tcp: provide more information on the tcp receive_queue bugs

The addition of rcv_nxt allows to discern whether the skb
was out of place or tp->copied. Also catch fancy combination
of flags if necessary (sadly we might miss the actual causer
flags as it might have already returned).

Btw, we perhaps would want to forward copied_seq in
somewhere or otherwise we might have some nice loop with
WARN stuff within but where to do that safely I don't
know at this stage until more is known (but it is not
made significantly worse by this patch).

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 7 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 98440ad82558..f1813bc71088 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1183,7 +1183,9 @@ void tcp_cleanup_rbuf(struct sock *sk, int copied)
 #if TCP_DEBUG
         struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
 
-        WARN_ON(skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq));
+        WARN(skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq),
+             KERN_INFO "cleanup rbuf bug: copied %X seq %X rcvnxt %X\n",
+             tp->copied_seq, TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt);
 #endif
 
         if (inet_csk_ack_scheduled(sk)) {
@@ -1430,11 +1432,13 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                         /* Now that we have two receive queues this
                          * shouldn't happen.
                          */
-                        if (before(*seq, TCP_SKB_CB(skb)->seq)) {
-                                printk(KERN_INFO "recvmsg bug: copied %X "
-                                       "seq %X\n", *seq, TCP_SKB_CB(skb)->seq);
+                        if (WARN(before(*seq, TCP_SKB_CB(skb)->seq),
+                             KERN_INFO "recvmsg bug: copied %X "
+                                       "seq %X rcvnxt %X fl %X\n", *seq,
+                                       TCP_SKB_CB(skb)->seq, tp->rcv_nxt,
+                                       flags))
                                 break;
-                        }
+
                         offset = *seq - TCP_SKB_CB(skb)->seq;
                         if (tcp_hdr(skb)->syn)
                                 offset--;
@@ -1443,8 +1447,9 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                         if (tcp_hdr(skb)->fin)
                                 goto found_fin_ok;
                         WARN(!(flags & MSG_PEEK), KERN_INFO "recvmsg bug 2: "
-                                        "copied %X seq %X\n", *seq,
-                                        TCP_SKB_CB(skb)->seq);
+                                        "copied %X seq %X rcvnxt %X fl %X\n",
+                                        *seq, TCP_SKB_CB(skb)->seq,
+                                        tp->rcv_nxt, flags);
                 }
 
                 /* Well, if we have backlog, try to process it now yet. */