diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 1739 |
1 files changed, 1739 insertions, 0 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c new file mode 100644 index 00000000000..13c14cb6dee --- /dev/null +++ b/net/ipv4/tcp_output.c @@ -0,0 +1,1739 @@ +/* + * 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_output.c,v 1.146 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 : Retransmit queue handled by TCP. + * : Fragmentation on mtu decrease + * : Segment collapse on retransmit + * : AF independence + * + * Linus Torvalds : send_delayed_ack + * David S. Miller : Charge memory using the right skb + * during syn/ack processing. + * David S. Miller : Output engine completely rewritten. + * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. + * Cacophonix Gaul : draft-minshall-nagle-01 + * J Hadi Salim : ECN support + * + */ + +#include <net/tcp.h> + +#include <linux/compiler.h> +#include <linux/module.h> +#include <linux/smp_lock.h> + +/* People can turn this off for buggy TCP's found in printers etc. */ +int sysctl_tcp_retrans_collapse = 1; + +/* This limits the percentage of the congestion window which we + * will allow a single TSO frame to consume. Building TSO frames + * which are too large can cause TCP streams to be bursty. + */ +int sysctl_tcp_tso_win_divisor = 8; + +static inline void update_send_head(struct sock *sk, struct tcp_sock *tp, + struct sk_buff *skb) +{ + sk->sk_send_head = skb->next; + if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue) + sk->sk_send_head = NULL; + tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; + tcp_packets_out_inc(sk, tp, skb); +} + +/* SND.NXT, if window was not shrunk. + * If window has been shrunk, what should we make? It is not clear at all. + * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( + * Anything in between SND.UNA...SND.UNA+SND.WND also can be already + * invalid. OK, let's make this for now: + */ +static inline __u32 tcp_acceptable_seq(struct sock *sk, struct tcp_sock *tp) +{ + if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt)) + return tp->snd_nxt; + else + return tp->snd_una+tp->snd_wnd; +} + +/* Calculate mss to advertise in SYN segment. + * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: + * + * 1. It is independent of path mtu. + * 2. Ideally, it is maximal possible segment size i.e. 65535-40. + * 3. For IPv4 it is reasonable to calculate it from maximal MTU of + * attached devices, because some buggy hosts are confused by + * large MSS. + * 4. We do not make 3, we advertise MSS, calculated from first + * hop device mtu, but allow to raise it to ip_rt_min_advmss. + * This may be overridden via information stored in routing table. + * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, + * probably even Jumbo". + */ +static __u16 tcp_advertise_mss(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + int mss = tp->advmss; + + if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { + mss = dst_metric(dst, RTAX_ADVMSS); + tp->advmss = mss; + } + + return (__u16)mss; +} + +/* RFC2861. Reset CWND after idle period longer RTO to "restart window". + * This is the first part of cwnd validation mechanism. */ +static void tcp_cwnd_restart(struct tcp_sock *tp, struct dst_entry *dst) +{ + s32 delta = tcp_time_stamp - tp->lsndtime; + u32 restart_cwnd = tcp_init_cwnd(tp, dst); + u32 cwnd = tp->snd_cwnd; + + if (tcp_is_vegas(tp)) + tcp_vegas_enable(tp); + + tp->snd_ssthresh = tcp_current_ssthresh(tp); + restart_cwnd = min(restart_cwnd, cwnd); + + while ((delta -= tp->rto) > 0 && cwnd > restart_cwnd) + cwnd >>= 1; + tp->snd_cwnd = max(cwnd, restart_cwnd); + tp->snd_cwnd_stamp = tcp_time_stamp; + tp->snd_cwnd_used = 0; +} + +static inline void tcp_event_data_sent(struct tcp_sock *tp, + struct sk_buff *skb, struct sock *sk) +{ + u32 now = tcp_time_stamp; + + if (!tp->packets_out && (s32)(now - tp->lsndtime) > tp->rto) + tcp_cwnd_restart(tp, __sk_dst_get(sk)); + + tp->lsndtime = now; + + /* If it is a reply for ato after last received + * packet, enter pingpong mode. + */ + if ((u32)(now - tp->ack.lrcvtime) < tp->ack.ato) + tp->ack.pingpong = 1; +} + +static __inline__ void tcp_event_ack_sent(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tcp_dec_quickack_mode(tp); + tcp_clear_xmit_timer(sk, TCP_TIME_DACK); +} + +/* Determine a window scaling and initial window to offer. + * Based on the assumption that the given amount of space + * will be offered. Store the results in the tp structure. + * NOTE: for smooth operation initial space offering should + * be a multiple of mss if possible. We assume here that mss >= 1. + * This MUST be enforced by all callers. + */ +void tcp_select_initial_window(int __space, __u32 mss, + __u32 *rcv_wnd, __u32 *window_clamp, + int wscale_ok, __u8 *rcv_wscale) +{ + unsigned int space = (__space < 0 ? 0 : __space); + + /* If no clamp set the clamp to the max possible scaled window */ + if (*window_clamp == 0) + (*window_clamp) = (65535 << 14); + space = min(*window_clamp, space); + + /* Quantize space offering to a multiple of mss if possible. */ + if (space > mss) + space = (space / mss) * mss; + + /* NOTE: offering an initial window larger than 32767 + * will break some buggy TCP stacks. We try to be nice. + * If we are not window scaling, then this truncates + * our initial window offering to 32k. There should also + * be a sysctl option to stop being nice. + */ + (*rcv_wnd) = min(space, MAX_TCP_WINDOW); + (*rcv_wscale) = 0; + if (wscale_ok) { + /* Set window scaling on max possible window + * See RFC1323 for an explanation of the limit to 14 + */ + space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); + while (space > 65535 && (*rcv_wscale) < 14) { + space >>= 1; + (*rcv_wscale)++; + } + } + + /* Set initial window to value enough for senders, + * following RFC1414. Senders, not following this RFC, + * will be satisfied with 2. + */ + if (mss > (1<<*rcv_wscale)) { + int init_cwnd = 4; + if (mss > 1460*3) + init_cwnd = 2; + else if (mss > 1460) + init_cwnd = 3; + if (*rcv_wnd > init_cwnd*mss) + *rcv_wnd = init_cwnd*mss; + } + + /* Set the clamp no higher than max representable value */ + (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); +} + +/* Chose a new window to advertise, update state in tcp_sock for the + * socket, and return result with RFC1323 scaling applied. The