From bef5767f37cfe42b1cf1ae60f01cfb4e16a7a2b8 Mon Sep 17 00:00:00 2001
From: Yuchung Cheng <ycheng@google.com>
Date: Tue, 17 Apr 2018 23:18:46 -0700
Subject: [PATCH] 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>
---
net/ipv4/tcp_input.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f93687f97d805..2499248d4a679 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -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);
--
2.30.2