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authorNeal Cardwell <ncardwell@google.com>2014-06-30 23:09:49 +0400
committerDavid S. Miller <davem@davemloft.net>2014-07-08 06:26:37 +0400
commit86c6a2c75ab97fe31844985169e26aea335432f9 (patch)
treee3d15ca2ac9a89fbd5399ac6a1886822176fc392 /include/net/tcp.h
parent0b88e7042a221a0318d726017b0f97aa42066826 (diff)
downloadlinux-86c6a2c75ab97fe31844985169e26aea335432f9.tar.xz
tcp: switch snt_synack back to measuring transmit time of first SYNACK
Always store in snt_synack the time at which the server received the first client SYN and attempted to send the first SYNACK. Recent commit aa27fc501 ("tcp: tcp_v[46]_conn_request: fix snt_synack initialization") resolved an inconsistency between IPv4 and IPv6 in the initialization of snt_synack. This commit brings back the idea from 843f4a55e (tcp: use tcp_v4_send_synack on first SYN-ACK), which was going for the original behavior of snt_synack from the commit where it was added in 9ad7c049f0f79 ("tcp: RFC2988bis + taking RTT sample from 3WHS for the passive open side") in v3.1. In addition to being simpler (and probably a tiny bit faster), unconditionally storing the time of the first SYNACK attempt has been useful because it allows calculating a performance metric quantifying how long it took to establish a passive TCP connection. Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Cc: Octavian Purdila <octavian.purdila@intel.com> Cc: Jerry Chu <hkchu@google.com> Acked-by: Octavian Purdila <octavian.purdila@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/tcp.h')
-rw-r--r--include/net/tcp.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0d5389aecf18..c9a75dbba0c7 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1093,7 +1093,7 @@ static inline 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 = 0;
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
req->mss = rx_opt->mss_clamp;
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
ireq->tstamp_ok = rx_opt->tstamp_ok;