tcp: Try to catch MSG_PEEK bug

This patch tries to print out more information when we hit the
MSG_PEEK bug in tcp_recvmsg.  It's been around since at least
2005 and it's about time that we finally fix it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9b2756fbdf9b..90b2e0649bfb 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1442,7 +1442,9 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                                 goto found_ok_skb;
                         if (tcp_hdr(skb)->fin)
                                 goto found_fin_ok;
-                        WARN_ON(!(flags & MSG_PEEK));
+                        if (WARN_ON(!(flags & MSG_PEEK)))
+                                printk(KERN_INFO "recvmsg bug 2: copied %X "
+                                       "seq %X\n", *seq, TCP_SKB_CB(skb)->seq);
                 }
 
                 /* Well, if we have backlog, try to process it now yet. */