actual rate in segments) * baseRTT + * We keep it as a fixed point number with + * V_PARAM_SHIFT bits to the right of the binary point. + */ + target_cwnd = ((old_wnd * tp->vegas.baseRTT) + << V_PARAM_SHIFT) / rtt; + + /* Calculate the difference between the window we had, + * and the window we would like to have. This quantity + * is the "Diff" from the Arizona Vegas papers. + * + * Again, this is a fixed point number with + * V_PARAM_SHIFT bits to the right of the binary + * point. + */ + diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd; + + if (tp->snd_cwnd < tp->snd_ssthresh) { + /* Slow start. */ + if (diff > sysctl_tcp_vegas_gamma) { + /* Going too fast. Time to slow down + * and switch to congestion avoidance. + */ + tp->snd_ssthresh = 2; + + /* Set cwnd to match the actual rate + * exactly: + * cwnd = (actual rate) * baseRTT + * Then we add 1 because the integer + * truncation robs us of full link + * utilization. + */ + tp->snd_cwnd = min(tp->snd_cwnd, + (target_cwnd >> + V_PARAM_SHIFT)+1); + + } + } else { + /* Congestion avoidance. */ + u32 next_snd_cwnd; + + /* Figure out where we would like cwnd + * to be. + */ + if (diff > sysctl_tcp_vegas_beta) { + /* The old window was too fast, so + * we slow down. + */ + next_snd_cwnd = old_snd_cwnd - 1; + } else if (diff < sysctl_tcp_vegas_alpha) { + /* We don't have enough extra packets + * in the network, so speed up. + */ + next_snd_cwnd = old_snd_cwnd + 1; + } else { + /* Sending just as fast as we + * should be. + */ + next_snd_cwnd = old_snd_cwnd; + } + + /* Adjust cwnd upward or downward, toward the + * desired value. + */ + if (next_snd_cwnd > tp->snd_cwnd) + tp->snd_cwnd++; + else if (next_snd_cwnd < tp->snd_cwnd) + tp->snd_cwnd--; + } + } + + /* Wipe the slate clean for the next RTT. */ + tp->vegas.cntRTT = 0; + tp->vegas.minRTT = 0x7fffffff; + } + + /* The following code is executed for every ack we receive, + * except for conditions checked in should_advance_cwnd() + * before the call to tcp_cong_avoid(). Mainly this means that + * we only execute this code if the ack actually acked some + * data. + */ + + /* If we are in slow start, increase our cwnd in response to this ACK. + * (If we are not in slow start then we are in congestion avoidance, + * and adjust our congestion window only once per RTT. See the code + * above.) + */ + if (tp->snd_cwnd <= tp->snd_ssthresh) + tp->snd_cwnd++; + + /* to keep cwnd from growing without bound */ + tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp); + + /* Make sure that we are never so timid as to reduce our cwnd below + * 2 MSS. + * + * Going below 2 MSS would risk huge delayed ACKs from our receiver. + */ + tp->snd_cwnd = max(tp->snd_cwnd, 2U); + + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt) +{ + if (tcp_vegas_enabled(tp)) + vegas_cong_avoid(tp, ack, seq_rtt); + else + reno_cong_avoid(tp); +} + +/* Restart timer after forward progress on connection. + * RFC2988 recommends to restart timer to now+rto. + */ + +static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp) +{ + if (!tp->packets_out) { + tcp_clear_xmit_timer(sk, TCP_TIME_RETRANS); + } else { + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + } +} + +/* There is one downside to this scheme. Although we keep the + * ACK clock ticking, adjusting packet counters and advancing + * congestion window, we do not liberate socket send buffer + * space. + * + * Mucking with skb->truesize and sk->sk_wmem_alloc et al. + * then making a write space wakeup callback is a possible + * future enhancement. WARNING: it is not trivial to make. + */ +static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, + __u32 now, __s32 *seq_rtt) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_skb_cb *scb = TCP_SKB_CB(skb); + __u32 seq = tp->snd_una; + __u32 packets_acked; + int acked = 0; + + /* If we get here, the whole TSO packet has not been + * acked. + */ + BUG_ON(!after(scb->end_seq, seq)); + + packets_acked = tcp_skb_pcount(skb); + if (tcp_trim_head(sk, skb, seq - scb->seq)) + return 0; + packets_acked -= tcp_skb_pcount(skb); + + if (packets_acked) { + __u8 sacked = scb->sacked; + + acked |= FLAG_DATA_ACKED; + if (sacked) { + if (sacked & TCPCB_RETRANS) { + if (sacked & TCPCB_SACKED_RETRANS) + tp->retrans_out -= packets_acked; + acked |= FLAG_RETRANS_DATA_ACKED; + *seq_rtt = -1; + } else if (*seq_rtt < 0) + *seq_rtt = now - scb->when; + if (sacked & TCPCB_SACKED_ACKED) + tp->sacked_out -= packets_acked; + if (sacked & TCPCB_LOST) + tp->lost_out -= packets_acked; + if (sacked & TCPCB_URG) { + if (tp->urg_mode && + !before(seq, tp->snd_up)) + tp->urg_mode = 0; + } + } else if (*seq_rtt < 0) + *seq_rtt = now - scb->when; + + if (tp->fackets_out) { + __u32 dval = min(tp->fackets_out, packets_acked); + tp->fackets_out -= dval; + } + tp->packets_out -= packets_acked; + + BUG_ON(tcp_skb_pcount(skb) == 0); + BUG_ON(!before(scb->seq, scb->end_seq)); + } + + return acked; +} + + +/* Remove acknowledged frames from the retransmission queue. */ +static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + __u32 now = tcp_time_stamp; + int acked = 0; + __s32 seq_rtt = -1; + + while ((skb = skb_peek(&sk->sk_write_queue)) && + skb != sk->sk_send_head) { + struct tcp_skb_cb *scb = TCP_SKB_CB(skb); + __u8 sacked = scb->sacked; + + /* If our packet is before the ack sequence we can + * discard it as it's confirmed to have arrived at + * the other end. + */ + if (after(scb->end_seq, tp->snd_una)) { + if (tcp_skb_pcount(skb) > 1) + acked |= tcp_tso_acked(sk, skb, + now, &seq_rtt); + break; + } + + /* Initial outgoing SYN's get put onto the write_queue + * just like anything else we transmit. It is not + * true data, and if we misinform our callers that + * this ACK acks real data, we will erroneously exit + * connection startup slow start one packet too + * quickly. This is severely frowned upon behavior. + */ + if (!(scb->flags & TCPCB_FLAG_SYN)) { + acked |= FLAG_DATA_ACKED; + } else { + acked |= FLAG_SYN_ACKED; + tp->retrans_stamp = 0; + } + + if (sacked) { + if (sacked & TCPCB_RETRANS) { + if(sacked & TCPCB_SACKED_RETRANS) + tp->retrans_out -= tcp_skb_pcount(skb); + acked |= FLAG_RETRANS_DATA_ACKED; + seq_rtt = -1; + } else if (seq_rtt < 0) + seq_rtt = now - scb->when; + if (sacked & TCPCB_SACKED_ACKED) + tp->sacked_out -= tcp_skb_pcount(skb); + if (sacked & TCPCB_LOST) + tp->lost_out -= tcp_skb_pcount(skb); + if (sacked & TCPCB_URG) { + if (tp->urg_mode && + !before(scb->end_seq, tp->snd_up)) + tp->urg_mode = 0; + } + } else if (seq_rtt < 0) + seq_rtt = now - scb->when; + tcp_dec_pcount_approx(&tp->fackets_out, skb); + tcp_packets_out_dec(tp, skb); + __skb_unlink(skb, skb->list); + sk_stream_free_skb(sk, skb); + } + + if (acked&FLAG_ACKED) { + tcp_ack_update_rtt(tp, acked, seq_rtt); + tcp_ack_packets_out(sk, tp); + } + +#if FASTRETRANS_DEBUG > 0 + BUG_TRAP((int)tp->sacked_out >= 0); + BUG_TRAP((int)tp->lost_out >= 0); + BUG_TRAP((int)tp->retrans_out >= 0); + if (!tp->packets_out && tp->rx_opt.sack_ok) { + if (tp->lost_out) { + printk(KERN_DEBUG "Leak l=%u %d\n", + tp->lost_out, tp->ca_state); + tp->lost_out = 0; + } + if (tp->sacked_out) { + printk(KERN_DEBUG "Leak s=%u %d\n", + tp->sacked_out, tp->ca_state); + tp->sacked_out = 0; + } + if (tp->retrans_out) { + printk(KERN_DEBUG "Leak r=%u %d\n", + tp->retrans_out, tp->ca_state); + tp->retrans_out = 0; + } + } +#endif + *seq_rtt_p = seq_rtt; + return acked; +} + +static void tcp_ack_probe(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Was it a usable window open? */ + + if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq, + tp->snd_una + tp->snd_wnd)) { + tp->backoff = 0; + tcp_clear_xmit_timer(sk, TCP_TIME_PROBE0); + /* Socket must be waked up by subsequent tcp_data_snd_check(). + * This function is not for random using! + */ + } else { + tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0, + min(tp->rto << tp->backoff, TCP_RTO_MAX)); + } +} + +static inline int tcp_ack_is_dubious(struct tcp_sock *tp, int flag) +{ + return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || + tp->ca_state != TCP_CA_Open); +} + +static inline int tcp_may_raise_cwnd(struct tcp_sock *tp, int flag) +{ + return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && + !((1<<tp->ca_state)&(TCPF_CA_Recovery|TCPF_CA_CWR)); +} + +/* Check that window update is acceptable. + * The function assumes that snd_una<=ack<=snd_next. + */ +static inline int tcp_may_update_window(struct tcp_sock *tp, u32 ack, + u32 ack_seq, u32 nwin) +{ + return (after(ack, tp->snd_una) || + after(ack_seq, tp->snd_wl1) || + (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); +} + +/* Update our send window. + * + * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 + * and in FreeBSD. NetBSD's one is even worse.) is wrong. + */ +static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb, u32 ack, u32 ack_seq) +{ + int flag = 0; + u32 nwin = ntohs(skb->h.th->window); + + if (likely(!skb->h.th->syn)) + nwin <<= tp->rx_opt.snd_wscale; + + if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { + flag |= FLAG_WIN_UPDATE; + tcp_update_wl(tp, ack, ack_seq); + + if (tp->snd_wnd != nwin) { + tp->snd_wnd = nwin; + + /* Note, it is the only place, where + * fast path is recovered for sending TCP. + */ + tcp_fast_path_check(sk, tp); + + if (nwin > tp->max_window) { + tp->max_window = nwin; + tcp_sync_mss(sk, tp->pmtu_cookie); + } + } + } + + tp->snd_una = ack; + + return flag; +} + +static void tcp_process_frto(struct sock *sk, u32 prior_snd_una) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tcp_sync_left_out(tp); + + if (tp->snd_una == prior_snd_una || + !before(tp->snd_una, tp->frto_highmark)) { + /* RTO was caused by loss, start retransmitting in + * go-back-N slow start + */ + tcp_enter_frto_loss(sk); + return; + } + + if (tp->frto_counter == 1) { + /* First ACK after RTO advances the window: allow two new + * segments out. + */ + tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; + } else { + /* Also the second ACK after RTO advances the window. + * The RTO was likely spurious. Reduce cwnd and continue + * in congestion avoidance + */ + tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); + tcp_moderate_cwnd(tp); + } + + /* F-RTO affects on two new ACKs following RTO. + * At latest on third ACK the TCP behavor is back to normal. + */ + tp->frto_counter = (tp->frto_counter + 1) % 3; +} + +/* + * TCP Westwood+ + */ + +/* + * @init_westwood + * This function initializes fields used in TCP Westwood+. We can't + * get no information about RTTmin at this time so we simply set it to + * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative + * since in this way we're sure it will be updated in a consistent + * way as soon as possible. It will reasonably happen within the first + * RTT period of the connection lifetime. + */ + +static void init_westwood(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->westwood.bw_ns_est = 0; + tp->westwood.bw_est = 0; + tp->westwood.accounted = 0; + tp->westwood.cumul_ack = 0; + tp->westwood.rtt_win_sx = tcp_time_stamp; + tp->westwood.rtt = TCP_WESTWOOD_INIT_RTT; + tp->westwood.rtt_min = TCP_WESTWOOD_INIT_RTT; + tp->westwood.snd_una = tp->snd_una; +} + +/* + * @westwood_do_filter + * Low-pass filter. Implemented using constant coeffients. + */ + +static inline __u32 westwood_do_filter(__u32 a, __u32 b) +{ + return (((7 * a) + b) >> 3); +} + +static void westwood_filter(struct sock *sk, __u32 delta) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->westwood.bw_ns_est = + westwood_do_filter(tp->westwood.bw_ns_est, + tp->westwood.bk / delta); + tp->westwood.bw_est = + westwood_do_filter(tp->westwood.bw_est, + tp->westwood.bw_ns_est); +} + +/* + * @westwood_update_rttmin + * It is used to update RTTmin. In this case we MUST NOT use + * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN! + */ + +static inline __u32 westwood_update_rttmin(const struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + __u32 rttmin = tp->westwood.rtt_min; + + if (tp->westwood.rtt != 0 && + (tp->westwood.rtt < tp->westwood.rtt_min || !rttmin)) + rttmin = tp->westwood.rtt; + + return rttmin; +} + +/* + * @westwood_acked + * Evaluate increases for dk. + */ + +static inline __u32 westwood_acked(const struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + return tp->snd_una - tp->westwood.snd_una; +} + +/* + * @westwood_new_window + * It evaluates if we are receiving data inside the same RTT window as + * when we started. + * Return value: + * It returns 0 if we are still evaluating samples in the same RTT + * window, 1 if the sample has to be considered in the next window. + */ + +static int westwood_new_window(const struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + __u32 left_bound; + __u32 rtt; + int ret = 0; + + left_bound = tp->westwood.rtt_win_sx; + rtt = max(tp->westwood.rtt, (u32) TCP_WESTWOOD_RTT_MIN); + + /* + * A RTT-window has passed. Be careful since if RTT is less than + * 50ms we don't filter but we continue 'building the sample'. + * This minimum limit was choosen since an estimation on small + * time intervals is better to avoid... + * Obvioulsy on a LAN we reasonably will always have + * right_bound = left_bound + WESTWOOD_RTT_MIN + */ + + if ((left_bound + rtt) < tcp_time_stamp) + ret = 1; + + return ret; +} + +/* + * @westwood_update_window + * It updates RTT evaluation window if it is the right moment to do + * it. If so it calls filter for evaluating bandwidth. + */ + +static void __westwood_update_window(struct sock *sk, __u32 now) +{ + struct tcp_sock *tp = tcp_sk(sk); + __u32 delta = now - tp->westwood.rtt_win_sx; + + if (delta) { + if (tp->westwood.rtt) + westwood_filter(sk, delta); + + tp->westwood.bk = 0; + tp->westwood.rtt_win_sx = tcp_time_stamp; + } +} + + +static void westwood_update_window(struct sock *sk, __u32 now) +{ + if (westwood_new_window(sk)) + __westwood_update_window(sk, now); +} + +/* + * @__tcp_westwood_fast_bw + * It is called when we are in fast path. In particular it is called when + * header prediction is successfull. In such case infact update is + * straight forward and doesn't need any particular care. + */ + +static void __tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + westwood_update_window(sk, tcp_time_stamp); + + tp->westwood.bk += westwood_acked(sk); + tp->westwood.snd_una = tp->snd_una; + tp->westwood.rtt_min = westwood_update_rttmin(sk); +} + +static inline void tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb) +{ + if (tcp_is_westwood(tcp_sk(sk))) + __tcp_westwood_fast_bw(sk, skb); +} + + +/* + * @westwood_dupack_update + * It updates accounted and cumul_ack when receiving a dupack. + */ + +static void westwood_dupack_update(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->westwood.accounted += tp->mss_cache_std; + tp->westwood.cumul_ack = tp->mss_cache_std; +} + +static inline int westwood_may_change_cumul(struct tcp_sock *tp) +{ + return (tp->westwood.cumul_ack > tp->mss_cache_std); +} + +static inline void westwood_partial_update(struct tcp_sock *tp) +{ + tp->westwood.accounted -= tp->westwood.cumul_ack; + tp->westwood.cumul_ack = tp->mss_cache_std; +} + +static inline void westwood_complete_update(struct tcp_sock *tp) +{ + tp->westwood.cumul_ack -= tp->westwood.accounted; + tp->westwood.accounted = 0; +} + +/* + * @westwood_acked_count + * This function evaluates cumul_ack for evaluating dk in case of + * delayed or partial acks. + */ + +static inline __u32 westwood_acked_count(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->westwood.cumul_ack = westwood_acked(sk); + + /* If cumul_ack is 0 this is a dupack since it's not moving + * tp->snd_una. + */ + if (!(tp->westwood.cumul_ack)) + westwood_dupack_update(sk); + + if (westwood_may_change_cumul(tp)) { + /* Partial or delayed ack */ + if (tp->westwood.accounted >= tp->westwood.cumul_ack) + westwood_partial_update(tp); + else + westwood_complete_update(tp); + } + + tp->westwood.snd_una = tp->snd_una; + + return tp->westwood.cumul_ack; +} + + +/* + * @__tcp_westwood_slow_bw + * It is called when something is going wrong..even if there could + * be no problems! Infact a simple delayed packet may trigger a + * dupack. But we need to be careful in such case. + */ + +static void __tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + westwood_update_window(sk, tcp_time_stamp); + + tp->westwood.bk += westwood_acked_count(sk); + tp->westwood.rtt_min = westwood_update_rttmin(sk); +} + +static inline void tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb) +{ + if (tcp_is_westwood(tcp_sk(sk))) + __tcp_westwood_slow_bw(sk, skb); +} + +/* This routine deals with incoming acks, but not outgoing ones. */ +static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 prior_snd_una = tp->snd_una; + u32 ack_seq = TCP_SKB_CB(skb)->seq; + u32 ack = TCP_SKB_CB(skb)->ack_seq; + u32 prior_in_flight; + s32 seq_rtt; + int prior_packets; + + /* If the ack is newer than sent or older than previous acks + * then we can probably ignore it. + */ + if (after(ack, tp->snd_nxt)) + goto uninteresting_ack; + + if (before(ack, prior_snd_una)) + goto old_ack; + + if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { + /* Window is constant, pure forward advance. + * No more checks are required. + * Note, we use the fact that SND.UNA>=SND.WL2. + */ + tcp_update_wl(tp, ack, ack_seq); + tp->snd_una = ack; + tcp_westwood_fast_bw(sk, skb); + flag |= FLAG_WIN_UPDATE; + + NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); + } else { + if (ack_seq != TCP_SKB_CB(skb)->end_seq) + flag |= FLAG_DATA; + else + NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); + + flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq); + + if (TCP_SKB_CB(skb)->sacked) + flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); + + if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th)) + flag |= FLAG_ECE; + + tcp_westwood_slow_bw(sk,skb); + } + + /* We passed data and got it acked, remove any soft error + * log. Something worked... + */ + sk->sk_err_soft = 0; + tp->rcv_tstamp = tcp_time_stamp; + prior_packets = tp->packets_out; + if (!prior_packets) + goto no_queue; + + prior_in_flight = tcp_packets_in_flight(tp); + + /* See if we can take anything off of the retransmit queue. */ + flag |= tcp_clean_rtx_queue(sk, &seq_rtt); + + if (tp->frto_counter) + tcp_process_frto(sk, prior_snd_una); + + if (tcp_ack_is_dubious(tp, flag)) { + /* Advanve CWND, if state allows this. */ + if ((flag & FLAG_DATA_ACKED) && + (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd) && + tcp_may_raise_cwnd(tp, flag)) + tcp_cong_avoid(tp, ack, seq_rtt); + tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); + } else { + if ((flag & FLAG_DATA_ACKED) && + (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd)) + tcp_cong_avoid(tp, ack, seq_rtt); + } + + if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) + dst_confirm(sk->sk_dst_cache); + + return 1; + +no_queue: + tp->probes_out = 0; + + /* If this ack opens up a zero window, clear backoff. It was + * being used to time the probes, and is probably far higher than + * it needs to be for normal retransmission. + */ + if (sk->sk_send_head) + tcp_ack_probe(sk); + return 1; + +old_ack: + if (TCP_SKB_CB(skb)->sacked) + tcp_sacktag_write_queue(sk, skb, prior_snd_una); + +uninteresting_ack: + SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); + return 0; +} + + +/* Look for tcp options. Normally only called on SYN and SYNACK packets. + * But, this can also be called on packets in the established flow when + * the fast version below fails. + */ +void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) +{ + unsigned char *ptr; + struct tcphdr *th = skb->h.th; + int length=(th->doff*4)-sizeof(struct tcphdr); + + ptr = (unsigned char *)(th + 1); + opt_rx->saw_tstamp = 0; + + while(length>0) { + int opcode=*ptr++; + int opsize; + + switch (opcode) { + case TCPOPT_EOL: + return; + case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ + length--; + continue; + default: + opsize=*ptr++; + if (opsize < 2) /* "silly options" */ + return; + if (opsize > length) + return; /* don't parse partial options */ + switch(opcode) { + case TCPOPT_MSS: + if(opsize==TCPOLEN_MSS && th->syn && !estab) { + u16 in_mss = ntohs(get_unaligned((__u16 *)ptr)); + if (in_mss) { + if (opt_rx->user_mss && opt_rx->user_mss < in_mss) + in_mss = opt_rx->user_mss; + opt_rx->mss_clamp = in_mss; + } + } + break; + case TCPOPT_WINDOW: + if(opsize==TCPOLEN_WINDOW && th->syn && !estab) + if (sysctl_tcp_window_scaling) { + __u8 snd_wscale = *(__u8 *) ptr; + opt_rx->wscale_ok = 1; + if (snd_wscale > 14) { + if(net_ratelimit()) + printk(KERN_INFO "tcp_parse_options: Illegal window " + "scaling value %d >14 received.\n", + snd_wscale); + snd_wscale = 14; + } + opt_rx->snd_wscale = snd_wscale; + } + break; + case TCPOPT_TIMESTAMP: + if(opsize==TCPOLEN_TIMESTAMP) { + if ((estab && opt_rx->tstamp_ok) || + (!estab && sysctl_tcp_timestamps)) { + opt_rx->saw_tstamp = 1; + opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr)); + opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4))); + } + } + break; + case TCPOPT_SACK_PERM: + if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { + if (sysctl_tcp_sack) { + opt_rx->sack_ok = 1; + tcp_sack_reset(opt_rx); + } + } + break; + + case TCPOPT_SACK: + if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && + !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && + opt_rx->sack_ok) { + TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; + } + }; + ptr+=opsize-2; + length-=opsize; + }; + } +} + +/* Fast parse options. This hopes to only see timestamps. + * If it is wrong it falls back on tcp_parse_options(). + */ +static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, + struct tcp_sock *tp) +{ + if (th->doff == sizeof(struct tcphdr)>>2) { + tp->rx_opt.saw_tstamp = 0; + return 0; + } else if (tp->rx_opt.tstamp_ok && + th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { + __u32 *ptr = (__u32 *)(th + 1); + if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) + | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { + tp->rx_opt.saw_tstamp = 1; + ++ptr; + tp->rx_opt.rcv_tsval = ntohl(*ptr); + ++ptr; + tp->rx_opt.rcv_tsecr = ntohl(*ptr); + return 1; + } + } + tcp_parse_options(skb, &tp->rx_opt, 1); + return 1; +} + +static inline void tcp_store_ts_recent(struct tcp_sock *tp) +{ + tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; + tp->rx_opt.ts_recent_stamp = xtime.tv_sec; +} + +static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) +{ + if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { + /* PAWS bug workaround wrt. ACK frames, the PAWS discard + * extra check below makes sure this can only happen + * for pure ACK frames. -DaveM + * + * Not only, also it occurs for expired timestamps. + */ + + if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || + xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) + tcp_store_ts_recent(tp); + } +} + +/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM + * + * It is not fatal. If this ACK does _not_ change critical state (seqs, window) + * it can pass through stack. So, the following predicate verifies that + * this segment is not used for anything but congestion avoidance or + * fast retransmit. Moreover, we even are able to eliminate most of such + * second order effects, if we apply some small "replay" window (~RTO) + * to timestamp space. + * + * All these measures still do not guarantee that we reject wrapped ACKs + * on networks with high bandwidth, when sequence space is recycled fastly, + * but it guarantees that such events will be very rare and do not affect + * connection seriously. This doesn't look nice, but alas, PAWS is really + * buggy extension. + * + * [ Later note. Even worse! It is buggy for segments _with_ data. RFC + * states that events when retransmit arrives after original data are rare. + * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is + * the biggest problem on large power networks even with minor reordering. + * OK, let's give it small replay window. If peer clock is even 1hz, it is safe + * up to bandwidth of 18Gigabit/sec. 8) ] + */ + +static int tcp_disordered_ack(struct tcp_sock *tp, struct sk_buff *skb) +{ + struct tcphdr *th = skb->h.th; + u32 seq = TCP_SKB_CB(skb)->seq; + u32 ack = TCP_SKB_CB(skb)->ack_seq; + + return (/* 1. Pure ACK with correct sequence number. */ + (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && + + /* 2. ... and duplicate ACK. */ + ack == tp->snd_una && + + /* 3. ... and does not update window. */ + !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && + + /* 4. ... and sits in replay window. */ + (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (tp->rto*1024)/HZ); +} + +static inline int tcp_paws_discard(struct tcp_sock *tp, struct sk_buff *skb) +{ + return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && + xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && + !tcp_disordered_ack(tp, skb)); +} + +/* Check segment sequence number for validity. + * + * Segment controls are considered valid, if the segment + * fits to the window after truncation to the window. Acceptability + * of data (and SYN, FIN, of course) is checked separately. + * See tcp_data_queue(), for example. + * + * Also, controls (RST is main one) are accepted using RCV.WUP instead + * of RCV.NXT. Peer still did not advance his SND.UNA when we + * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. + * (borrowed from freebsd) + */ + +static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) +{ + return !before(end_seq, tp->rcv_wup) && + !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); +} + +/* When we get a reset we do this. */ +static void tcp_reset(struct sock *sk) +{ + /* We want the right error as BSD sees it (and indeed as we do). */ + switch (sk->sk_state) { + case TCP_SYN_SENT: + sk->sk_err = ECONNREFUSED; + break; + case TCP_CLOSE_WAIT: + sk->sk_err = EPIPE; + break; + case TCP_CLOSE: + return; + default: + sk->sk_err = ECONNRESET; + } + + if (!sock_flag(sk, SOCK_DEAD)) + sk->sk_error_report(sk); + + tcp_done(sk); +} + +/* + * Process the FIN bit. This now behaves as it is supposed to work + * and the FIN takes effect when it is validly part of sequence + * space. Not before when we get holes. + * + * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT + * (and thence onto LAST-ACK and finally, CLOSE, we never enter + * TIME-WAIT) + * + * If we are in FINWAIT-1, a received FIN indicates simultaneous + * close and we go into CLOSING (and later onto TIME-WAIT) + * + * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. + */ +static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tcp_schedule_ack(tp); + + sk->sk_shutdown |= RCV_SHUTDOWN; + sock_set_flag(sk, SOCK_DONE); + + switch (sk->sk_state) { + case TCP_SYN_RECV: + case TCP_ESTABLISHED: + /* Move to CLOSE_WAIT */ + tcp_set_state(sk, TCP_CLOSE_WAIT); + tp->ack.pingpong = 1; + break; + + case TCP_CLOSE_WAIT: + case TCP_CLOSING: + /* Received a retransmission of the FIN, do + * nothing. + */ + break; + case TCP_LAST_ACK: + /* RFC793: Remain in the LAST-ACK state. */ + break; + + case TCP_FIN_WAIT1: + /* This case occurs when a simultaneous close + * happens, we