return + * value can be stuffed directly into th->window for an outgoing + * frame. + */ +static __inline__ u16 tcp_select_window(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 cur_win = tcp_receive_window(tp); + u32 new_win = __tcp_select_window(sk); + + /* Never shrink the offered window */ + if(new_win < cur_win) { + /* Danger Will Robinson! + * Don't update rcv_wup/rcv_wnd here or else + * we will not be able to advertise a zero + * window in time. --DaveM + * + * Relax Will Robinson. + */ + new_win = cur_win; + } + tp->rcv_wnd = new_win; + tp->rcv_wup = tp->rcv_nxt; + + /* Make sure we do not exceed the maximum possible + * scaled window. + */ + if (!tp->rx_opt.rcv_wscale) + new_win = min(new_win, MAX_TCP_WINDOW); + else + new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); + + /* RFC1323 scaling applied */ + new_win >>= tp->rx_opt.rcv_wscale; + + /* If we advertise zero window, disable fast path. */ + if (new_win == 0) + tp->pred_flags = 0; + + return new_win; +} + + +/* This routine actually transmits TCP packets queued in by + * tcp_do_sendmsg(). This is used by both the initial + * transmission and possible later retransmissions. + * All SKB's seen here are completely headerless. It is our + * job to build the TCP header, and pass the packet down to + * IP so it can do the same plus pass the packet off to the + * device. + * + * We are working here with either a clone of the original + * SKB, or a fresh unique copy made by the retransmit engine. + */ +static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb) +{ + if (skb != NULL) { + struct inet_sock *inet = inet_sk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); + int tcp_header_size = tp->tcp_header_len; + struct tcphdr *th; + int sysctl_flags; + int err; + + BUG_ON(!tcp_skb_pcount(skb)); + +#define SYSCTL_FLAG_TSTAMPS 0x1 +#define SYSCTL_FLAG_WSCALE 0x2 +#define SYSCTL_FLAG_SACK 0x4 + + sysctl_flags = 0; + if (tcb->flags & TCPCB_FLAG_SYN) { + tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS; + if(sysctl_tcp_timestamps) { + tcp_header_size += TCPOLEN_TSTAMP_ALIGNED; + sysctl_flags |= SYSCTL_FLAG_TSTAMPS; + } + if(sysctl_tcp_window_scaling) { + tcp_header_size += TCPOLEN_WSCALE_ALIGNED; + sysctl_flags |= SYSCTL_FLAG_WSCALE; + } + if(sysctl_tcp_sack) { + sysctl_flags |= SYSCTL_FLAG_SACK; + if(!(sysctl_flags & SYSCTL_FLAG_TSTAMPS)) + tcp_header_size += TCPOLEN_SACKPERM_ALIGNED; + } + } else if (tp->rx_opt.eff_sacks) { + /* A SACK is 2 pad bytes, a 2 byte header, plus + * 2 32-bit sequence numbers for each SACK block. + */ + tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED + + (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); + } + + /* + * If the connection is idle and we are restarting, + * then we don't want to do any Vegas calculations + * until we get fresh RTT samples. So when we + * restart, we reset our Vegas state to a clean + * slate. After we get acks for this flight of + * packets, _then_ we can make Vegas calculations + * again. + */ + if (tcp_is_vegas(tp) && tcp_packets_in_flight(tp) == 0) + tcp_vegas_enable(tp); + + th = (struct tcphdr *) skb_push(skb, tcp_header_size); + skb->h.th = th; + skb_set_owner_w(skb, sk); + + /* Build TCP header and checksum it. */ + th->source = inet->sport; + th->dest = inet->dport; + th->seq = htonl(tcb->seq); + th->ack_seq = htonl(tp->rcv_nxt); + *(((__u16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | tcb->flags); + if (tcb->flags & TCPCB_FLAG_SYN) { + /* RFC1323: The window in SYN & SYN/ACK segments + * is never scaled. + */ + th->window = htons(tp->rcv_wnd); + } else { + th->window = htons(tcp_select_window(sk)); + } + th->check = 0; + th->urg_ptr = 0; + + if (tp->urg_mode && + between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF)) { + th->urg_ptr = htons(tp->snd_up-tcb->seq); + th->urg = 1; + } + + if (tcb->flags & TCPCB_FLAG_SYN) { + tcp_syn_build_options((__u32 *)(th + 1), + tcp_advertise_mss(sk), + (sysctl_flags & SYSCTL_FLAG_TSTAMPS), + (sysctl_flags & SYSCTL_FLAG_SACK), + (sysctl_flags & SYSCTL_FLAG_WSCALE), + tp->rx_opt.rcv_wscale, + tcb->when, + tp->rx_opt.ts_recent); + } else { + tcp_build_and_update_options((__u32 *)(th + 1), + tp, tcb->when); + + TCP_ECN_send(sk, tp, skb, tcp_header_size); + } + tp->af_specific->send_check(sk, th, skb->len, skb); + + if (tcb->flags & TCPCB_FLAG_ACK) + tcp_event_ack_sent(sk); + + if (skb->len != tcp_header_size) + tcp_event_data_sent(tp, skb, sk); + + TCP_INC_STATS(TCP_MIB_OUTSEGS); + + err = tp->af_specific->queue_xmit(skb, 0); + if (err <= 0) + return err; + + tcp_enter_cwr(tp); + + /* NET_XMIT_CN is special. It does not guarantee, + * that this packet is lost. It tells that device + * is about to start to drop packets or already + * drops some packets of the same priority and + * invokes us to send less aggressively. + */ + return err == NET_XMIT_CN ? 0 : err; + } + return -ENOBUFS; +#undef SYSCTL_FLAG_TSTAMPS +#undef SYSCTL_FLAG_WSCALE +#undef SYSCTL_FLAG_SACK +} + + +/* This routine just queue's the buffer + * + * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, + * otherwise socket can stall. + */ +static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Advance write_seq and place onto the write_queue. */ + tp->write_seq = TCP_SKB_CB(skb)->end_seq; + skb_header_release(skb); + __skb_queue_tail(&sk->sk_write_queue, skb); + sk_charge_skb(sk, skb); + + /* Queue it, remembering where we must start sending. */ + if (sk->sk_send_head == NULL) + sk->sk_send_head = skb; +} + +static inline void tcp_tso_set_push(struct sk_buff *skb) +{ + /* Force push to be on for any TSO frames to workaround + * problems with busted implementations like Mac OS-X that + * hold off socket receive wakeups until push is seen. + */ + if (tcp_skb_pcount(skb) > 1) + TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; +} + +/* Send _single_ skb sitting at the send head. This function requires + * true push pending frames to setup probe timer etc. + */ +void tcp_push_one(struct sock *sk, unsigned cur_mss) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = sk->sk_send_head; + + if (tcp_snd_test(tp, skb, cur_mss, TCP_NAGLE_PUSH)) { + /* Send it out now. */ + TCP_SKB_CB(skb)->when = tcp_time_stamp; + tcp_tso_set_push(skb); + if (!