Messages in this thread | | | Subject | Re: [PATCH net-next v3 3/3] net: tcp: fix unexcepted socket die when snd_wnd is 0 | From | Menglong Dong <> | Date | Tue, 8 Aug 2023 21:07:40 +0800 |
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> On Aug 8, 2023, at 20:49, Eric Dumazet <edumazet@google.com> wrote: > > On Tue, Aug 8, 2023 at 1:59 PM <menglong8.dong@gmail.com> wrote: >> [……] >> >> 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 > >> +{ >> + struct tcp_sock *tp = tcp_sk(sk); > > const struct tcp_sock *tp = tcp_sk(sk); > >> + 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
>> + >> + 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
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