[Xorp-hackers] Question on fea's use of sendmsg

[Pavlin Radoslavov]

Ben Greear <greearb at candelatech.com> wrote:

> I'm seeing a strange problem where the fea attempts to send
> a packet, the sendmsg returns a correct positive number,
> but I don't see the packet on the wire.
> 
> I do see multicast pkts from this same host, and I have set
> up an independent udp connection between these two interfaces
> and traffic flows fine (routing & interfaces seem functional.)
> 
> I can't find anything obvious in the man pages, so I was wondering
> if any of you have any ideas for what might be happening?

Are you using SO_BINDTODEVICE to bind the socket to a particular
interface?

Also, are those unicast or multicast packets?
One thing you could do is run tcpdump on all possible interfaces
(including the loopback interface), and see if the packets pops up
from some unexpected place.
It is better if you run tcpdump on the XORP host itself to avoid any
side effects.
You might also want to watch for some other clues like ARP messages
(e.g., if the destination is unicast).

Regards,
Pavlin