Re: Missing routes cause BUG() in icmpv6_xmit_lock().

["David S. Miller" <davem@xxxxxxxxxx>]

On Sun, 31 Aug 2003 22:44:54 -0700
"David S. Miller" <davem@xxxxxxxxxx> wrote:

> I'll see what I can do about this one.

Ok, here is the fix I'm going to use.  I actually inadvertantly
added this problem when I converted net/ipv6/icmp.c over to
per-cpu sockets.

There is nothing we could do with such ICMP destination unreachable
packets anyways, so dropping them is the right thing to do.

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
#                  ChangeSet    1.1614  -> 1.1615 
#            net/ipv6/icmp.c    1.26    -> 1.27   
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/09/01      davem@xxxxxxxxxxxxxx    1.1615
# [IPV6]: Do not BUG() on icmp6 socket contention, just drop.
# --------------------------------------------
#
diff -Nru a/net/ipv6/icmp.c b/net/ipv6/icmp.c
--- a/net/ipv6/icmp.c   Mon Sep  1 01:36:39 2003
+++ b/net/ipv6/icmp.c   Mon Sep  1 01:36:39 2003
@@ -95,8 +95,15 @@
 static void icmpv6_xmit_lock(void)
 {
        local_bh_disable();
-       if (unlikely(!spin_trylock(&icmpv6_socket->sk->lock.slock)))
-               BUG();
+       if (unlikely(!spin_trylock(&icmpv6_socket->sk->lock.slock))) {
+               /* This can happen if the output path (f.e. SIT or
+                * ip6ip6 tunnel) signals dst_link_failure() for an
+                * outgoing ICMP6 packet.
+                */
+               local_bh_enable();
+               return 1;
+       }
+       return 0;
 }
 
 static void icmpv6_xmit_unlock(void)
@@ -340,7 +347,8 @@
        fl.fl_icmp_type = type;
        fl.fl_icmp_code = code;
 
-       icmpv6_xmit_lock();
+       if (icmpv6_xmit_lock())
+               return;
 
        if (!icmpv6_xrlim_allow(sk, type, &fl))
                goto out;
@@ -423,7 +431,8 @@
        fl.oif = skb->dev->ifindex;
        fl.fl_icmp_type = ICMPV6_ECHO_REPLY;
 
-       icmpv6_xmit_lock();
+       if (icmpv6_xmit_lock())
+               return;
 
        if (!fl.oif && ipv6_addr_is_multicast(&fl.fl6_dst))
                fl.oif = np->mcast_oif;