mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-01-23 16:53:58 -05:00
net: tcp: accept old ack during closing
For now, the packet with an old ack is not accepted if we are in FIN_WAIT1 state, which can cause retransmission. Taking the following case as an example: Client Server | | FIN_WAIT1(Send FIN, seq=10) FIN_WAIT1(Send FIN, seq=20, ack=10) | | | Send ACK(seq=21, ack=11) Recv ACK(seq=21, ack=11) | Recv FIN(seq=20, ack=10) In the case above, simultaneous close is happening, and the FIN and ACK packet that send from the server is out of order. Then, the FIN will be dropped by the client, as it has an old ack. Then, the server has to retransmit the FIN, which can cause delay if the server has set the SO_LINGER on the socket. Old ack is accepted in the ESTABLISHED and TIME_WAIT state, and I think it should be better to keep the same logic. In this commit, we accept old ack in FIN_WAIT1/FIN_WAIT2/CLOSING/LAST_ACK states. Maybe we should limit it to FIN_WAIT1 for now? Signed-off-by: Menglong Dong <menglong8.dong@gmail.com> Reviewed-by: Simon Horman <horms@kernel.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20240126040519.1846345-1-menglong8.dong@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
parent
67475eb989
commit
795a7dfbc3
1 changed files with 11 additions and 7 deletions
|
@ -6699,17 +6699,21 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
|
|||
return 0;
|
||||
|
||||
/* step 5: check the ACK field */
|
||||
acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
|
||||
FLAG_UPDATE_TS_RECENT |
|
||||
FLAG_NO_CHALLENGE_ACK) > 0;
|
||||
reason = tcp_ack(sk, skb, FLAG_SLOWPATH |
|
||||
FLAG_UPDATE_TS_RECENT |
|
||||
FLAG_NO_CHALLENGE_ACK);
|
||||
|
||||
if (!acceptable) {
|
||||
if ((int)reason <= 0) {
|
||||
if (sk->sk_state == TCP_SYN_RECV)
|
||||
return 1; /* send one RST */
|
||||
tcp_send_challenge_ack(sk);
|
||||
SKB_DR_SET(reason, TCP_OLD_ACK);
|
||||
goto discard;
|
||||
/* accept old ack during closing */
|
||||
if ((int)reason < 0) {
|
||||
tcp_send_challenge_ack(sk);
|
||||
reason = -reason;
|
||||
goto discard;
|
||||
}
|
||||
}
|
||||
SKB_DR_SET(reason, NOT_SPECIFIED);
|
||||
switch (sk->sk_state) {
|
||||
case TCP_SYN_RECV:
|
||||
tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */
|
||||
|
|
Loading…
Add table
Reference in a new issue