must ack the received FIN and + * enter the CLOSING state. + */ + tcp_send_ack(sk); + tcp_set_state(sk, TCP_CLOSING); + break; + case TCP_FIN_WAIT2: + /* Received a FIN -- send ACK and enter TIME_WAIT. */ + tcp_send_ack(sk); + tcp_time_wait(sk, TCP_TIME_WAIT, 0); + break; + default: + /* Only TCP_LISTEN and TCP_CLOSE are left, in these + * cases we should never reach this piece of code. + */ + printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", + __FUNCTION__, sk->sk_state); + break; + }; + + /* It _is_ possible, that we have something out-of-order _after_ FIN. + * Probably, we should reset in this case. For now drop them. + */ + __skb_queue_purge(&tp->out_of_order_queue); + if (tp->rx_opt.sack_ok) + tcp_sack_reset(&tp->rx_opt); + sk_stream_mem_reclaim(sk); + + if (!sock_flag(sk, SOCK_DEAD)) { + sk->sk_state_change(sk); + + /* Do not send POLL_HUP for half duplex close. */ + if (sk->sk_shutdown == SHUTDOWN_MASK || + sk->sk_state == TCP_CLOSE) + sk_wake_async(sk, 1, POLL_HUP); + else + sk_wake_async(sk, 1, POLL_IN); + } +} + +static __inline__ int +tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) +{ + if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { + if (before(seq, sp->start_seq)) + sp->start_seq = seq; + if (after(end_seq, sp->end_seq)) + sp->end_seq = end_seq; + return 1; + } + return 0; +} + +static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) +{ + if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { + if (before(seq, tp->rcv_nxt)) + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); + else + NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); + + tp->rx_opt.dsack = 1; + tp->duplicate_sack[0].start_seq = seq; + tp->duplicate_sack[0].end_seq = end_seq; + tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); + } +} + +static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) +{ + if (!tp->rx_opt.dsack) + tcp_dsack_set(tp, seq, end_seq); + else + tcp_sack_extend(tp->duplicate_sack, seq, end_seq); +} + +static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && + before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { + NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); + tcp_enter_quickack_mode(tp); + + if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { + u32 end_seq = TCP_SKB_CB(skb)->end_seq; + + if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) + end_seq = tp->rcv_nxt; + tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); + } + } + + tcp_send_ack(sk); +} + +/* These routines update the SACK block as out-of-order packets arrive or + * in-order packets close up the sequence space. + */ +static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) +{ + int this_sack; + struct tcp_sack_block *sp = &tp->selective_acks[0]; + struct tcp_sack_block *swalk = sp+1; + + /* See if the recent change to the first SACK eats into + * or hits the sequence space of other SACK blocks, if so coalesce. + */ + for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { + if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { + int i; + + /* Zap SWALK, by moving every further SACK up by one slot. + * Decrease num_sacks. + */ + tp->rx_opt.num_sacks--; + tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); + for(i=this_sack; i < tp->rx_opt.num_sacks; i++) + sp[i] = sp[i+1]; + continue; + } + this_sack++, swalk++; + } +} + +static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) +{ + __u32 tmp; + + tmp = sack1->start_seq; + sack1->start_seq = sack2->start_seq; + sack2->start_seq = tmp; + + tmp = sack1->end_seq; + sack1->end_seq = sack2->end_seq; + sack2->end_seq = tmp; +} + +static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_sack_block *sp = &tp->selective_acks[0]; + int cur_sacks = tp->rx_opt.num_sacks; + int this_sack; + + if (!cur_sacks) + goto new_sack; + + for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { + if (tcp_sack_extend(sp, seq, end_seq)) { + /* Rotate this_sack to the first one. */ + for (; this_sack>0; this_sack--, sp--) + tcp_sack_swap(sp, sp-1); + if (cur_sacks > 1) + tcp_sack_maybe_coalesce(tp); + return; + } + } + + /* Could not find an adjacent existing SACK, build a new one, + * put it at the front, and shift everyone else down. We + * always know there is at least one SACK present already here. + * + * If the sack array is full, forget about the last one. + */ + if (this_sack >= 4) { + this_sack--; + tp->rx_opt.num_sacks--; + sp--; + } + for(; this_sack > 0; this_sack--, sp--) + *sp = *(sp-1); + +new_sack: + /* Build the new head SACK, and we're done. */ + sp->start_seq = seq; + sp->end_seq = end_seq; + tp->rx_opt.num_sacks++; + tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); +} + +/* RCV.NXT advances, some SACKs should be eaten. */ + +static void tcp_sack_remove(struct tcp_sock *tp) +{ + struct tcp_sack_block *sp = &tp->selective_acks[0]; + int num_sacks = tp->rx_opt.num_sacks; + int this_sack; + + /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ + if (skb_queue_len(&tp->out_of_order_queue) == 0) { + tp->rx_opt.num_sacks = 0; + tp->rx_opt.eff_sacks = tp->rx_opt.dsack; + return; + } + + for(this_sack = 0; this_sack < num_sacks; ) { + /* Check if the start of the sack is covered by RCV.NXT. */ + if (!before(tp->rcv_nxt, sp->start_seq)) { + int i; + + /* RCV.NXT must cover all the block! */ + BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); + + /* Zap this SACK, by moving forward any other SACKS. */ + for (i=this_sack+1; i < num_sacks; i++) + tp->selective_acks[i-1] = tp->selective_acks[i]; + num_sacks--; + continue; + } + this_sack++; + sp++; + } + if (num_sacks != tp->rx_opt.num_sacks) { + tp->rx_opt.num_sacks = num_sacks; + tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); + } +} + +/* This one checks to see if we can put data from the + * out_of_order queue into the receive_queue. + */ +static void tcp_ofo_queue(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + __u32 dsack_high = tp->rcv_nxt; + struct sk_buff *skb; + + while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { + if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) + break; + + if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { + __u32 dsack = dsack_high; + if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) + dsack_high = TCP_SKB_CB(skb)->end_seq; + tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); + } + + if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { + SOCK_DEBUG(sk, "ofo packet was already received \n"); + __skb_unlink(skb, skb->list); + __kfree_skb(skb); + continue; + } + SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", + tp->rcv_nxt, TCP_SKB_CB(skb)->seq, + TCP_SKB_CB(skb)->end_seq); + + __skb_unlink(skb, skb->list); + __skb_queue_tail(&sk->sk_receive_queue, skb); + tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; + if(skb->h.th->fin) + tcp_fin(skb, sk, skb->h.th); + } +} + +static int tcp_prune_queue(struct sock *sk); + +static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) +{ + struct tcphdr *th = skb->h.th; + struct tcp_sock *tp = tcp_sk(sk); + int eaten = -1; + + if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) + goto drop; + + th = skb->h.th; + __skb_pull(skb, th->doff*4); + + TCP_ECN_accept_cwr(tp, skb); + + if (tp->rx_opt.dsack) { + tp->rx_opt.dsack = 0; + tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, + 4 - tp->rx_opt.tstamp_ok); + } + + /* Queue data for delivery to the user. + * Packets in sequence go to the receive queue. + * Out of sequence packets to the out_of_order_queue. + */ + if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { + if (tcp_receive_window(tp) == 0) + goto out_of_window; + + /* Ok. In sequence. In window. */ + if (tp->ucopy.task == current && + tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && + sock_owned_by_user(sk) && !tp->urg_data) { + int chunk = min_t(unsigned int, skb->len, + tp->ucopy.len); + + __set_current_state(TASK_RUNNING); + + local_bh_enable(); + if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { + tp->ucopy.len -= chunk; + tp->copied_seq += chunk; + eaten = (chunk == skb->len && !th->fin); + tcp_rcv_space_adjust(sk); + } + local_bh_disable(); + } + + if (eaten <= 0) { +queue_and_out: + if (eaten < 0 && + (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || + !sk_stream_rmem_schedule(sk, skb))) { + if (tcp_prune_queue(sk) < 0 || + !sk_stream_rmem_schedule(sk, skb)) + goto drop; + } + sk_stream_set_owner_r(skb, sk); + __skb_queue_tail(&sk->sk_receive_queue, skb); + } + tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; + if(skb->len) + tcp_event_data_recv(sk, tp, skb); + if(th->fin) + tcp_fin(skb, sk, th); + + if (skb_queue_len(&tp->out_of_order_queue)) { + tcp_ofo_queue(sk); + + /* RFC2581. 