| Date | Mon, 25 Mar 2013 01:05:32 +0000 | From | Ben Hutchings <> | Subject | [ 008/104] tcp: fix double-counted receiver RTT when leaving receiver fast path |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Neal Cardwell <ncardwell@google.com>
[ Upstream commit aab2b4bf224ef8358d262f95b568b8ad0cecf0a0 ]
We should not update ts_recent and call tcp_rcv_rtt_measure_ts() both before and after going to step5. That wastes CPU and double-counts the receiver-side RTT sample.
Signed-off-by: Neal Cardwell <ncardwell@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- net/ipv4/tcp_input.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5494,6 +5494,9 @@ int tcp_rcv_established(struct sock *sk, if (tcp_checksum_complete_user(sk, skb)) goto csum_error; + if ((int)skb->truesize > sk->sk_forward_alloc) + goto step5; + /* Predicted packet is in window by definition. * seq == rcv_nxt and rcv_wup <= rcv_nxt. * Hence, check seq<=rcv_wup reduces to: @@ -5505,9 +5508,6 @@ int tcp_rcv_established(struct sock *sk, tcp_rcv_rtt_measure_ts(sk, skb); - if ((int)skb->truesize > sk->sk_forward_alloc) - goto step5; - NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); /* Bulk data transfer: receiver */
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