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tcp: fix FIONREAD/SIOCINQ

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[ Upstream commit a3374c42aa ]

tcp_ioctl() tries to take into account if tcp socket received a FIN
to report correct number bytes in receive queue.

But its flaky because if the application ate the last skb,
we return 1 instead of 0.

Correct way to detect that FIN was received is to test SOCK_DONE.

Reported-by: Elliot Hughes <enh@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@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 2012-10-18 09:14:12 +00:00 committed by Greg Kroah-Hartman
parent 0f04b9af7c
commit d1a94e022b
1 changed files with 3 additions and 5 deletions
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8
net/ipv4/tcp.c
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@ -481,14 +481,12 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
!tp->urg_data ||
before(tp->urg_seq, tp->copied_seq) ||
!before(tp->urg_seq, tp->rcv_nxt)) {
struct sk_buff *skb;
answ = tp->rcv_nxt - tp->copied_seq;
/* Subtract 1, if FIN is in queue. */
skb = skb_peek_tail(&sk->sk_receive_queue);
if (answ && skb)
answ -= tcp_hdr(skb)->fin;
/* Subtract 1, if FIN was received */
if (answ && sock_flag(sk, SOCK_DONE))
answ--;
} else
answ = tp->urg_seq - tp->copied_seq;
release_sock(sk);