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation))) { + sk->sk_send_head = NULL; + tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; + tcp_packets_out_inc(sk, tp, skb); + return; + } + } +} + +void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_std) +{ + if (skb->len <= mss_std) { + /* Avoid the costly divide in the normal + * non-TSO case. + */ + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + } else { + unsigned int factor; + + factor = skb->len + (mss_std - 1); + factor /= mss_std; + skb_shinfo(skb)->tso_segs = factor; + skb_shinfo(skb)->tso_size = mss_std; + } +} + +/* Function to create two new TCP segments. Shrinks the given segment + * to the specified size and appends a new segment with the rest of the + * packet to the list. This won't be called frequently, I hope. + * Remember, these are still headerless SKBs at this point. + */ +static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + int nsize; + u16 flags; + + nsize = skb_headlen(skb) - len; + if (nsize < 0) + nsize = 0; + + if (skb_cloned(skb) && + skb_is_nonlinear(skb) && + pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) + return -ENOMEM; + + /* Get a new skb... force flag on. */ + buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); + if (buff == NULL) + return -ENOMEM; /* We'll just try again later. */ + sk_charge_skb(sk, buff); + + /* Correct the sequence numbers. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; + TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; + + /* PSH and FIN should only be set in the second packet. */ + flags = TCP_SKB_CB(skb)->flags; + TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); + TCP_SKB_CB(buff)->flags = flags; + TCP_SKB_CB(buff)->sacked = + (TCP_SKB_CB(skb)->sacked & + (TCPCB_LOST | TCPCB_EVER_RETRANS | TCPCB_AT_TAIL)); + TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL; + + if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) { + /* Copy and checksum data tail into the new buffer. */ + buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize), + nsize, 0); + + skb_trim(skb, len); + + skb->csum = csum_block_sub(skb->csum, buff->csum, len); + } else { + skb->ip_summed = CHECKSUM_HW; + skb_split(skb, buff, len); + } + + buff->ip_summed = skb->ip_summed; + + /* Looks stupid, but our code really uses when of + * skbs, which it never sent before. --ANK + */ + TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; + + if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) { + tp->lost_out -= tcp_skb_pcount(skb); + tp->left_out -= tcp_skb_pcount(skb); + } + + /* Fix up tso_factor for both original and new SKB. */ + tcp_set_skb_tso_segs(skb, tp->mss_cache_std); + tcp_set_skb_tso_segs(buff, tp->mss_cache_std); + + if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) { + tp->lost_out += tcp_skb_pcount(skb); + tp->left_out += tcp_skb_pcount(skb); + } + + if (TCP_SKB_CB(buff)->sacked&TCPCB_LOST) { + tp->lost_out += tcp_skb_pcount(buff); + tp->left_out += tcp_skb_pcount(buff); + } + + /* Link BUFF into the send queue. */ + __skb_append(skb, buff); + + return 0; +} + +/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c + * eventually). The difference is that pulled data not copied, but + * immediately discarded. + */ +static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len) +{ + int i, k, eat; + + eat = len; + k = 0; + for (i=0; i<skb_shinfo(skb)->nr_frags; i++) { + if (skb_shinfo(skb)->frags[i].size <= eat) { + put_page(skb_shinfo(skb)->frags[i].page); + eat -= skb_shinfo(skb)->frags[i].size; + } else { + skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; + if (eat) { + skb_shinfo(skb)->frags[k].page_offset += eat; + skb_shinfo(skb)->frags[k].size -= eat; + eat = 0; + } + k++; + } + } + skb_shinfo(skb)->nr_frags = k; + + skb->tail = skb->data; + skb->data_len -= len; + skb->len = skb->data_len; + return skb->tail; +} + +int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) +{ + if (skb_cloned(skb) && + pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) + return -ENOMEM; + + if (len <= skb_headlen(skb)) { + __skb_pull(skb, len); + } else { + if (__pskb_trim_head(skb, len-skb_headlen(skb)) == NULL) + return -ENOMEM; + } + + TCP_SKB_CB(skb)->seq += len; + skb->ip_summed = CHECKSUM_HW; + + skb->truesize -= len; + sk->sk_wmem_queued -= len; + sk->sk_forward_alloc += len; + sock_set_flag(sk, SOCK_QUEUE_SHRUNK); + + /* Any change of skb->len requires recalculation of tso + * factor and mss. + */ + if (tcp_skb_pcount(skb) > 1) + tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb)); + + return 0; +} + +/* This function synchronize snd mss to current pmtu/exthdr set. + + tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts + for TCP options, but includes only bare TCP header. + + tp->rx_opt.mss_clamp is mss negotiated at connection setup. + It is minumum of user_mss and mss received with SYN. + It also does not include TCP options. + + tp->pmtu_cookie is last pmtu, seen by this function. + + tp->mss_cache is current effective sending mss, including + all tcp options except for SACKs. It is evaluated, + taking into account current pmtu, but never exceeds + tp->rx_opt.mss_clamp. + + NOTE1. rfc1122 clearly states that advertised MSS + DOES NOT include either tcp or ip options. + + NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside + this function. --ANK (980731) + */ + +unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) +{ + struct tcp_sock *tp = tcp_sk(sk); + int mss_now; + + /* Calculate base mss without TCP options: + It is MMS_S - sizeof(tcphdr) of rfc1122 + */ + mss_now = pmtu - tp->af_specific->net_header_len - sizeof(struct tcphdr); + + /* Clamp it (mss_clamp does not include tcp options) */ + if (mss_now > tp->rx_opt.mss_clamp) + mss_now = tp->rx_opt.mss_clamp; + + /* Now subtract optional transport overhead */ + mss_now -= tp->ext_header_len; + + /* Then reserve room for full set of TCP options and 8 bytes of data */ + if (mss_now < 48) + mss_now = 48; + + /* Now subtract TCP options size, not including SACKs */ + mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); + + /* Bound mss with half of window */ + if (tp->max_window && mss_now > (tp->max_window>>1)) + mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len); + + /* And store cached results */ + tp->pmtu_cookie = pmtu; + tp->mss_cache = tp->mss_cache_std = mss_now; + + return mss_now; +} + +/* Compute the current effective MSS, taking