[nos-bbs] Presence of IPV6 on tun interface & random JNOS crashes ?

[Maiko (Personal)]

There is a small chance that if you have IPV6 enabled, JNOS will
receive IPV6 packets over the tun interface, even if you have no
desire to run IPV6, I noticed in my trace when I enabled IPV6 on
my linux host system. Suddenly started seeing odd warnings, ie :

Tue Jan 31 19:15:52 2023 - tun1 recv:
IP: bad header
0000  60 09 0f 93 00 28 06 40 fd 00 00 04 00 00 00 00  `....(.@}.......
0010  00 00 00 00 00 00 00 01 fd 00 00 04 00 00 00 00  ........}.......
0020  00 00 00 00 00 00 00 02 97 22 00 17 d5 a9 df 4a  ........."..U)_J
0030  00 00 00 00 a0 02 fd 20 b9 38 00 00 02 04 05 a0  .... .} 98.....
0040  04 02 08 0a 0c 59 3f 27 00 00 00 00 01 03 03 07  .....Y?'........

The reason I suggest it 'might' be contributing to random crashes is
that the IP version is only checked after IP header extraction, which
means it had to parse data it was not meant to receive to find out the
type of data. Chances are probably it's not a big deal, but perhaps it
is something to rule out for those having random crash issues.

IF you can disable ipv6 on the tun interface between linux host and JNOS
itself, then see if that helps. I'll leave it up to you to figure out.

Maiko / VE4KLM