4.2. SHOULD send immediate ACK, when + * gap in queue is filled. + */ + if (!skb_queue_len(&tp->out_of_order_queue)) + tp->ack.pingpong = 0; + } + + if (tp->rx_opt.num_sacks) + tcp_sack_remove(tp); + + tcp_fast_path_check(sk, tp); + + if (eaten > 0) + __kfree_skb(skb); + else if (!sock_flag(sk, SOCK_DEAD)) + sk->sk_data_ready(sk, 0); + return; + } + + if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { + /* A retransmit, 2nd most common case. Force an immediate ack. */ + NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); + tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); + +out_of_window: + tcp_enter_quickack_mode(tp); + tcp_schedule_ack(tp); +drop: + __kfree_skb(skb); + return; + } + + /* Out of window. F.e. zero window probe. */ + if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) + goto out_of_window; + + tcp_enter_quickack_mode(tp); + + if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { + /* Partial packet, seq < rcv_next < end_seq */ + SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", + tp->rcv_nxt, TCP_SKB_CB(skb)->seq, + TCP_SKB_CB(skb)->end_seq); + + tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); + + /* If window is closed, drop tail of packet. But after + * remembering D-SACK for its head made in previous line. + */ + if (!tcp_receive_window(tp)) + goto out_of_window; + goto queue_and_out; + } + + TCP_ECN_check_ce(tp, skb); + + if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || + !sk_stream_rmem_schedule(sk, skb)) { + if (tcp_prune_queue(sk) < 0 || + !sk_stream_rmem_schedule(sk, skb)) + goto drop; + } + + /* Disable header prediction. */ + tp->pred_flags = 0; + tcp_schedule_ack(tp); + + SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", + tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); + + sk_stream_set_owner_r(skb, sk); + + if (!skb_peek(&tp->out_of_order_queue)) { + /* Initial out of order segment, build 1 SACK. */ + if (tp->rx_opt.sack_ok) { + tp->rx_opt.num_sacks = 1; + tp->rx_opt.dsack = 0; + tp->rx_opt.eff_sacks = 1; + tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; + tp->selective_acks[0].end_seq = + TCP_SKB_CB(skb)->end_seq; + } + __skb_queue_head(&tp->out_of_order_queue,skb); + } else { + struct sk_buff *skb1 = tp->out_of_order_queue.prev; + u32 seq = TCP_SKB_CB(skb)->seq; + u32 end_seq = TCP_SKB_CB(skb)->end_seq; + + if (seq == TCP_SKB_CB(skb1)->end_seq) { + __skb_append(skb1, skb); + + if (!tp->rx_opt.num_sacks || + tp->selective_acks[0].end_seq != seq) + goto add_sack; + + /* Common case: data arrive in order after hole. */ + tp->selective_acks[0].end_seq = end_seq; + return; + } + + /* Find place to insert this segment. */ + do { + if (!after(TCP_SKB_CB(skb1)->seq, seq)) + break; + } while ((skb1 = skb1->prev) != + (struct sk_buff*)&tp->out_of_order_queue); + + /* Do skb overlap to previous one? */ + if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && + before(seq, TCP_SKB_CB(skb1)->end_seq)) { + if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { + /* All the bits are present. Drop. */ + __kfree_skb(skb); + tcp_dsack_set(tp, seq, end_seq); + goto add_sack; + } + if (after(seq, TCP_SKB_CB(skb1)->seq)) { + /* Partial overlap. */ + tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); + } else { + skb1 = skb1->prev; + } + } + __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); + + /* And clean segments covered by new one as whole. */ + while ((skb1 = skb->next) != + (struct sk_buff*)&tp->out_of_order_queue && + after(end_seq, TCP_SKB_CB(skb1)->seq)) { + if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { + tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); + break; + } + __skb_unlink(skb1, skb1->list); + tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); + __kfree_skb(skb1); + } + +add_sack: + if (tp->rx_opt.sack_ok) + tcp_sack_new_ofo_skb(sk, seq, end_seq); + } +} + +/* Collapse contiguous sequence of skbs head..tail with + * sequence numbers start..end. + * Segments with FIN/SYN are not collapsed (only because this + * simplifies code) + */ +static void +tcp_collapse(struct sock *sk, struct sk_buff *head, + struct sk_buff *tail, u32 start, u32 end) +{ + struct sk_buff *skb; + + /* First, check that queue is collapsable and find + * the point where collapsing can be useful. */ + for (skb = head; skb != tail; ) { + /* No new bits? It is possible on ofo queue. */ + if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + struct sk_buff *next = skb->next; + __skb_unlink(skb, skb->list); + __kfree_skb(skb); + NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); + skb = next; + continue; + } + + /* The first skb to collapse is: + * - not SYN/FIN and + * - bloated or contains data before "start" or + * overlaps to the next one. + */ + if (!skb->h.th->syn && !skb->h.th->fin && + (tcp_win_from_space(skb->truesize) > skb->len || + before(TCP_SKB_CB(skb)->seq, start) || + (skb->next != tail && + TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) + break; + + /* Decided to skip this, advance start seq. */ + start = TCP_SKB_CB(skb)->end_seq; + skb = skb->next; + } + if (skb == tail || skb->h.th->syn || skb->h.th->fin) + return; + + while (before(start, end)) { + struct sk_buff *nskb; + int header = skb_headroom(skb); + int copy = SKB_MAX_ORDER(header, 0); + + /* Too big header? This can happen with IPv6. */ + if (copy < 0) + return; + if (end-start < copy) + copy = end-start; + nskb = alloc_skb(copy+header, GFP_ATOMIC); + if (!nskb) + return; + skb_reserve(nskb, header); + memcpy(nskb->head, skb->head, header); + nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head); + nskb->h.raw = nskb->head + (skb->h.raw-skb->head); + nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head); + memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); + TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; + __skb_insert(nskb, skb->prev, skb, skb->list); + sk_stream_set_owner_r(nskb, sk); + + /* Copy data, releasing collapsed skbs. */ + while (copy > 0) { + int offset = start - TCP_SKB_CB(skb)->seq; + int size = TCP_SKB_CB(skb)->end_seq - start; + + if (offset < 0) BUG(); + if (size > 0) { + size = min(copy, size); + if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) + BUG(); + TCP_SKB_CB(nskb)->end_seq += size; + copy -= size; + start += size; + } + if (!before(start, TCP_SKB_CB(skb)->end_seq)) { + struct sk_buff *next = skb->next; + __skb_unlink(skb, skb->list); + __kfree_skb(skb); + NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); + skb = next; + if (skb == tail || skb->h.th->syn || skb->h.th->fin) + return; + } + } + } +} + +/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs + * and tcp_collapse() them until all the queue is collapsed. + */ +static void tcp_collapse_ofo_queue(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); + struct sk_buff *head; + u32 start, end; + + if (skb == NULL) + return; + + start = TCP_SKB_CB(skb)->seq; + end = TCP_SKB_CB(skb)->end_seq; + head = skb; + + for (;;) { + skb = skb->next; + + /* Segment is terminated when we see gap or when + * we are at the end of all the queue. */ + if (skb == (struct sk_buff *)&tp->out_of_order_queue || + after(TCP_SKB_CB(skb)->seq, end) || + before(TCP_SKB_CB(skb)->end_seq, start)) { + tcp_collapse(sk, head, skb, start, end); + head = skb; + if (skb == (struct sk_buff *)&tp->out_of_order_queue) + break; + /* Start new segment */ + start = TCP_SKB_CB(skb)->seq; + end = TCP_SKB_CB(skb)->end_seq; + } else { + if (before(TCP_SKB_CB(skb)->seq, start)) + start = TCP_SKB_CB(skb)->seq; + if (after(TCP_SKB_CB(skb)->end_seq, end)) + end = TCP_SKB_CB(skb)->end_seq; + } + } +} + +/* Reduce allocated memory if we can, trying to get + * the socket within its memory limits again. + * + * Return less than zero if we should start dropping frames + * until the socket owning process reads some of the data + * to stabilize the situation. + */ +static int tcp_prune_queue(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); + + NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); + + if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) + tcp_clamp_window(sk, tp); + else if (tcp_memory_pressure) + tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); + + tcp_collapse_ofo_queue(sk); + tcp_collapse(sk, sk->sk_receive_queue.next, + (struct sk_buff*)&sk->sk_receive_queue, + tp->copied_seq, tp->rcv_nxt); + sk_stream_mem_reclaim(sk); + + if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) + return 0; + + /* Collapsing did not help, destructive actions follow. + * This must not ever occur. */ + + /* First, purge the out_of_order queue. */ + if (skb_queue_len(&tp->out_of_order_queue)) { + NET_ADD_STATS_BH(LINUX_MIB_OFOPRUNED, + skb_queue_len(&tp->out_of_order_queue)); + __skb_queue_purge(&tp->out_of_order_queue); + + /* Reset SACK state. A conforming SACK implementation will + * do the same at a timeout based retransmit. When a connection + * is in a sad state like this, we care only about integrity + * of the connection not performance. + */ + if (tp->rx_opt.sack_ok) + tcp_sack_reset(&tp->rx_opt); + sk_stream_mem_reclaim(sk); + } + + if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) + return 0; + + /* If we are really being abused, tell the caller to silently + * drop receive data on the floor. It will get retransmitted + * and hopefully then we'll have sufficient space. + */ + NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); + + /* Massive buffer overcommit. */ + tp->pred_flags = 0; + return -1; +} + + +/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. + * As additional protections, we do not touch cwnd in retransmission phases, + * and if application hit its sndbuf limit recently. + */ +void tcp_cwnd_application_limited(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->ca_state == TCP_CA_Open && + sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { + /* Limited by application or receiver window. */ + u32 win_used = max(tp->snd_cwnd_used, 2U); + if (win_used < tp->snd_cwnd) { + tp->snd_ssthresh = tcp_current_ssthresh(tp); + tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; + } + tp->snd_cwnd_used = 0; + } + tp->snd_cwnd_stamp = tcp_time_stamp; +} + + +/* When incoming ACK allowed to free some skb from write_queue, + * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket + * on the exit from tcp input handler. + * + * PROBLEM: sndbuf expansion does not work well with largesend. + */ +static void tcp_new_space(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->packets_out < tp->snd_cwnd && + !