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tcp: do not enqueue skb with SYN flag

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If we remove the SYN flag from the skbs that tcp_fastopen_add_skb()
places in socket receive queue, then we can remove the test that
tcp_recvmsg() has to perform in fast path.

All we have to do is to adjust SEQ in the slow path.

For the moment, we place an unlikely() and output a message
if we find an skb having SYN flag set.
Goal would be to get rid of the test completely.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-02-01 21:03:08 -08:00 committed by David S. Miller
parent 61d2bcae99
commit 9d691539ee
2 changed files with 9 additions and 2 deletions
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8
net/ipv4/tcp.c
View File

@ -1466,8 +1466,10 @@ static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
offset = seq - TCP_SKB_CB(skb)->seq;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
pr_err_once("%s: found a SYN, please report !\n", __func__);
offset--;
}
if (offset < skb->len || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) {
*off = offset;
return skb;
@ -1657,8 +1659,10 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
break;
offset = *seq - TCP_SKB_CB(skb)->seq;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
if (unlikely(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
pr_err_once("%s: found a SYN, please report !\n", __func__);
offset--;
}
if (offset < skb->len)
goto found_ok_skb;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)

3
net/ipv4/tcp_fastopen.c
View File

@ -143,6 +143,9 @@ void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
__skb_pull(skb, tcp_hdrlen(skb));
skb_set_owner_r(skb, sk);
TCP_SKB_CB(skb)->seq++;
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
__skb_queue_tail(&sk->sk_receive_queue, skb);
tp->syn_data_acked = 1;