Hi zhenyuan,

Thanks for your patch.

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On 2021/9/17 11:40, jiazhenyuan wrote:

mainline inclusion from mainline-v5.3.0 commit 3256a2d6ab1f71f9a1bd2d7f6f18eb8108c48d17 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I4AFRJ?from=project-issue CVE: NA

---

tcp: adjust rto_base in retransmits_timed_out() The cited commit exposed an old retransmits_timed_out() bug which assumed it could call tcp_model_timeout() with TCP_RTO_MIN as rto_base for all states.

But flows in SYN_SENT or SYN_RECV state uses a different RTO base (1 sec instead of 200 ms, unless BPF choses another value)

This caused a reduction of SYN retransmits from 6 to 4 with the default /proc/sys/net/ipv4/tcp_syn_retries value.

Fixes: a41e8a8 ("tcp: better handle TCP_USER_TIMEOUT in SYN_SENT state") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Yuchung Cheng ycheng@google.com Cc: Marek Majkowski marek@cloudflare.com Signed-off-by: David S. Miller davem@davemloft.net

Signed-off-by: jiazhenyuan jiazhenyuan@uniontech.com

net/ipv4/tcp_timer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 681882a40968..81a47e87c35d 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -190,7 +190,7 @@ static bool retransmits_timed_out(struct sock *sk, unsigned int boundary, unsigned int timeout) {

• const unsigned int rto_base = TCP_RTO_MIN;

• unsigned int rto_base = TCP_RTO_MIN; unsigned int linear_backoff_thresh, start_ts;

  if (!inet_csk(sk)->icsk_retransmits)

@@ -201,6 +201,9 @@ static bool retransmits_timed_out(struct sock *sk, return false;

if (likely(timeout == 0)) {

• if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
  

•                    rto_base = tcp_timeout_init(sk);
  

• linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);

  if (boundary <= linear_backoff_thresh)