(sk->sk_userlocks & SOCK_SNDBUF_LOCK) && + !tcp_memory_pressure && + atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { + int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache_std) + + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), + demanded = max_t(unsigned int, tp->snd_cwnd, + tp->reordering + 1); + sndmem *= 2*demanded; + if (sndmem > sk->sk_sndbuf) + sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); + tp->snd_cwnd_stamp = tcp_time_stamp; + } + + sk->sk_write_space(sk); +} + +static inline void tcp_check_space(struct sock *sk) +{ + if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { + sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); + if (sk->sk_socket && + test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) + tcp_new_space(sk); + } +} + +static void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) || + tcp_packets_in_flight(tp) >= tp->snd_cwnd || + tcp_write_xmit(sk, tp->nonagle)) + tcp_check_probe_timer(sk, tp); +} + +static __inline__ void tcp_data_snd_check(struct sock *sk) +{ + struct sk_buff *skb = sk->sk_send_head; + + if (skb != NULL) + __tcp_data_snd_check(sk, skb); + tcp_check_space(sk); +} + +/* + * Check if sending an ack is needed. + */ +static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* More than one full frame received... */ + if (((tp->rcv_nxt - tp->rcv_wup) > tp->ack.rcv_mss + /* ... and right edge of window advances far enough. + * (tcp_recvmsg() will send ACK otherwise). Or... + */ + && __tcp_select_window(sk) >= tp->rcv_wnd) || + /* We ACK each frame or... */ + tcp_in_quickack_mode(tp) || + /* We have out of order data. */ + (ofo_possible && + skb_peek(&tp->out_of_order_queue))) { + /* Then ack it now */ + tcp_send_ack(sk); + } else { + /* Else, send delayed ack. */ + tcp_send_delayed_ack(sk); + } +} + +static __inline__ void tcp_ack_snd_check(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + if (!tcp_ack_scheduled(tp)) { + /* We sent a data segment already. */ + return; + } + __tcp_ack_snd_check(sk, 1); +} + +/* + * This routine is only called when we have urgent data + * signalled. Its the 'slow' part of tcp_urg. It could be + * moved inline now as tcp_urg is only called from one + * place. We handle URGent data wrong. We have to - as + * BSD still doesn't use the correction from RFC961. + * For 1003.1g we should support a new option TCP_STDURG to permit + * either form (or just set the sysctl tcp_stdurg). + */ + +static void tcp_check_urg(struct sock * sk, struct tcphdr * th) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 ptr = ntohs(th->urg_ptr); + + if (ptr && !sysctl_tcp_stdurg) + ptr--; + ptr += ntohl(th->seq); + + /* Ignore urgent data that we've already seen and read. */ + if (after(tp->copied_seq, ptr)) + return; + + /* Do not replay urg ptr. + * + * NOTE: interesting situation not covered by specs. + * Misbehaving sender may send urg ptr, pointing to segment, + * which we already have in ofo queue. We are not able to fetch + * such data and will stay in TCP_URG_NOTYET until will be eaten + * by recvmsg(). Seems, we are not obliged to handle such wicked + * situations. But it is worth to think about possibility of some + * DoSes using some hypothetical application level deadlock. + */ + if (before(ptr, tp->rcv_nxt)) + return; + + /* Do we already have a newer (or duplicate) urgent pointer? */ + if (tp->urg_data && !after(ptr, tp->urg_seq)) + return; + + /* Tell the world about our new urgent pointer. */ + sk_send_sigurg(sk); + + /* We may be adding urgent data when the last byte read was + * urgent. To do this requires some care. We cannot just ignore + * tp->copied_seq since we would read the last urgent byte again + * as data, nor can we alter copied_seq until this data arrives + * or we break the sematics of SIOCATMARK (and thus sockatmark()) + * + * NOTE. Double Dutch. Rendering to plain English: author of comment + * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); + * and expect that both A and B disappear from stream. This is _wrong_. + * Though this happens in BSD with high probability, this is occasional. + * Any application relying on this is buggy. Note also, that fix "works" + * only in this artificial test. Insert some normal data between A and B and we will + * decline of BSD again. Verdict: it is better to remove to trap + * buggy users. + */ + if (tp->urg_seq == tp->copied_seq && tp->urg_data && + !sock_flag(sk, SOCK_URGINLINE) && + tp->copied_seq != tp->rcv_nxt) { + struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); + tp->copied_seq++; + if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { + __skb_unlink(skb, skb->list); + __kfree_skb(skb); + } + } + + tp->urg_data = TCP_URG_NOTYET; + tp->urg_seq = ptr; + + /* Disable header prediction. */ + tp->pred_flags = 0; +} + +/* This is the 'fast' part of urgent handling. */ +static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Check if we get a new urgent pointer - normally not. */ + if (th->urg) + tcp_check_urg(sk,th); + + /* Do we wait for any urgent data? - normally not... */ + if (tp->urg_data == TCP_URG_NOTYET) { + u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - + th->syn; + + /* Is the urgent pointer pointing into this packet? */ + if (ptr < skb->len) { + u8 tmp; + if (skb_copy_bits(skb, ptr, &tmp, 1)) + BUG(); + tp->urg_data = TCP_URG_VALID | tmp; + if (!sock_flag(sk, SOCK_DEAD)) + sk->sk_data_ready(sk, 0); + } + } +} + +static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) +{ + struct tcp_sock *tp = tcp_sk(sk); + int chunk = skb->len - hlen; + int err; + + local_bh_enable(); + if (skb->ip_summed==CHECKSUM_UNNECESSARY) + err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); + else + err = skb_copy_and_csum_datagram_iovec(skb, hlen, + tp->ucopy.iov); + + if (!err) { + tp->ucopy.len -= chunk; + tp->copied_seq += chunk; + tcp_rcv_space_adjust(sk); + } + + local_bh_disable(); + return err; +} + +static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) +{ + int result; + + if (sock_owned_by_user(sk)) { + local_bh_enable(); + result = __tcp_checksum_complete(skb); + local_bh_disable(); + } else { + result = __tcp_checksum_complete(skb); + } + return result; +} + +static __inline__ int +tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) +{ + return skb->ip_summed != CHECKSUM_UNNECESSARY && + __tcp_checksum_complete_user(sk, skb); +} + +/* + * TCP receive function for the ESTABLISHED state. + * + * It is split into a fast path and a slow path. The fast path is + * disabled when: + * - A zero window was announced from us - zero window probing + * is only handled properly in the slow path. + * - Out of order segments arrived. + * - Urgent data is expected. + * - There is no buffer space left + * - Unexpected TCP flags/window values/header lengths are received + * (detected by checking the TCP header against pred_flags) + * - Data is sent in both directions. Fast path only supports pure senders + * or pure receivers (this means either the sequence number or the ack + * value must stay constant) + * - Unexpected TCP option. + * + * When these conditions are not satisfied it drops into a standard + * receive procedure patterned after RFC793 to handle all cases. + * The first three cases are guaranteed by proper pred_flags setting, + * the rest is checked inline. Fast processing is turned on in + * tcp_data_queue when everything is OK. + */ +int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, + struct tcphdr *th, unsigned len) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* + * Header prediction. + * The code loosely follows the one in the famous + * "30 instruction TCP receive" Van Jacobson mail. + * + * Van's trick is to deposit buffers into socket queue + * on a device interrupt, to call tcp_recv function + * on the receive process context and checksum and copy + * the buffer to user space. smart... + * + * Our current scheme is not silly either but we take the + * extra cost of the net_bh soft interrupt processing... + * We do checksum