Commit 9c518c0e authored by Eric Dumazet's avatar Eric Dumazet Committed by Luis Henriques

tcp: tcp_make_synack() should clear skb->tstamp

commit b50edd78 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: 7faee5c0 ("tcp: remove TCP_SKB_CB(skb)->when")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 426b9be6
...@@ -2855,6 +2855,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, ...@@ -2855,6 +2855,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
} }
#endif #endif
/* Do not fool tcpdump (if any), clean our debris */
skb->tstamp.tv64 = 0;
return skb; return skb;
} }
EXPORT_SYMBOL(tcp_make_synack); EXPORT_SYMBOL(tcp_make_synack);
......
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