Patchwork [196/241] tcp: fix FIONREAD/SIOCINQ

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Submitter Herton Ronaldo Krzesinski
Date Dec. 13, 2012, 1:59 p.m.
Message ID <1355407206-17100-197-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/206042/
State New
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Comments

Herton Ronaldo Krzesinski - Dec. 13, 2012, 1:59 p.m.
3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

commit a3374c42aa5f7237e87ff3b0622018636b0c847e upstream.

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: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 net/ipv4/tcp.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Patch

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 56e9fa7..d758741 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -546,14 +546,12 @@  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);