New: MSG_ERRQUEUE messages do not pass to connected raw sockets

http://bugzilla.kernel.org/show_bug.cgi?id=8747

           Summary: MSG_ERRQUEUE messages do not pass to connected raw
                    sockets
           Product: Networking
           Version: 2.5
     KernelVersion: 2.6.22
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV6
        AssignedTo: [email protected]
        ReportedBy: [email protected]

Problem Description:

It is related to the possibility to obtain MSG_ERRQUEUE messages from the udp and raw sockets, both connected and unconnected.

There is a little typo in net/ipv6/icmp.c code, which prevents such messages to be delivered to the errqueue of the correspond raw socket, when the socket is CONNECTED. The typo is due to swap of local/remote addresses.

Consider __raw_v6_lookup() function from net/ipv6/raw.c. When a raw socket is looked up usual way, it is something like:

sk = __raw_v6_lookup(sk, nexthdr, daddr, saddr, IP6CB(skb)->iif);

where "daddr" is a destination address of the incoming packet (IOW our local address), "saddr" is a source address of the incoming packet (the remote end).

But when the raw socket is looked up for some icmp error report, in net/ipv6/icmp.c:icmpv6_notify() , daddr/saddr are obtained from the echoed fragment of the "bad" packet, i.e. "daddr" is the original destination address of that packet, "saddr" is our local address. Hence, for icmpv6_notify() must use "saddr, daddr" in its arguments, not "daddr, saddr" ...

Steps to reproduce:

Create some raw socket, connect it to an address, and cause some error
situation: f.e. set ttl=1 where the remote address is more than 1 hop to reach. Set IPV6_RECVERR .
Then send something and wait for the error (f.e. poll() with POLLERR|POLLIN). You should receive "time exceeded" icmp message (because of "ttl=1"), but the socket do not receive it.

If you do not connect your raw socket, you will receive MSG_ERRQUEUE successfully. (The reason is that for unconnected socket there are no actual checks for local/remote addresses).