| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 008/180] tcp: tcp_make_synack() should clear skb->tstamp | Date | Thu, 7 May 2015 10:43:37 +0100 |
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3.16.7-ckt11 -stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
commit b50edd7812852d989f2ef09dcfc729690f54a42d upstream.
I noticed tcpdump was giving funky timestamps for locally generated SYNACK messages on loopback interface.
11:42:46.938990 IP 127.0.0.1.48245 > 127.0.0.2.23850: S 945476042:945476042(0) win 43690 <mss 65495,nop,nop,sackOK,nop,wscale 7>
20:28:58.502209 IP 127.0.0.2.23850 > 127.0.0.1.48245: S 3160535375:3160535375(0) ack 945476043 win 43690 <mss 65495,nop,nop,sackOK,nop,wscale 7>
This is because we need to clear skb->tstamp before entering lower stack, otherwise net_timestamp_check() does not set skb->tstamp.
Fixes: 7faee5c0d514 ("tcp: remove TCP_SKB_CB(skb)->when") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- net/ipv4/tcp_output.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 1ea0a07ab0b5..144af9539ceb 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2855,6 +2855,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, } #endif + /* Do not fool tcpdump (if any), clean our debris */ + skb->tstamp.tv64 = 0; return skb; } EXPORT_SYMBOL(tcp_make_synack);
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