On Aug 8, 2023, at 20:49, Eric Dumazet [off-list ref] wrote:

On Tue, Aug 8, 2023 at 1:59 PM [off-list ref] wrote:

quoted

[……]

quoted

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index d45c96c7f5a4..f30d1467771c 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c

@@ -454,6 +454,18 @@ static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req)
                         req->timeout << req->num_timeout, TCP_RTO_MAX);

}

+static bool tcp_rtx_probe0_timed_out(struct sock *sk)

const struct sock *sk

quoted

+{
+       struct tcp_sock *tp = tcp_sk(sk);

const struct tcp_sock *tp = tcp_sk(sk);

quoted

+       u32 timeout_ts, rtx_ts, rcv_ts;
+
+       rtx_ts = tp->retrans_stamp;
+       rcv_ts = tp->rcv_tstamp;
+       timeout_ts = after(rtx_ts, rcv_ts) ? rtx_ts : rcv_ts;
+       timeout_ts += TCP_RTO_MAX;

If we are concerned with a socket dying too soon, I would suggest
adding 2*TCP_RTO_MAX instead of TCP_RTO_MAX

When a receiver is OOMing, it is possible the ACK RWIN 0 can not be sent all,
so tp->rcv_tstamp will not be refreshed. Or ACK could be lost in the
network path.

Yeah, I concern abort this too. I introduce the funtion “tcp_rtx_probe0_timed_out()”
here is to offer a more reliable way to check the timeout in the feature.
And for this time, we can fix the problem first, as you advised, adding
2*TCP_RTO_MAX instead of TCP_RTO_MAX.

This also suggests the net_dbg_ratelimited("Peer %pI4:%u/%u
unexpectedly shrunk window %u:%u (repaired)\n"...) messages
are slightly wrong, because they could be printed even if we did not
receive a new ACK packet from the remote peer.

Perhaps we should change them to include delays (how long @skb stayed
in rtx queue, how old is the last ACK we received)

Sounds great, which is more valuable. I’ll change them
in the next version.

Thanks!
Menglong Dong

quoted

+
+       return after(inet_csk(sk)->icsk_timeout, timeout_ts);
+}

/**
 *  tcp_retransmit_timer() - The TCP retransmit timeout handler

@@ -519,7 +531,7 @@ void tcp_retransmit_timer(struct sock *sk)
                                           tp->snd_una, tp->snd_nxt);
               }

#endif
-               if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) {
+               if (tcp_rtx_probe0_timed_out(sk)) {
                       tcp_write_err(sk);
                       goto out;
               }
--
2.40.1