diff options
| author | Yuchung Cheng <ycheng@google.com> | 2018-07-18 22:56:35 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-07-20 23:32:23 +0200 |
| commit | 27cde44a259c380a3c09066fc4b42de7dde9b1ad (patch) | |
| tree | 2f0249f49428f487fcda2249b5dab4d82dd8e514 /include | |
| parent | tcp: helpers to send special DCTCP ack (diff) | |
| download | linux-27cde44a259c380a3c09066fc4b42de7dde9b1ad.tar.xz linux-27cde44a259c380a3c09066fc4b42de7dde9b1ad.zip | |
tcp: do not cancel delay-AcK on DCTCP special ACK
Currently when a DCTCP receiver delays an ACK and receive a
data packet with a different CE mark from the previous one's, it
sends two immediate ACKs acking previous and latest sequences
respectly (for ECN accounting).
Previously sending the first ACK may mark off the delayed ACK timer
(tcp_event_ack_sent). This may subsequently prevent sending the
second ACK to acknowledge the latest sequence (tcp_ack_snd_check).
The culprit is that tcp_send_ack() assumes it always acknowleges
the latest sequence, which is not true for the first special ACK.
The fix is to not make the assumption in tcp_send_ack and check the
actual ack sequence before cancelling the delayed ACK. Further it's
safer to pass the ack sequence number as a local variable into
tcp_send_ack routine, instead of intercepting tp->rcv_nxt to avoid
future bugs like this.
Reported-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/tcp.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 3482d13d655b..a08de496d1b2 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -539,6 +539,7 @@ void tcp_send_fin(struct sock *sk); void tcp_send_active_reset(struct sock *sk, gfp_t priority); int tcp_send_synack(struct sock *); void tcp_push_one(struct sock *, unsigned int mss_now); +void __tcp_send_ack(struct sock *sk, u32 rcv_nxt); void tcp_send_ack(struct sock *sk); void tcp_send_delayed_ack(struct sock *sk); void tcp_send_loss_probe(struct sock *sk); |