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tcp: use signed arithmetic in tcp_rtx_probe0_timed_out()

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Due to timer wheel implementation, a timer will usually fire
after its schedule.

For instance, for HZ=1000, a timeout between 512ms and 4s
has a granularity of 64ms.
For this range of values, the extra delay could be up to 63ms.

For TCP, this means that tp->rcv_tstamp may be after
inet_csk(sk)->icsk_timeout whenever the timer interrupt
finally triggers, if one packet came during the extra delay.

We need to make sure tcp_rtx_probe0_timed_out() handles this case.

Fixes: e89688e3e9 ("net: tcp: fix unexcepted socket die when snd_wnd is 0")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Menglong Dong <imagedong@tencent.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/r/20240607125652.1472540-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2024-06-07 12:56:52 +00:00 committed by Jakub Kicinski
parent 70b3c88cec
commit 36534d3c54
1 changed files with 5 additions and 1 deletions
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6
net/ipv4/tcp_timer.c
View file

@ -485,8 +485,12 @@ static bool tcp_rtx_probe0_timed_out(const struct sock *sk,
{
const struct tcp_sock *tp = tcp_sk(sk);
const int timeout = TCP_RTO_MAX * 2;
u32 rcv_delta;
s32 rcv_delta;
/* Note: timer interrupt might have been delayed by at least one jiffy,
* and tp->rcv_tstamp might very well have been written recently.
* rcv_delta can thus be negative.
*/
rcv_delta = inet_csk(sk)->icsk_timeout - tp->rcv_tstamp;
if (rcv_delta <= timeout)
return false;