Commit bef5767f authored Apr 17, 2018 by Yuchung Cheng Committed by David S. Miller Apr 19, 2018

tcp: better delivery accounting for SYN-ACK and SYN-data



the tcp_sock:delivered has inconsistent accounting for SYN and FIN.
1. it counts pure FIN
2. it counts pure SYN
3. it counts SYN-data twice
4. it does not count SYN-ACK

For congestion control perspective it does not matter much as C.C. only
cares about the difference not the aboslute value. But the next patch
would export this field to user-space so it's better to report the absolute
value w/o these caveats.

This patch counts SYN, SYN-ACK, or SYN-data delivery once always in
the "delivered" field.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 415787d7

net/ipv4/tcp_input.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -5567,9 +5567,12 @@ static bool tcp_rcv_fastopen_synack(struct sock sk, struct sk_buff synack,
		return true;
		}
		tp->syn_data_acked = tp->syn_data;
		if (tp->syn_data_acked)
		NET_INC_STATS(sock_net(sk),
		LINUX_MIB_TCPFASTOPENACTIVE);
		if (tp->syn_data_acked) {
		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
		/* SYN-data is counted as two separate packets in tcp_ack() */
		if (tp->delivered > 1)
		--tp->delivered;
		}

		tcp_fastopen_add_skb(sk, synack);

		@@ -5901,6 +5904,7 @@ int tcp_rcv_state_process(struct sock sk, struct sk_buff skb)
		}
		switch (sk->sk_state) {
		case TCP_SYN_RECV:
		tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */
		if (!tp->srtt_us)
		tcp_synack_rtt_meas(sk, req);

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