Commit 0aea76d3 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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tcp: SYN packets are now simply consumed

We now have proper per-listener but also per network namespace counters
for SYN packets that might be dropped.

We replace the kfree_skb() by consume_skb() to be drop monitor [1]
friendly, and remove an obsolete comment.
FastOpen SYN packets can carry payload in them just fine.

[1] perf record -a -g -e skb:kfree_skb sleep 1; perf report

Signed-off-by: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent 1bc7fe64
......@@ -5815,24 +5815,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
return 1;
/* Now we have several options: In theory there is
* nothing else in the frame. KA9Q has an option to
* send data with the syn, BSD accepts data with the
* syn up to the [to be] advertised window and
* Solaris 2.1 gives you a protocol error. For now
* we just ignore it, that fits the spec precisely
* and avoids incompatibilities. It would be nice in
* future to drop through and process the data.
* Now that TTCP is starting to be used we ought to
* queue this data.
* But, this leaves one open to an easy denial of
* service attack, and SYN cookies can't defend
* against this problem. So, we drop the data
* in the interest of security over speed unless
* it's still in use.
return 0;
goto discard;
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