[Xorp-hackers] MLD(v2) on Linux 2.6.26-rc7 kernel?

[Kevin Fall]

Hi.  Thanks for the response, but I believe I have found the root of  
the problem:

in mfea_proto_com.cc, at about line 2337 there is an assignment to  
_sndmh.msg_namelen.  This is for IPv6.  For IPv4, however,
there is an assignment to this field in addition to:

         _sndmh.msg_control      = NULL;
         _sndmh.msg_controllen   = 0;

So, if you add these lines to the IPv6 case, the sendmsg() call no  
longer fails, but there is a "bonus" core dump later on.

As a hacky fix, I basically made these fields null around the  
sendmsg() call and restored them to their previous values after
the call using a pair of temporary values.  This seems to work and  
indeed the system runs.

Of course, this isn't really a very clean fix.  So, I'd recommend  
somebody with a broader exposure to the whole code base (maybe you :) )
come up with something a little more "clean".  In any case, the root  
of the problem is the control fields not being set in a way the
kernel likes.

thx,
- K


On Jun 23, 2008, at Jun 238:06 PMPDT, Pavlin Radoslavov wrote:

> Kevin Fall <kfall at cs.berkeley.edu> wrote:
>
>> Hi folks.
>>
>> I've just this past weekend spun up Xorp to experiment with MLDv2 and
>> some other things.  After noticing the lack of v6 multicast routing  
>> in
>> Linux 2.6.25.x kernels, I build a more bleeding edge 2.6.26 (rc7)
>> kernel that has v6 multicast routing included-- or at least, says it
>> does.
>>
>> When I run Xorp 1.4 configured to do MLDv2 (on eth3), I see this:
>>
>> [ 2008/06/23 09:01:20 TRACE xorp_mld MLD6IGMP ] TX MLD_LISTENER_QUERY
>> from fe80::204:5aff:fe9f:9e80 to ff02::1
>> [ 2008/06/23 09:01:20  ERROR xorp_mld:21363 MLD6IGMP +1519
>> xrl_mld6igmp_node.cc mfea_client_send_protocol_message_cb ] Cannot
>> send a protocol message: 102 Command failed Cannot send MLD protocol
>> message from fe80::204:5aff:fe9f:9e80 to ff02::1 on vif eth3:
>> sendmsg(proto 58 size 28 from fe80::204:5aff:fe9f:9e80 to ff02::1 on
>> vif eth3) failed: Invalid argument
>>
>> So, before I spend hours digging to figure out just what this is,  
>> does
>> somebody already have an idea?
>
> Nothing obvious comes to mind. Do you see the problem if you
> configure to run MLDv1 instead of MLDv2?
>
> Could you try to run the latest XORP code from anon. CVS.
> Number of things have changed in the FEA since the 1.4 release, so
> there is some chance this problem is gone.
>
> BTW, what OS distribution/version are you using, and how did you
> update the kernel config: i.e., using a built-in mechanism like
> apt-get or just downloading from kernel.org and compiling by hand?
>
> Could you send your kernel .config file as well.
>
> Pavlin
>
>