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authorfuyuanli <fuyuanli@didiglobal.com>2023-05-31 16:01:50 +0800
committerPaolo Abeni <pabeni@redhat.com>2023-06-01 13:15:12 +0200
commit30c6f0bf9579debce27e45fac34fdc97e46acacc (patch)
tree50ea5008b9efe2d98f6768a7cc6a1c0178b5fb16 /net
parent4d56304e5827c8cc8cc18c75343d283af7c4825c (diff)
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tcp: fix mishandling when the sack compression is deferred.
In this patch, we mainly try to handle sending a compressed ack correctly if it's deferred. Here are more details in the old logic: When sack compression is triggered in the tcp_compressed_ack_kick(), if the sock is owned by user, it will set TCP_DELACK_TIMER_DEFERRED and then defer to the release cb phrase. Later once user releases the sock, tcp_delack_timer_handler() should send a ack as expected, which, however, cannot happen due to lack of ICSK_ACK_TIMER flag. Therefore, the receiver would not sent an ack until the sender's retransmission timeout. It definitely increases unnecessary latency. Fixes: 5d9f4262b7ea ("tcp: add SACK compression") Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: fuyuanli <fuyuanli@didiglobal.com> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com> Link: https://lore.kernel.org/netdev/20230529113804.GA20300@didi-ThinkCentre-M920t-N000/ Reviewed-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/20230531080150.GA20424@didi-ThinkCentre-M920t-N000 Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_input.c2
-rw-r--r--net/ipv4/tcp_timer.c16
2 files changed, 14 insertions, 4 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 61b6710f337a..bf8b22218dd4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4530,7 +4530,7 @@ static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
}
}
-static void tcp_sack_compress_send_ack(struct sock *sk)
+void tcp_sack_compress_send_ack(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index b839c2f91292..39eb947fe392 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -290,9 +290,19 @@ static int tcp_write_timeout(struct sock *sk)
void tcp_delack_timer_handler(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
- if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
- !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
+ if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
+ return;
+
+ /* Handling the sack compression case */
+ if (tp->compressed_ack) {
+ tcp_mstamp_refresh(tp);
+ tcp_sack_compress_send_ack(sk);
+ return;
+ }
+
+ if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
return;
if (time_after(icsk->icsk_ack.timeout, jiffies)) {
@@ -312,7 +322,7 @@ void tcp_delack_timer_handler(struct sock *sk)
inet_csk_exit_pingpong_mode(sk);
icsk->icsk_ack.ato = TCP_ATO_MIN;
}
- tcp_mstamp_refresh(tcp_sk(sk));
+ tcp_mstamp_refresh(tp);
tcp_send_ack(sk);
__NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS);
}