From: Kuniyuki Iwashima kuniyu@amazon.com

mainline inclusion from mainline-v6.6-rc1 commit d0f2b7a9ca0a1a89d65ee145815f89b54b7f977f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I65HYE

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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TCP socket saves the minimum required header length in tcp_header_len of struct tcp_sock, and later the value is used in __tcp_fast_path_on() to generate a part of TCP header in tcp_sock(sk)->pred_flags.

In tcp_rcv_established(), if the incoming packet has the same pattern with pred_flags, we enter the fast path and skip full option parsing.

The MD5 option is parsed in tcp_v[46]_rcv(), so we need not parse it again later in tcp_rcv_established() unless other options exist. We add TCPOLEN_MD5SIG_ALIGNED to tcp_header_len in two paths to avoid the slow path.

For passive open connections with MD5, we add TCPOLEN_MD5SIG_ALIGNED to tcp_header_len in tcp_create_openreq_child() after 3WHS.

On the other hand, we do it in tcp_connect_init() for active open connections. However, the value is overwritten while processing SYN+ACK or crossed SYN in tcp_rcv_synsent_state_process().

These two cases will have the wrong value in pred_flags and never go into the fast path.

We could update tcp_header_len in tcp_rcv_synsent_state_process(), but a test with slightly modified netperf which uses MD5 for each flow shows that the slow path is actually a bit faster than the fast path.

On c5.4xlarge EC2 instance (16 vCPU, 32 GiB mem)

$ for i in {1..10}; do ./super_netperf $(nproc) -H localhost -l 10 -- -m 256 -M 256; done

Avg of 10 * 36e68eadd303 : 10.376 Gbps * all fast path : 10.374 Gbps (patch v2, See Link) * all slow path : 10.394 Gbps

The header prediction is not worth adding complexity for MD5, so let's disable it for MD5.

Link: https://lore.kernel.org/netdev/20230803042214.38309-1-kuniyu@amazon.com/ Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/20230803224552.69398-2-kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Zhang Hao zhanghao383@huawei.com --- net/ipv4/tcp_minisocks.c | 2 -- net/ipv4/tcp_output.c | 5 ----- 2 files changed, 7 deletions(-)

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 21317f988d898..b9978f8e59cf4 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -541,8 +541,6 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, newtp->tsoffset = treq->ts_off; #ifdef CONFIG_TCP_MD5SIG newtp->md5sig_info = NULL; /*XXX*/ - if (treq->af_specific->req_md5_lookup(sk, req_to_sk(req))) - newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; #endif if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index d3093efc02958..f16040be22af1 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3717,11 +3717,6 @@ static void tcp_connect_init(struct sock *sk) if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps)) tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED;

-#ifdef CONFIG_TCP_MD5SIG - if (tp->af_specific->md5_lookup(sk, sk)) - tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; -#endif - /* If user gave his TCP_MAXSEG, record it to clamp */ if (tp->rx_opt.user_mss) tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;