diff options
| author | Jason Xing <kernelxing@tencent.com> | 2023-08-11 10:37:47 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-08-15 20:24:04 +0100 |
| commit | e4dd0d3a2f64b8bd8029ec70f52bdbebd0644408 (patch) | |
| tree | 6cf24c26f399fdb42cb17c48d46b76bda20ec507 | |
| parent | 8a519a572598b7c0c07b02f69bf5b4e8dd4b2d7d (diff) | |
| download | nf-e4dd0d3a2f64b8bd8029ec70f52bdbebd0644408.tar.gz | |
net: fix the RTO timer retransmitting skb every 1ms if linear option is enabled
In the real workload, I encountered an issue which could cause the RTO
timer to retransmit the skb per 1ms with linear option enabled. The amount
of lost-retransmitted skbs can go up to 1000+ instantly.
The root cause is that if the icsk_rto happens to be zero in the 6th round
(which is the TCP_THIN_LINEAR_RETRIES value), then it will always be zero
due to the changed calculation method in tcp_retransmit_timer() as follows:
icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
Above line could be converted to
icsk->icsk_rto = min(0 << 1, TCP_RTO_MAX) = 0
Therefore, the timer expires so quickly without any doubt.
I read through the RFC 6298 and found that the RTO value can be rounded
up to a certain value, in Linux, say TCP_RTO_MIN as default, which is
regarded as the lower bound in this patch as suggested by Eric.
Fixes: 36e31b0af587 ("net: TCP thin linear timeouts")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/ipv4/tcp_timer.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 470f581eedd438..206418b6d7c48b 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -591,7 +591,9 @@ out_reset_timer: tcp_stream_is_thin(tp) && icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { icsk->icsk_backoff = 0; - icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); + icsk->icsk_rto = clamp(__tcp_set_rto(tp), + tcp_rto_min(sk), + TCP_RTO_MAX); } else if (sk->sk_state != TCP_SYN_SENT || icsk->icsk_backoff > READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) { |