Detecting spurious SYNACK timeout using timestamp option requires recording the exact SYNACK skb timestamp. Previously the SYNACK sent timestamp was stamped slightly earlier before the skb was transmitted. This patch uses the SYNACK skb transmission timestamp directly.
Signed-off-by: Yuchung Cheng <[email protected]> Signed-off-by: Neal Cardwell <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> --- net/ipv4/tcp_input.c | 2 +- net/ipv4/tcp_output.c | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 695f840acc14..30c6a42b1f5b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6319,7 +6319,7 @@ static void tcp_openreq_init(struct request_sock *req, req->cookie_ts = 0; tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq; tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; - tcp_rsk(req)->snt_synack = tcp_clock_us(); + tcp_rsk(req)->snt_synack = 0; tcp_rsk(req)->last_oow_ack_time = 0; req->mss = rx_opt->mss_clamp; req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 32061928b054..0c4ed66dc1bf 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3247,7 +3247,11 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, skb->skb_mstamp_ns = cookie_init_timestamp(req); else #endif + { skb->skb_mstamp_ns = tcp_clock_ns(); + if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */ + tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb); + } #ifdef CONFIG_TCP_MD5SIG rcu_read_lock(); -- 2.21.0.593.g511ec345e18-goog
