[Xorp-users] Linux IPv6 MR

[Otto Solares]

On Tue, May 23, 2006 at 11:53:04PM -0700, Pavlin Radoslavov wrote:
> > The kernel shows this message:
> > 
> > KERNEL: assertion (newskb->dst) failed at net/ipv6/ip6_output.c (113)
> 
> It appears to be a kernel bug. For testing purpose can you try
> pim6sd and see whether you can still trigger that bug.
> BTW, I believe that mrd6 (the other IPv6 multicast routing
> alternative) performs the multicast forwarding in user
> space, hence it won't be a good candidate to test the bug.

Ok, will try both daemons and report back.

> Also, can you provide some additional info when the assertion is
> triggered. E.g., does it happen when the first data packet is
> forwarded, etc.

It actually starts when XORP's pim6d is launched, before
any forwarding attempt, that assertion floods the logs,
sometimes tenths of times per second and it nevers stops
until XORP is taken down.

> > Does somebody knows the state of IPv6 multicast
> > routing in XORP and in Linux kernel?
> 
> We have done very limited testing with an older USAGI snapshot.
> See the following email for details:
> http://mailman.icsi.berkeley.edu/pipermail/xorp-users/2005-November/000901.html

Yea, I used the information and links in that message for
"fixing" the mroute6.h header so XORP could compile IPv6
multicast routing support.

> > I'm not a routing expert but would like to know what
> > exactly the 'enable-ip-router-alert-option-check'
> > option do?  I don't see a difference with true or
> > false.  If enabled is much verbose the output.
> 
> If it is enabled, then certain PIM-SM control packets must have the
> IP Router Alert option set to be accepted, otherwise those packets
> will be dropped with a warning like:
> "RX %s from %s to %s on vif %s: missing IP Router Alert option"
> 
> If all appropriate PIM control messages from your PIM-SM neighbors
> contain the IP Router Alert message (as specified in the PIM-SM
> spec), then you won't see any difference even if you enable the
> enable-ip-router-alert-option-check option.

>From your experience, in necessary to disable in any modern
environment (with other linux, bsds, macosx, solaris, winxp)?

> Please let us know if you find anything about the kernel crash.

I will.  I posted in usagi-users, hopefully somebody will tell
me what's going on, if not, that daemon in user space you mention
would be the only option for IPv6 multicast routing in Linux.

> P.S. BTW, the static RP address in your configuration
> (fe80::205:5dff:fe7c:61fd) appears to be a link-local address.
> In general, this should be a domain-wide reachable address.

I questioned myself about this one, will fix it, thank you.

-otto