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tcp: tcp_make_synack() should clear skb->tstamp

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[ Upstream commit b50edd7812 ]

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: 7faee5c0d5 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2015-04-09 13:31:56 -07:00 committed by Greg Kroah-Hartman
parent c31d60c297
commit ef15025a4e
1 changed files with 2 additions and 0 deletions
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2
net/ipv4/tcp_output.c
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@ -2772,6 +2772,8 @@ 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);