tcp: better SYNACK sent timestamp (9e450c1e) · Commits · 戴 / test

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 <ycheng@google.com> Signed-off-by:

Neal Cardwell <ncardwell@google.com> Signed-off-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

net/ipv4/tcp_output.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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();

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