SACKs and IP options, + * and even PMTU discovery events into account. + * + * LARGESEND note: !urg_mode is overkill, only frames up to snd_up + * cannot be large. However, taking into account rare use of URG, this + * is not a big flaw. + */ + +unsigned int tcp_current_mss(struct sock *sk, int large) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + unsigned int do_large, mss_now; + + mss_now = tp->mss_cache_std; + if (dst) { + u32 mtu = dst_mtu(dst); + if (mtu != tp->pmtu_cookie) + mss_now = tcp_sync_mss(sk, mtu); + } + + do_large = (large && + (sk->sk_route_caps & NETIF_F_TSO) && + !tp->urg_mode); + + if (do_large) { + unsigned int large_mss, factor, limit; + + large_mss = 65535 - tp->af_specific->net_header_len - + tp->ext_header_len - tp->tcp_header_len; + + if (tp->max_window && large_mss > (tp->max_window>>1)) + large_mss = max((tp->max_window>>1), + 68U - tp->tcp_header_len); + + factor = large_mss / mss_now; + + /* Always keep large mss multiple of real mss, but + * do not exceed 1/tso_win_divisor of the congestion window + * so we can keep the ACK clock ticking and minimize + * bursting. + */ + limit = tp->snd_cwnd; + if (sysctl_tcp_tso_win_divisor) + limit /= sysctl_tcp_tso_win_divisor; + limit = max(1U, limit); + if (factor > limit) + factor = limit; + + tp->mss_cache = mss_now * factor; + + mss_now = tp->mss_cache; + } + + if (tp->rx_opt.eff_sacks) + mss_now -= (TCPOLEN_SACK_BASE_ALIGNED + + (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); + return mss_now; +} + +/* This routine writes packets to the network. It advances the + * send_head. This happens as incoming acks open up the remote + * window for us. + * + * Returns 1, if no segments are in flight and we have queued segments, but + * cannot send anything now because of SWS or another problem. + */ +int tcp_write_xmit(struct sock *sk, int nonagle) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int mss_now; + + /* If we are closed, the bytes will have to remain here. + * In time closedown will finish, we empty the write queue and all + * will be happy. + */ + if (sk->sk_state != TCP_CLOSE) { + struct sk_buff *skb; + int sent_pkts = 0; + + /* Account for SACKS, we may need to fragment due to this. + * It is just like the real MSS changing on us midstream. + * We also handle things correctly when the user adds some + * IP options mid-stream. Silly to do, but cover it. + */ + mss_now = tcp_current_mss(sk, 1); + + while ((skb = sk->sk_send_head) && + tcp_snd_test(tp, skb, mss_now, + tcp_skb_is_last(sk, skb) ? nonagle : + TCP_NAGLE_PUSH)) { + if (skb->len > mss_now) { + if (tcp_fragment(sk, skb, mss_now)) + break; + } + + TCP_SKB_CB(skb)->when = tcp_time_stamp; + tcp_tso_set_push(skb); + if (tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC))) + break; + + /* Advance the send_head. This one is sent out. + * This call will increment packets_out. + */ + update_send_head(sk, tp, skb); + + tcp_minshall_update(tp, mss_now, skb); + sent_pkts = 1; + } + + if (sent_pkts) { + tcp_cwnd_validate(sk, tp); + return 0; + } + + return !tp->packets_out && sk->sk_send_head; + } + return 0; +} + +/* This function returns the amount that we can raise the + * usable window based on the following constraints + * + * 1. The window can never be shrunk once it is offered (RFC 793) + * 2. We limit memory per socket + * + * RFC 1122: + * "the suggested [SWS] avoidance algorithm for the receiver is to keep + * RECV.NEXT + RCV.WIN fixed until: + * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" + * + * i.e. don't raise the right edge of the window until you can raise + * it at least MSS bytes. + * + * Unfortunately, the recommended algorithm breaks header prediction, + * since header prediction assumes th->window stays fixed. + * + * Strictly speaking, keeping th->window fixed violates the receiver + * side SWS prevention criteria. The problem is that under this rule + * a stream of single byte packets will cause the right side of the + * window to always advance by a single byte. + * + * Of course, if the sender implements sender side SWS prevention + * then this will not be a problem. + * + * BSD seems to make the following compromise: + * + * If the free space is less than the 1/4 of the maximum + * space available and the free space is less than 1/2 mss, + * then set the window to 0. + * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] + * Otherwise, just prevent the window from shrinking + * and from being larger than the largest representable value. + * + * This prevents incremental opening of the window in the regime + * where TCP is limited by the speed of the reader side taking + * data out of the TCP receive queue. It does nothing about + * those cases where the window is constrained on the sender side + * because the pipeline is full. + * + * BSD also seems to "accidentally" limit itself to windows that are a + * multiple of MSS, at least until the free space gets quite small. + * This would appear to be a side effect of the mbuf implementation. + * Combining these two algorithms results in the observed behavior + * of having a fixed window size at almost all times. + * + * Below we obtain similar behavior by forcing the offered window to + * a multiple of the mss when it is feasible to do so. + * + * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. + * Regular options like TIMESTAMP are taken into account. + */ +u32 __tcp_select_window(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + /* MSS for the peer's data. Previous verions used mss_clamp + * here. I don't know if the value based on our guesses + * of peer's MSS is better for the performance. It's more correct + * but may be worse for the performance because of rcv_mss + * fluctuations. --SAW 1998/11/1 + */ + int mss = tp->ack.rcv_mss; + int free_space = tcp_space(sk); + int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); + int window; + + if (mss > full_space) + mss = full_space; + + if (free_space < full_space/2) { + tp->ack.quick = 0; + + if (tcp_memory_pressure) + tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss); + + if (free_space < mss) + return 0; + } + + if (free_space > tp->rcv_ssthresh) + free_space = tp->rcv_ssthresh; + + /* Don't do rounding if we are using window scaling, since the + * scaled window will not line up with the MSS boundary anyway. + */ + window = tp->rcv_wnd; + if (tp->rx_opt.rcv_wscale) { + window = free_space; + + /* Advertise enough space so that it won't get scaled away. + * Import case: prevent zero window announcement if + * 1<<rcv_wscale > mss. + */ + if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) + window = (((window >> tp->rx_opt.rcv_wscale) + 1) + << tp->rx_opt.rcv_wscale); + } else { + /* Get the largest window that is a nice multiple of mss. + * Window clamp already applied above. + * If our current window offering is within 1 mss of the + * free space we just keep it. This prevents the divide + * and multiply from happening most of the time. + * We also don't do any window rounding when the free space + * is too small. + */ + if (window <= free_space - mss || window > free_space) + window = (free_space/mss)*mss; + } + + return window; +} + +/* Attempt to collapse two adjacent SKB's during retransmission. */ +static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *next_skb = skb->next; + + /* The first test we must make is that neither of these two + * SKB's are still referenced by someone else. + */ + if (!skb_cloned(skb) && !skb_cloned(next_skb)) { + int skb_size = skb->len, next_skb_size = next_skb->len; + u16 flags = TCP_SKB_CB(skb)->flags; + + /* Also punt if next skb has been SACK'd. */ + if(TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) + return; + + /* Next skb is out of window. */ + if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd)) + return; + + /* Punt if not enough space exists in the first SKB for + * the data in the second, or the total combined payload + * would exceed the MSS. + */ + if ((next_skb_size > skb_tailroom(skb)) || + ((skb_size + next_skb_size) > mss_now)) + return; + + BUG_ON(tcp_skb_pcount(skb) != 1 || + tcp_skb_pcount(next_skb) != 1); + + /* Ok. We will be able to collapse the packet. */ + __skb_unlink(next_skb, next_skb->list); + + memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size); + + if (next_skb->ip_summed == CHECKSUM_HW) + skb->ip_summed = CHECKSUM_HW; + + if (skb->ip_summed != CHECKSUM_HW) + skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); + + /* Update sequence range on original skb. */ + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; + + /* Merge over control information. */ + flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */ + TCP_SKB_CB(skb)->flags = flags; + + /* All done, get rid of second SKB and account for it so + * packet counting does not break. + */ + TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL); + if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS) + tp->retrans_out -= tcp_skb_pcount(next_skb); + if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) { + tp->lost_out -= tcp_skb_pcount(next_skb); + tp->left_out -= tcp_skb_pcount(next_skb); + } + /* Reno case is special. Sigh... */ + if (!tp->rx_opt.sack_ok && tp->sacked_out) { + tcp_dec_pcount_approx(&tp->sacked_out, next_skb); + tp->left_out -= tcp_skb_pcount(next_skb); + } + + /* Not quite right: it can be > snd.fack, but + * it is better to underestimate fackets. + */ + tcp_dec_pcount_approx(&tp->fackets_out, next_skb); + tcp_packets_out_dec(tp, next_skb); + sk_stream_free_skb(sk, next_skb); + } +} + +/* Do a simple retransmit without using the backoff mechanisms in + * tcp_timer. This is used for path mtu discovery. + * The socket is already locked here. + */ +void tcp_simple_retransmit(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + unsigned int mss = tcp_current_mss(sk, 0); + int lost = 0; + + sk_stream_for_retrans_queue(skb, sk) { + if (skb->len > mss && + !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { + if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { + TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; + tp->retrans_out -= tcp_skb_pcount(skb); + } + if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) { + TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; + tp->lost_out += tcp_skb_pcount(skb); + lost = 1; + } + } + } + + if (!lost) + return; + + tcp_sync_left_out(tp); + + /* Don't muck with the congestion window here. + * Reason is that we do not increase amount of _data_ + * in network, but units changed and effective + * cwnd/ssthresh really reduced now. + */ + if (tp->ca_state != TCP_CA_Loss) { + tp->high_seq = tp->snd_nxt; + tp->snd_ssthresh = tcp_current_ssthresh(tp); + tp->prior_ssthresh = 0; + tp->undo_marker = 0; + tcp_set_ca_state(tp, TCP_CA_Loss); + } + tcp_xmit_retransmit_queue(sk); +} + +/* This retransmits one SKB. Policy decisions and retransmit queue + * state updates are done by the caller. Returns non-zero if an + * error occurred which prevented the send. + */ +int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int cur_mss = tcp_current_mss(sk, 0); + int err; + + /* Do not sent more than we queued. 1/4 is reserved for possible + * copying overhead: frgagmentation, tunneling, mangling etc. + */ + if (atomic_read(&sk->sk_wmem_alloc) > + min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) + return -EAGAIN; + + if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { + if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) + BUG(); + + 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 (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) + return -ENOMEM; + } + + /* If receiver has shrunk his window, and skb is out of + * new window, do not retransmit it. The exception is the + * case, when window is shrunk to zero. In this case + * our retransmit serves as a zero window probe. + */ + if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd) + && TCP_SKB_CB(skb)->seq != tp->snd_una) + return -EAGAIN; + + if (skb->len > cur_mss) { + int old_factor = tcp_skb_pcount(skb); + int new_factor; + + if (tcp_fragment(sk, skb, cur_mss)) + return -ENOMEM; /* We'll try again later. */ + + /* New SKB created, account for it. */ + new_factor = tcp_skb_pcount(skb); + tp->packets_out -= old_factor - new_factor; + tp->packets_out += tcp_skb_pcount(skb->next); + } + + /* Collapse two adjacent packets if worthwhile and we can. */ + if(!