and copy also but from device to kernel. + */ + + tp->rx_opt.saw_tstamp = 0; + + /* pred_flags is 0xS?10 << 16 + snd_wnd + * if header_predition is to be made + * 'S' will always be tp->tcp_header_len >> 2 + * '?' will be 0 for the fast path, otherwise pred_flags is 0 to + * turn it off (when there are holes in the receive + * space for instance) + * PSH flag is ignored. + */ + + if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && + TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { + int tcp_header_len = tp->tcp_header_len; + + /* Timestamp header prediction: tcp_header_len + * is automatically equal to th->doff*4 due to pred_flags + * match. + */ + + /* Check timestamp */ + if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { + __u32 *ptr = (__u32 *)(th + 1); + + /* No? Slow path! */ + if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) + | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) + goto slow_path; + + tp->rx_opt.saw_tstamp = 1; + ++ptr; + tp->rx_opt.rcv_tsval = ntohl(*ptr); + ++ptr; + tp->rx_opt.rcv_tsecr = ntohl(*ptr); + + /* If PAWS failed, check it more carefully in slow path */ + if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) + goto slow_path; + + /* DO NOT update ts_recent here, if checksum fails + * and timestamp was corrupted part, it will result + * in a hung connection since we will drop all + * future packets due to the PAWS test. + */ + } + + if (len <= tcp_header_len) { + /* Bulk data transfer: sender */ + if (len == tcp_header_len) { + /* Predicted packet is in window by definition. + * seq == rcv_nxt and rcv_wup <= rcv_nxt. + * Hence, check seq<=rcv_wup reduces to: + */ + if (tcp_header_len == + (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && + tp->rcv_nxt == tp->rcv_wup) + tcp_store_ts_recent(tp); + + tcp_rcv_rtt_measure_ts(tp, skb); + + /* We know that such packets are checksummed + * on entry. + */ + tcp_ack(sk, skb, 0); + __kfree_skb(skb); + tcp_data_snd_check(sk); + return 0; + } else { /* Header too small */ + TCP_INC_STATS_BH(TCP_MIB_INERRS); + goto discard; + } + } else { + int eaten = 0; + + if (tp->ucopy.task == current && + tp->copied_seq == tp->rcv_nxt && + len - tcp_header_len <= tp->ucopy.len && + sock_owned_by_user(sk)) { + __set_current_state(TASK_RUNNING); + + if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) { + /* Predicted packet is in window by definition. + * seq == rcv_nxt and rcv_wup <= rcv_nxt. + * Hence, check seq<=rcv_wup reduces to: + */ + if (tcp_header_len == + (sizeof(struct tcphdr) + + TCPOLEN_TSTAMP_ALIGNED) && + tp->rcv_nxt == tp->rcv_wup) + tcp_store_ts_recent(tp); + + tcp_rcv_rtt_measure_ts(tp, skb); + + __skb_pull(skb, tcp_header_len); + tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; + NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); + eaten = 1; + } + } + if (!eaten) { + if (tcp_checksum_complete_user(sk, skb)) + goto csum_error; + + /* Predicted packet is in window by definition. + * seq == rcv_nxt and rcv_wup <= rcv_nxt. + * Hence, check seq<=rcv_wup reduces to: + */ + if (tcp_header_len == + (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && + tp->rcv_nxt == tp->rcv_wup) + tcp_store_ts_recent(tp); + + tcp_rcv_rtt_measure_ts(tp, skb); + + if ((int)skb->truesize > sk->sk_forward_alloc) + goto step5; + + NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); + + /* Bulk data transfer: receiver */ + __skb_pull(skb,tcp_header_len); + __skb_queue_tail(&sk->sk_receive_queue, skb); + sk_stream_set_owner_r(skb, sk); + tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; + } + + tcp_event_data_recv(sk, tp, skb); + + if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { + /* Well, only one small jumplet in fast path... */ + tcp_ack(sk, skb, FLAG_DATA); + tcp_data_snd_check(sk); + if (!tcp_ack_scheduled(tp)) + goto no_ack; + } + + if (eaten) { + if (tcp_in_quickack_mode(tp)) { + tcp_send_ack(sk); + } else { + tcp_send_delayed_ack(sk); + } + } else { + __tcp_ack_snd_check(sk, 0); + } + +no_ack: + if (eaten) + __kfree_skb(skb); + else + sk->sk_data_ready(sk, 0); + return 0; + } + } + +slow_path: + if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) + goto csum_error; + + /* + * RFC1323: H1. Apply PAWS check first. + */ + if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && + tcp_paws_discard(tp, skb)) { + if (!th->rst) { + NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); + tcp_send_dupack(sk, skb); + goto discard; + } + /* Resets are accepted even if PAWS failed. + + ts_recent update must be made after we are sure + that the packet is in window. + */ + } + + /* + * Standard slow path. + */ + + if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { + /* RFC793, page 37: "In all states except SYN-SENT, all reset + * (RST) segments are validated by checking their SEQ-fields." + * And page 69: "If an incoming segment is not acceptable, + * an acknowledgment should be sent in reply (unless the RST bit + * is set, if so drop the segment and return)". + */ + if (!th->rst) + tcp_send_dupack(sk, skb); + goto discard; + } + + if(th->rst) { + tcp_reset(sk); + goto discard; + } + + tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); + + if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { + TCP_INC_STATS_BH(TCP_MIB_INERRS); + NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); + tcp_reset(sk); + return 1; + } + +step5: + if(th->ack) + tcp_ack(sk, skb, FLAG_SLOWPATH); + + tcp_rcv_rtt_measure_ts(tp, skb); + + /* Process urgent data. */ + tcp_urg(sk, skb, th); + + /* step 7: process the segment text */ + tcp_data_queue(sk, skb); + + tcp_data_snd_check(sk); + tcp_ack_snd_check(sk); + return 0; + +csum_error: + TCP_INC_STATS_BH(TCP_MIB_INERRS); + +discard: + __kfree_skb(skb); + return 0; +} + +static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, + struct tcphdr *th, unsigned len) +{ + struct tcp_sock *tp = tcp_sk(sk); + int saved_clamp = tp->rx_opt.mss_clamp; + + tcp_parse_options(skb, &tp->rx_opt, 0); + + if (th->ack) { + /* rfc793: + * "If the state is SYN-SENT then + * first check the ACK bit + * If the ACK bit is set + * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send + * a reset (unless the RST bit is set, if so drop + * the segment and return)" + * + * We do not send data with SYN, so that RFC-correct + * test reduces to: + */ + if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) + goto reset_and_undo; + + if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && + !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, + tcp_time_stamp)) { + NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); + goto reset_and_undo; + } + + /* Now ACK is acceptable. + * + * "If the RST bit is set + * If the ACK was acceptable then signal the user "error: + * connection reset", drop the segment, enter CLOSED state, + * delete TCB, and return." + */ + + if (th->rst) { + tcp_reset(sk); + goto discard; + } + + /* rfc793: + * "fifth, if neither of the SYN or RST bits is set then + * drop the segment and return." + * + * See note below! + * --ANK(990513) + */ + if (!th->syn) + goto discard_and_undo; + + /* rfc793: + * "If the SYN bit is on ... + * are acceptable then ... + * (our SYN has been ACKed), change the connection + * state to ESTABLISHED..." + */ + + TCP_ECN_rcv_synack(tp, th); + if (tp->ecn_flags&TCP_ECN_OK) + sock_set_flag(sk, SOCK_NO_LARGESEND); + + tp->snd_wl1 = TCP_SKB_CB(skb)->seq; + tcp_ack(sk, skb, FLAG_SLOWPATH); + + /* Ok.. it's good. Set up sequence numbers and + * move to established. + */ + tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; + tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; + + /* RFC1323: The window in SYN & SYN/ACK segments is + * never scaled. + */ + tp->snd_wnd = ntohs(th->window); + tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); + + if (!tp->rx_opt.wscale_ok) { + tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; + tp->window_clamp = min(tp->window_clamp, 65535U); + } + + if (tp->rx_opt.saw_tstamp) { + tp->rx_opt.tstamp_ok = 1; + tp->tcp_header_len = + sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; + tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; + tcp_store_ts_recent(tp); + } else { + tp->tcp_header_len = sizeof(struct tcphdr); + } + + if (tp->rx_opt.sack_ok && sysctl_tcp_fack) + tp->rx_opt.sack_ok |= 2; + + tcp_sync_mss(sk, tp->pmtu_cookie); + tcp_initialize_rcv_mss(sk); + + /* Remember, tcp_poll() does not lock socket! + * Change state from SYN-SENT only after copied_seq + * is initialized. */ + tp->copied_seq = tp->rcv_nxt; + mb(); + tcp_set_state(sk, TCP_ESTABLISHED); + + /* Make sure socket is routed, for correct metrics. */ + tp->af_specific->rebuild_header(sk); + + tcp_init_metrics(sk); + + /* Prevent spurious tcp_cwnd_restart() on first data + * packet. + */ + tp->lsndtime = tcp_time_stamp; + + tcp_init_buffer_space(sk); + + if (sock_flag(sk, SOCK_KEEPOPEN)) + tcp_reset_keepalive_timer(sk, keepalive_time_when(tp)); + + if (!tp->rx_opt.snd_wscale) + __tcp_fast_path_on(tp, tp->snd_wnd); + else + tp->pred_flags = 0; + + if (!sock_flag(sk, SOCK_DEAD)) { + sk->sk_state_change(sk); + sk_wake_async(sk, 