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authorJohn Dykstra <john.dykstra1@gmail.com>2009-03-22 21:49:57 -0700
committerDavid S. Miller <davem@davemloft.net>2009-03-22 21:49:57 -0700
commit96e0bf4b5193d0d97d139f99e2dd128763d55521 (patch)
tree5e5a69c68072e605759a9cf9152caf0d0c6d1b7e /net/ipv4/tcp_input.c
parent763dccdc8e9775b247c3ea86ae8f5f592c12024e (diff)
downloadblackbird-op-linux-96e0bf4b5193d0d97d139f99e2dd128763d55521.tar.gz
blackbird-op-linux-96e0bf4b5193d0d97d139f99e2dd128763d55521.zip
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>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c27
1 files changed, 17 insertions, 10 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 8ac82b3703ab..2bc8e27a163d 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:
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