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && + (skb->len < (cur_mss >> 1)) && + (skb->next != sk->sk_send_head) && + (skb->next != (struct sk_buff *)&sk->sk_write_queue) && + (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) && + (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) && + (sysctl_tcp_retrans_collapse != 0)) + tcp_retrans_try_collapse(sk, skb, cur_mss); + + if(tp->af_specific->rebuild_header(sk)) + return -EHOSTUNREACH; /* Routing failure or similar. */ + + /* Some Solaris stacks overoptimize and ignore the FIN on a + * retransmit when old data is attached. So strip it off + * since it is cheap to do so and saves bytes on the network. + */ + if(skb->len > 0 && + (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && + tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { + if (!pskb_trim(skb, 0)) { + TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1; + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + skb->ip_summed = CHECKSUM_NONE; + skb->csum = 0; + } + } + + /* Make a copy, if the first transmission SKB clone we made + * is still in somebody's hands, else make a clone. + */ + TCP_SKB_CB(skb)->when = tcp_time_stamp; + tcp_tso_set_push(skb); + + err = tcp_transmit_skb(sk, (skb_cloned(skb) ? + pskb_copy(skb, GFP_ATOMIC): + skb_clone(skb, GFP_ATOMIC))); + + if (err == 0) { + /* Update global TCP statistics. */ + TCP_INC_STATS(TCP_MIB_RETRANSSEGS); + + tp->total_retrans++; + +#if FASTRETRANS_DEBUG > 0 + if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { + if (net_ratelimit()) + printk(KERN_DEBUG "retrans_out leaked.\n"); + } +#endif + TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; + tp->retrans_out += tcp_skb_pcount(skb); + + /* Save stamp of the first retransmit. */ + if (!tp->retrans_stamp) + tp->retrans_stamp = TCP_SKB_CB(skb)->when; + + tp->undo_retrans++; + + /* snd_nxt is stored to detect loss of retransmitted segment, + * see tcp_input.c tcp_sacktag_write_queue(). + */ + TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; + } + return err; +} + +/* This gets called after a retransmit timeout, and the initially + * retransmitted data is acknowledged. It tries to continue + * resending the rest of the retransmit queue, until either + * we've sent it all or the congestion window limit is reached. + * If doing SACK, the first ACK which comes back for a timeout + * based retransmit packet might feed us FACK information again. + * If so, we use it to avoid unnecessarily retransmissions. + */ +void tcp_xmit_retransmit_queue(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + int packet_cnt = tp->lost_out; + + /* First pass: retransmit lost packets. */ + if (packet_cnt) { + sk_stream_for_retrans_queue(skb, sk) { + __u8 sacked = TCP_SKB_CB(skb)->sacked; + + /* Assume this retransmit will generate + * only one packet for congestion window + * calculation purposes. This works because + * tcp_retransmit_skb() will chop up the + * packet to be MSS sized and all the + * packet counting works out. + */ + if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) + return; + + if (sacked&TCPCB_LOST) { + if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) { + if (tcp_retransmit_skb(sk, skb)) + return; + if (tp->ca_state != TCP_CA_Loss) + NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS); + else + NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS); + + if (skb == + skb_peek(&sk->sk_write_queue)) + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + } + + packet_cnt -= tcp_skb_pcount(skb); + if (packet_cnt <= 0) + break; + } + } + } + + /* OK, demanded retransmission is finished. */ + + /* Forward retransmissions are possible only during Recovery. */ + if (tp->ca_state != TCP_CA_Recovery) + return; + + /* No forward retransmissions in Reno are possible. */ + if (!tp->rx_opt.sack_ok) + return; + + /* Yeah, we have to make difficult choice between forward transmission + * and retransmission... Both ways have their merits... + * + * For now we do not retransmit anything, while we have some new + * segments to send. + */ + + if (tcp_may_send_now(sk, tp)) + return; + + packet_cnt = 0; + + sk_stream_for_retrans_queue(skb, sk) { + /* Similar to the retransmit loop above we + * can pretend that the retransmitted SKB + * we send out here will be composed of one + * real MSS sized packet because tcp_retransmit_skb() + * will fragment it if necessary. + */ + if (++packet_cnt > tp->fackets_out) + break; + + if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) + break; + + if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) + continue; + + /* Ok, retransmit it. */ + if (tcp_retransmit_skb(sk, skb)) + break; + + if (skb == skb_peek(&sk->sk_write_queue)) + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + + NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS); + } +} + + +/* Send a fin. The caller locks the socket for us. This cannot be + * allowed to fail queueing a FIN frame under any circumstances. + */ +void tcp_send_fin(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue); + int mss_now; + + /* Optimization, tack on the FIN if we have a queue of + * unsent frames. But be careful about outgoing SACKS + * and IP options. + */ + mss_now = tcp_current_mss(sk, 1); + + if (sk->sk_send_head != NULL) { + TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; + TCP_SKB_CB(skb)->end_seq++; + tp->write_seq++; + } else { + /* Socket is locked, keep trying until memory is available. */ + for (;;) { + skb = alloc_skb(MAX_TCP_HEADER, GFP_KERNEL); + if (skb) + break; + yield(); + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + skb->csum = 0; + TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); + TCP_SKB_CB(skb)->sacked = 0; + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + + /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ + TCP_SKB_CB(skb)->seq = tp->write_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; + tcp_queue_skb(sk, skb); + } + __tcp_push_pending_frames(sk, tp, mss_now, TCP_NAGLE_OFF); +} + +/* We get here when a process closes a file descriptor (either due to + * an explicit close() or as a byproduct of exit()'ing) and there + * was unread data in the receive queue. This behavior is recommended + * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM + */ +void tcp_send_active_reset(struct sock *sk, int priority) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + /* NOTE: No TCP options attached and we never retransmit this. */ + skb = alloc_skb(MAX_TCP_HEADER, priority); + if (!skb) { + NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + skb->csum = 0; + TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST); + TCP_SKB_CB(skb)->sacked = 0; + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + + /* Send it off. */ + TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp); + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; + TCP_SKB_CB(skb)->when = tcp_time_stamp; + if (tcp_transmit_skb(sk, skb)) + NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); +} + +/* WARNING: This routine must only be called when we have already sent + * a SYN packet that crossed the incoming SYN that caused this routine + * to get called. If this assumption fails then the initial rcv_wnd + * and rcv_wscale values will not be correct. + */ +int tcp_send_synack(struct sock *sk) +{ + struct sk_buff* skb; + + skb = skb_peek(&sk->sk_write_queue); + if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) { + printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); + return -EFAULT; + } + if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) { + if (skb_cloned(skb)) { + struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); + if (nskb == NULL) + return -ENOMEM; + __skb_unlink(skb, &sk->sk_write_queue); + skb_header_release(nskb); + __skb_queue_head(&sk->sk_write_queue, nskb); + sk_stream_free_skb(sk, skb); + sk_charge_skb(sk, nskb); + skb = nskb; + } + + TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; + TCP_ECN_send_synack(tcp_sk(sk), skb); + } + TCP_SKB_CB(skb)->when = tcp_time_stamp; + return tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)); +} + +/* + * Prepare a SYN-ACK. + */ +struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst, + struct open_request *req) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcphdr *th; + int tcp_header_size; + struct sk_buff *skb; + + skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC); + if (skb == NULL) + return NULL; + + /* Reserve space for headers. */ + skb_reserve(skb, MAX_TCP_HEADER); + + skb->dst = dst_clone(dst); + + tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS + + (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) + + (req->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) + + /* SACK_PERM is in the place of NOP NOP of TS */ + ((req->sack_ok && !req->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0)); + skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size); + + memset(th, 0, sizeof(struct tcphdr)); + th->syn = 1; + th->ack = 1; + if (dst->dev->features&NETIF_F_TSO) + req->ecn_ok = 0; + TCP_ECN_make_synack(req, th); + th->source = inet_sk(sk)->sport; + th->dest = req->rmt_port; + TCP_SKB_CB(skb)->seq = req->snt_isn; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; + TCP_SKB_CB(skb)->sacked = 0; + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + th->seq = htonl(TCP_SKB_CB(skb)->seq); + th->ack_seq = htonl(req->rcv_isn + 1); + if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ + __u8 rcv_wscale; + /* Set this up on the first call only */ + req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); + /* tcp_full_space because it is guaranteed to be the first packet */ + tcp_select_initial_window(tcp_full_space(sk), + dst_metric(dst, RTAX_ADVMSS) - (req->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), + &req->rcv_wnd, + &req->window_clamp, + req->wscale_ok, + &rcv_wscale); + req->rcv_wscale = rcv_wscale; + } + + /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ + th->window = htons(req->rcv_wnd); + + TCP_SKB_CB(skb)->when = tcp_time_stamp; + tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), req->tstamp_ok, + req->sack_ok, req->wscale_ok, req->rcv_wscale, + TCP_SKB_CB(skb)->when, + req->ts_recent); + + skb->csum = 0; + th->doff = (tcp_header_size >> 2); + TCP_INC_STATS(TCP_MIB_OUTSEGS); + return skb; +} + +/* + * Do all connect socket setups that can be done AF independent. + */ +static inline void tcp_connect_init(struct sock *sk) +{ + struct dst_entry *dst = __sk_dst_get(sk); + struct tcp_sock *tp = tcp_sk(sk); + __u8 rcv_wscale; + + /* We'll fix this up when we get a response from the other end. + * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. + */ + tp->tcp_header_len = sizeof(struct tcphdr) + + (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); + + /* If user gave his TCP_MAXSEG, record it to clamp */ + if (tp->rx_opt.user_mss) + tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; + tp->max_window = 0; + tcp_sync_mss(sk, dst_mtu(dst)); + + if (!tp->window_clamp) + tp->window_clamp = dst_metric(dst, RTAX_WINDOW); + tp->advmss = dst_metric(dst, RTAX_ADVMSS); + tcp_initialize_rcv_mss(sk); + tcp_ca_init(tp); + + tcp_select_initial_window(tcp_full_space(sk), + tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), + &tp->rcv_wnd, + &tp->window_clamp, + sysctl_tcp_window_scaling, + &rcv_wscale); + + tp->rx_opt.rcv_wscale = rcv_wscale; + tp->rcv_ssthresh = tp->rcv_wnd; + + sk->sk_err = 0; + sock_reset_flag(sk, SOCK_DONE); + tp->snd_wnd = 0; + tcp_init_wl(tp, tp->write_seq, 0); + tp->snd_una = tp->write_seq; + tp->snd_sml = tp->write_seq; + tp->rcv_nxt = 0; + tp->rcv_wup = 0; + tp->copied_seq = 0; + + tp->rto = TCP_TIMEOUT_INIT; + tp->retransmits = 0; + tcp_clear_retrans(tp); +} + +/* + * Build a SYN and send it off. + */ +int tcp_connect(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + + tcp_connect_init(sk); + + buff = alloc_skb(MAX_TCP_HEADER + 15, sk->sk_allocation); + if (unlikely(buff == NULL)) + return -ENOBUFS; + + /* Reserve space for headers. */ + skb_reserve(buff, MAX_TCP_HEADER); + + TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN; + TCP_ECN_send_syn(sk, tp, buff); + TCP_SKB_CB(buff)->sacked = 0; + skb_shinfo(buff)->tso_segs = 1; + skb_shinfo(buff)->tso_size = 0; + buff->csum = 0; + TCP_SKB_CB(buff)->seq = tp->write_seq++; + TCP_SKB_CB(buff)->end_seq = tp->write_seq; + tp->snd_nxt = tp->write_seq; + tp->pushed_seq = tp->write_seq; + tcp_ca_init(tp); + + /* Send it off. */ + TCP_SKB_CB(buff)->when = tcp_time_stamp; + tp->retrans_stamp = TCP_SKB_CB(buff)->when; + skb_header_release(buff); + __skb_queue_tail(&sk->sk_write_queue, buff); + sk_charge_skb(sk, buff); + tp->packets_out += tcp_skb_pcount(buff); + tcp_transmit_skb(sk, skb_clone(buff, GFP_KERNEL)); + TCP_INC_STATS(TCP_MIB_ACTIVEOPENS); + + /* Timer for repeating the SYN until an answer. */ + tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); + return 