diff options
| author | John Dykstra <john.dykstra1@gmail.com> | 2009-03-22 21:49:57 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-03-22 21:49:57 -0700 |
| commit | 96e0bf4b5193d0d97d139f99e2dd128763d55521 (patch) | |
| tree | 5e5a69c68072e605759a9cf9152caf0d0c6d1b7e | |
| parent | 763dccdc8e9775b247c3ea86ae8f5f592c12024e (diff) | |
tcp: Discard segments that ack data not yet sent
Discard incoming packets whose ack field iincludes data not yet sent.
This is consistent with RFC 793 Section 3.9.
Change tcp_ack() to distinguish between too-small and too-large ack
field values. Keep segments with too-large ack fields out of the fast
path, and change slow path to discard them.
Reported-by: Oliver Zheng <mailinglists+netdev@oliverzheng.com>
Signed-off-by: John Dykstra <john.dykstra1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/tcp_input.c | 27 |
1 files changed, 17 insertions, 10 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 8ac82b3703a..2bc8e27a163 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3585,15 +3585,18 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) int prior_packets; int frto_cwnd = 0; - /* If the ack is newer than sent or older than previous acks + /* If the ack is 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 the ack includes data we haven't sent yet, discard + * this segment (RFC793 Section 3.9). + */ + if (after(ack, tp->snd_nxt)) + goto invalid_ack; + if (after(ack, prior_snd_una)) flag |= FLAG_SND_UNA_ADVANCED; @@ -3683,6 +3686,10 @@ no_queue: tcp_ack_probe(sk); return 1; +invalid_ack: + SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); + return -1; + old_ack: if (TCP_SKB_CB(skb)->sacked) { tcp_sacktag_write_queue(sk, skb, prior_snd_una); @@ -3690,8 +3697,7 @@ old_ack: tcp_try_keep_open(sk); } -uninteresting_ack: - SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); + SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); return 0; } @@ -5141,7 +5147,8 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, */ if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && - TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { + TCP_SKB_CB(skb)->seq == tp->rcv_nxt && + !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { int tcp_header_len = tp->tcp_header_len; /* Timestamp header prediction: tcp_header_len @@ -5294,8 +5301,8 @@ slow_path: return -res; step5: - if (th->ack) - tcp_ack(sk, skb, FLAG_SLOWPATH); + if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) + goto discard; tcp_rcv_rtt_measure_ts(sk, skb); @@ -5632,7 +5639,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, /* step 5: check the ACK field */ if (th->ack) { - int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); + int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; switch (sk->sk_state) { case TCP_SYN_RECV: |