[Babel-users] Investigating a babeld crash on OpenWRT

[Baptiste Jonglez]

On Sun, Jul 13, 2014 at 03:06:55PM +0200, Juliusz Chroboczek wrote:
> > Since this runs inside tmux, the last 2000 lines of log should still be
> > there if babeld ever crashes again.
> 
> I doubt it will do you much good in case of a crash.  It would be really
> helpful to get a backtrace (ulimit -c somethingreasonable).

Unfortunately, core dumps are not enabled by default on OpenWRT, and I
really don't want to reflash it remotely.

Anyway, here are babeld famous last words:

Checking neighbours.
Sending self update to tap-babel.
Sending update to tap-babel for 10.0.0.0/8.
Sending update to tap-babel for 172.22.0.0/15.
Sending update to tap-babel for 172.23.184.64/26.
Sending update to tap-babel for 172.31.0.0/16.
kernel_route: flush 172.23.184.216/125 metric 0 dev 54 nexthop 172.23.184.217
Netlink message: (ACK)
kernel_route: add 172.23.184.216/125 metric 65535 dev 54 nexthop 172.23.184.217
Netlink message: (ACK)
Segmentation fault


The subnet is actually 172.23.184.216/29, not /125, but babeld seems to be
using IPv4-mapped addresses.  The RIB just before the segfault looked like
this:

  http://paste.debian.net/hidden/77ec723f/

Looking at the RIB, I'm not sure why babeld decided to change the kernel
route to unreachable.  Please note that the originator of this route (the
"fe80::23:184:217" neighbour) has a very spotty network connectivity.

The command line used to run babeld:

babeld -I /var/run/babeld.pid -g 33123 -C 'interface tap-babel split-horizon false max-rtt-penalty 250 rtt-max 500' -C 'interface tun-mejis wired true rxcost 45 enable-timestamps true' -C 'redistribute ip 172.23.184.0/24 le 29 proto 2 allow'  -C '  redistribute ip 10.0.0.0/8 eq 8  metric 255'  -C 'redistribute ip 172.22.0.0/15 eq 15  metric 128'  -C '  redistribute ip 172.31.0.0/16 eq 16  metric 255'  -C '  redistribute local  deny'  -C '  in ip 172.22.0.0/15  allow' -C '  in  deny'  -d 3

Any idea?

Thanks,
Baptiste
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