for reopen bug #8747 -- complete the fix

There was a bug #8747, http://bugzilla.kernel.org/show_bug.cgi?id=8747,

"MSG_ERRQUEUE messages do not pass to connected raw sockets",

which still is not fixed, due to absence of proper tests.

I've made an additional patch (attached), against the 2.6.24.4 tree. The patch fixes the issue completely for me. Tested.

Sorry that I have not checked up the previous attempt in real tests. I
assumed that the "typo" which I had found at that time (saddr/daddr
swapped) is just "a typo", and things "obviously" should work then...
Unfortunately, it seems that I am a first person who actually use
MSG_ERRQUEUE on connected ipv6 raw sockets. It is a reason why all the last years nobody reported this bug.

Note, that "connected raw sockets" is a good feature for new
traceroute(8) implementation for Linux (http://traceroute.sourceforge.net), included now into Fedora and other distros. This feature allows to filter all alien packets from the socket's input. Without this, the program will receive all the incoming raw packets (for the "icmp" and "tcp" tracerouting methods, which use raw sockets).

Because of that wrong assumption, I've implemented a check, whether the kernel version is more than 2.6.22.2, and if so, allow raw ipv6 sockets to connect. But since 2.6.22.2, the issue still not fixed, and now any combination of "traceroute >= 2.0.8" and "kernel >= 2.6.22.2" leads to impossibility to do "icmp" and "tcp" tracerouting for IPv6. :(

Now I have to ship an update for traceroute. If the bug can be fixed in the nearest future (note the patch is too simple), I'll just change the version to check. If not, I'll be compelled to drop the raw sockets connection for a while.

Regards,
Dmitry Butskoy
http://www.fedoraproject.org/wiki/DmitryButskoy
An upstream maintainer of http://traceroute.sourceforge.net

diff -Nrbu ipv6/icmp.c ipv6.OK/icmp.c
@@ -584,8 +584,8 @@
 	if (!pskb_may_pull(skb, inner_offset+8))
 		return;
 
-	saddr = &ipv6_hdr(skb)->saddr;
-	daddr = &ipv6_hdr(skb)->daddr;
+	saddr = &((struct ipv6hdr *)skb->data)->saddr;
+	daddr = &((struct ipv6hdr *)skb->data)->daddr;
 
 	/* BUGGG_FUTURE: we should try to parse exthdrs in this packet.
 	   Without this we will not able f.e. to make source routed