0, POLL_OUT); + } + + if (sk->sk_write_pending || tp->defer_accept || tp->ack.pingpong) { + /* Save one ACK. Data will be ready after + * several ticks, if write_pending is set. + * + * It may be deleted, but with this feature tcpdumps + * look so _wonderfully_ clever, that I was not able + * to stand against the temptation 8) --ANK + */ + tcp_schedule_ack(tp); + tp->ack.lrcvtime = tcp_time_stamp; + tp->ack.ato = TCP_ATO_MIN; + tcp_incr_quickack(tp); + tcp_enter_quickack_mode(tp); + tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX); + +discard: + __kfree_skb(skb); + return 0; + } else { + tcp_send_ack(sk); + } + return -1; + } + + /* No ACK in the segment */ + + if (th->rst) { + /* rfc793: + * "If the RST bit is set + * + * Otherwise (no ACK) drop the segment and return." + */ + + goto discard_and_undo; + } + + /* PAWS check. */ + if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) + goto discard_and_undo; + + if (th->syn) { + /* We see SYN without ACK. It is attempt of + * simultaneous connect with crossed SYNs. + * Particularly, it can be connect to self. + */ + tcp_set_state(sk, TCP_SYN_RECV); + + if (tp->rx_opt.saw_tstamp) { + tp->rx_opt.tstamp_ok = 1; + tcp_store_ts_recent(tp); + tp->tcp_header_len = + sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; + } else { + tp->tcp_header_len = sizeof(struct tcphdr); + } + + tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; + tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; + + /* RFC1323: The window in SYN & SYN/ACK segments is + * never scaled. + */ + tp->snd_wnd = ntohs(th->window); + tp->snd_wl1 = TCP_SKB_CB(skb)->seq; + tp->max_window = tp->snd_wnd; + + TCP_ECN_rcv_syn(tp, th); + if (tp->ecn_flags&TCP_ECN_OK) + sock_set_flag(sk, SOCK_NO_LARGESEND); + + tcp_sync_mss(sk, tp->pmtu_cookie); + tcp_initialize_rcv_mss(sk); + + + tcp_send_synack(sk); +#if 0 + /* Note, we could accept data and URG from this segment. + * There are no obstacles to make this. + * + * However, if we ignore data in ACKless segments sometimes, + * we have no reasons to accept it sometimes. + * Also, seems the code doing it in step6 of tcp_rcv_state_process + * is not flawless. So, discard packet for sanity. + * Uncomment this return to process the data. + */ + return -1; +#else + goto discard; +#endif + } + /* "fifth, if neither of the SYN or RST bits is set then + * drop the segment and return." + */ + +discard_and_undo: + tcp_clear_options(&tp->rx_opt); + tp->rx_opt.mss_clamp = saved_clamp; + goto discard; + +reset_and_undo: + tcp_clear_options(&tp->rx_opt); + tp->rx_opt.mss_clamp = saved_clamp; + return 1; +} + + +/* + * This function implements the receiving procedure of RFC 793 for + * all states except ESTABLISHED and TIME_WAIT. + * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be + * address independent. + */ + +int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, + struct tcphdr *th, unsigned len) +{ + struct tcp_sock *tp = tcp_sk(sk); + int queued = 0; + + tp->rx_opt.saw_tstamp = 0; + + switch (sk->sk_state) { + case TCP_CLOSE: + goto discard; + + case TCP_LISTEN: + if(th->ack) + return 1; + + if(th->rst) + goto discard; + + if(th->syn) { + if(tp->af_specific->conn_request(sk, skb) < 0) + return 1; + + init_westwood(sk); + init_bictcp(tp); + + /* Now we have several options: In theory there is + * nothing else in the frame. KA9Q has an option to + * send data with the syn, BSD accepts data with the + * syn up to the [to be] advertised window and + * Solaris 2.1 gives you a protocol error. For now + * we just ignore it, that fits the spec precisely + * and avoids incompatibilities. It would be nice in + * future to drop through and process the data. + * + * Now that TTCP is starting to be used we ought to + * queue this data. + * But, this leaves one open to an easy denial of + * service attack, and SYN cookies can't defend + * against this problem. So, we drop the data + * in the interest of security over speed. + */ + goto discard; + } + goto discard; + + case TCP_SYN_SENT: + init_westwood(sk); + init_bictcp(tp); + + queued = tcp_rcv_synsent_state_process(sk, skb, th, len); + if (queued >= 0) + return queued; + + /* Do step6 onward by hand. */ + tcp_urg(sk, skb, th); + __kfree_skb(skb); + tcp_data_snd_check(sk); + return 0; + } + + if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && + tcp_paws_discard(tp, skb)) { + if (!th->rst) { + NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); + tcp_send_dupack(sk, skb); + goto discard; + } + /* Reset is accepted even if it did not pass PAWS. */ + } + + /* step 1: check sequence number */ + if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { + if (!th->rst) + tcp_send_dupack(sk, skb); + goto discard; + } + + /* step 2: check RST bit */ + if(th->rst) { + tcp_reset(sk); + goto discard; + } + + tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); + + /* step 3: check security and precedence [ignored] */ + + /* step 4: + * + * Check for a SYN in window. + */ + if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { + NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); + tcp_reset(sk); + return 1; + } + + /* step 5: check the ACK field */ + if (th->ack) { + int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); + + switch(sk->sk_state) { + case TCP_SYN_RECV: + if (acceptable) { + tp->copied_seq = tp->rcv_nxt; + mb(); + tcp_set_state(sk, TCP_ESTABLISHED); + sk->sk_state_change(sk); + + /* Note, that this wakeup is only for marginal + * crossed SYN case. Passively open sockets + * are not waked up, because sk->sk_sleep == + * NULL and sk->sk_socket == NULL. + */ + if (sk->sk_socket) { + sk_wake_async(sk,0,POLL_OUT); + } + + tp->snd_una = TCP_SKB_CB(skb)->ack_seq; + tp->snd_wnd = ntohs(th->window) << + tp->rx_opt.snd_wscale; + tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, + TCP_SKB_CB(skb)->seq); + + /* tcp_ack considers this ACK as duplicate + * and does not calculate rtt. + * Fix it at least with timestamps. + */ + if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && + !tp->srtt) + tcp_ack_saw_tstamp(tp, 0); + + if (tp->rx_opt.tstamp_ok) + tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; + + /* Make sure socket is routed, for + * correct metrics. + */ + tp->af_specific->rebuild_header(sk); + + tcp_init_metrics(sk); + + /* Prevent spurious tcp_cwnd_restart() on + * first data packet. + */ + tp->lsndtime = tcp_time_stamp; + + tcp_initialize_rcv_mss(sk); + tcp_init_buffer_space(sk); + tcp_fast_path_on(tp); + } else { + return 1; + } + break; + + case TCP_FIN_WAIT1: + if (tp->snd_una == tp->write_seq) { + tcp_set_state(sk, TCP_FIN_WAIT2); + sk->sk_shutdown |= SEND_SHUTDOWN; + dst_confirm(sk->sk_dst_cache); + + if (!sock_flag(sk, SOCK_DEAD)) + /* Wake up lingering close() */ + sk->sk_state_change(sk); + else { + int tmo; + + if (tp->linger2 < 0 || + (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && + after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { + tcp_done(sk); + NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); + return 1; + } + + tmo = tcp_fin_time(tp); + if (tmo > TCP_TIMEWAIT_LEN) { + tcp_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); + } else if (th->fin || sock_owned_by_user(sk)) { + /* Bad case. We could lose such FIN otherwise. + * It is not a big problem, but it looks confusing + * and not so rare event. We still can lose it now, + * if it spins in bh_lock_sock(), but it is really + * marginal case. + */ + tcp_reset_keepalive_timer(sk, tmo); + } else { + tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); + goto discard; + } + } + } + break; + + case TCP_CLOSING: + if (tp->snd_una == tp->write_seq) { + tcp_time_wait(sk, TCP_TIME_WAIT, 0); + goto discard; + } + break; + + case TCP_LAST_ACK: + if (tp->snd_una == tp->write_seq) { + tcp_update_metrics(sk); + tcp_done(sk); + goto discard; + } + break; + } + } else + goto discard; + + /* step 6: check the URG bit */ + tcp_urg(sk, skb, th); + + /* step 7: process the segment text */ + switch (sk->sk_state) { + case TCP_CLOSE_WAIT: + case TCP_CLOSING: + case TCP_LAST_ACK: + if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) + break; + case TCP_FIN_WAIT1: + case TCP_FIN_WAIT2: + /* RFC 793 says to queue data in these states, + * RFC 1122 says we MUST send a reset. + * BSD 4.4 also does reset. + */ + if (sk->sk_shutdown & RCV_SHUTDOWN) { + if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && + after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { + NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); + tcp_reset(sk); + return 1; + } + } + /* Fall through */ + case TCP_ESTABLISHED: + tcp_data_queue(sk, skb); + queued = 1; + break; + } + + /* tcp_data could move socket to TIME-WAIT */ + if (sk->sk_state != TCP_CLOSE) { + tcp_data_snd_check(sk); + tcp_ack_snd_check(sk); + } + + if (!queued) { +discard: + __kfree_skb(skb); + } + return 0; +} + +EXPORT_SYMBOL(sysctl_tcp_ecn); +EXPORT_SYMBOL(sysctl_tcp_reordering); +EXPORT_SYMBOL(tcp_parse_options); +EXPORT_SYMBOL(tcp_rcv_established); +EXPORT_SYMBOL(tcp_rcv_state_process); |