From 20978981b4644bec1fcaeb90f61072a34f02d7c1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 9 Apr 2015 13:31:56 -0700 Subject: [PATCH] tcp: tcp_make_synack() should clear skb->tstamp [ Upstream commit b50edd7812852d989f2ef09dcfc729690f54a42d ] 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 20:28:58.502209 IP 127.0.0.2.23850 > 127.0.0.1.48245: S 3160535375:3160535375(0) ack 945476043 win 43690 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- 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 96f64e59d70c..8c70c73da347 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2796,6 +2796,8 @@ 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);