0; +} + +/* Send out a delayed ack, the caller does the policy checking + * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() + * for details. + */ +void tcp_send_delayed_ack(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int ato = tp->ack.ato; + unsigned long timeout; + + if (ato > TCP_DELACK_MIN) { + int max_ato = HZ/2; + + if (tp->ack.pingpong || (tp->ack.pending&TCP_ACK_PUSHED)) + max_ato = TCP_DELACK_MAX; + + /* Slow path, intersegment interval is "high". */ + + /* If some rtt estimate is known, use it to bound delayed ack. + * Do not use tp->rto here, use results of rtt measurements + * directly. + */ + if (tp->srtt) { + int rtt = max(tp->srtt>>3, TCP_DELACK_MIN); + + if (rtt < max_ato) + max_ato = rtt; + } + + ato = min(ato, max_ato); + } + + /* Stay within the limit we were given */ + timeout = jiffies + ato; + + /* Use new timeout only if there wasn't a older one earlier. */ + if (tp->ack.pending&TCP_ACK_TIMER) { + /* If delack timer was blocked or is about to expire, + * send ACK now. + */ + if (tp->ack.blocked || time_before_eq(tp->ack.timeout, jiffies+(ato>>2))) { + tcp_send_ack(sk); + return; + } + + if (!time_before(timeout, tp->ack.timeout)) + timeout = tp->ack.timeout; + } + tp->ack.pending |= TCP_ACK_SCHED|TCP_ACK_TIMER; + tp->ack.timeout = timeout; + sk_reset_timer(sk, &tp->delack_timer, timeout); +} + +/* This routine sends an ack and also updates the window. */ +void tcp_send_ack(struct sock *sk) +{ + /* If we have been reset, we may not send again. */ + if (sk->sk_state != TCP_CLOSE) { + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + + /* We are not putting this on the write queue, so + * tcp_transmit_skb() will set the ownership to this + * sock. + */ + buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); + if (buff == NULL) { + tcp_schedule_ack(tp); + tp->ack.ato = TCP_ATO_MIN; + tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(buff, MAX_TCP_HEADER); + buff->csum = 0; + TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK; + TCP_SKB_CB(buff)->sacked = 0; + skb_shinfo(buff)->tso_segs = 1; + skb_shinfo(buff)->tso_size = 0; + + /* Send it off, this clears delayed acks for us. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp); + TCP_SKB_CB(buff)->when = tcp_time_stamp; + tcp_transmit_skb(sk, buff); + } +} + +/* This routine sends a packet with an out of date sequence + * number. It assumes the other end will try to ack it. + * + * Question: what should we make while urgent mode? + * 4.4BSD forces sending single byte of data. We cannot send + * out of window data, because we have SND.NXT==SND.MAX... + * + * Current solution: to send TWO zero-length segments in urgent mode: + * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is + * out-of-date with SND.UNA-1 to probe window. + */ +static int tcp_xmit_probe_skb(struct sock *sk, int urgent) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + /* We don't queue it, tcp_transmit_skb() sets ownership. */ + skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); + if (skb == NULL) + return -1; + + /* Reserve space for headers and set control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + skb->csum = 0; + TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK; + TCP_SKB_CB(skb)->sacked = urgent; + skb_shinfo(skb)->tso_segs = 1; + skb_shinfo(skb)->tso_size = 0; + + /* Use a previous sequence. This should cause the other + * end to send an ack. Don't queue or clone SKB, just + * send it. + */ + TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; + TCP_SKB_CB(skb)->when = tcp_time_stamp; + return tcp_transmit_skb(sk, skb); +} + +int tcp_write_wakeup(struct sock *sk) +{ + if (sk->sk_state != TCP_CLOSE) { + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + if ((skb = sk->sk_send_head) != NULL && + before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) { + int err; + unsigned int mss = tcp_current_mss(sk, 0); + unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq; + + if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) + tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; + + /* We are probing the opening of a window + * but the window size is != 0 + * must have been a result SWS avoidance ( sender ) + */ + if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || + skb->len > mss) { + seg_size = min(seg_size, mss); + TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; + if (tcp_fragment(sk, skb, seg_size)) + return -1; + /* SWS override triggered forced fragmentation. + * Disable TSO, the connection is too sick. */ + if (sk->sk_route_caps & NETIF_F_TSO) { + sock_set_flag(sk, SOCK_NO_LARGESEND); + sk->sk_route_caps &= ~NETIF_F_TSO; + tp->mss_cache = tp->mss_cache_std; + } + } else if (!tcp_skb_pcount(skb)) + tcp_set_skb_tso_segs(skb, tp->mss_cache_std); + + TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; + TCP_SKB_CB(skb)->when = tcp_time_stamp; + tcp_tso_set_push(skb); + err = tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)); + if (!err) { + update_send_head(sk, tp, skb); + } + return err; + } else { + if (tp->urg_mode && + between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF)) + tcp_xmit_probe_skb(sk, TCPCB_URG); + return tcp_xmit_probe_skb(sk, 0); + } + } + return -1; +} + +/* A window probe timeout has occurred. If window is not closed send + * a partial packet else a zero probe. + */ +void tcp_send_probe0(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + int err; + + err = tcp_write_wakeup(sk); + + if (tp->packets_out || !sk->sk_send_head) { + /* Cancel probe timer, if it is not required. */ + tp->probes_out = 0; + tp->backoff = 0; + return; + } + + if (err <= 0) { + if (tp->backoff < sysctl_tcp_retries2) + tp->backoff++; + tp->probes_out++; + tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, + min(tp->rto << tp->backoff, TCP_RTO_MAX)); + } else { + /* If packet was not sent due to local congestion, + * do not backoff and do not remember probes_out. + * Let local senders to fight for local resources. + * + * Use accumulated backoff yet. + */ + if (!tp->probes_out) + tp->probes_out=1; + tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, + min(tp->rto << tp->backoff, TCP_RESOURCE_PROBE_INTERVAL)); + } +} + +EXPORT_SYMBOL(tcp_connect); +EXPORT_SYMBOL(tcp_make_synack); +EXPORT_SYMBOL(tcp_simple_retransmit); +EXPORT_SYMBOL(tcp_sync_mss); |