Default route changes unexpectedly

[Andre Oppermann]

On 05.03.2013 18:39, Nick Rogers wrote:
> Hello,
>
> I am attempting to create awareness of a serious issue affecting users
> of FreeBSD 9.x and PF. There appears to be a bug that allows the
> kernel's routing table to be corrupted by traffic routing through the
> system. Under heavy traffic load, the default route can seemingly
> randomly change to an IP address that is not directly connected to the
> network (i.e., is not configured anywhere). Dhclient is not in the
> mix, nor is routed, bgpd, etc. Running `route monitor` shows no
> evidence of the change in the default route. The one commonality
> between all the systems experiencing this problem seems to be the use
> of PF.
>
> Obviously this is a serious problem as it causes all Internet-bound
> traffic to stop routing until the default route is corrected. Some
> users, including myself, are working around this problem by installing
> a script that runs multiple times a second to check if the default
> route is incorrect and fixing it if necessary, which mitigates the
> amount of downtime caused by the bug.

Can you describe your traffic forwarding setup in more detail?
Is it only pf, or do you run netgraph, or other things as well?
Do you use flow routing?

How frequent does this happen?

I'm trying to create a stack graph to see which parts of the network
stack are involved in handling your packet.

-- 
Andre

> Please refer to these past posts for more examples and evidence of
> other users experiencing this problem:
>
> http://forums.freebsd.org/showthread.php?p=211610#post211610
>
> http://freebsd.1045724.n5.nabble.com/Default-route-quot-random-quot-gateway-modification-bug-td5750820.html
>
> http://lists.freebsd.org/pipermail/freebsd-net/2012-March/031879.html
>
> http://lists.freebsd.org/pipermail/freebsd-ipfw/2010-September/004361.html
>
> There is also a PR that was incorrectly labeled as an IPFW issue.
> Myself and others believe this issue is not restricted to the use of
> IPFW and that the PR should be relabeled. I am inclined to think it is
> strictly a PF issue since I am not using IPFW, however there is
> evidence of the default route changing on people using IPFW for past
> versions of FreeBSD (7.x/8.x), so perhaps this is related.
>
> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/174749
>
> Another PR for the same problem but specific to IPFW and 8.2-RELEASE
>
> http://www.freebsd.org/cgi/query-pr.cgi?pr=157796
>
> I am hoping someone reading this can give the problem the attention it
> deserves. Thank you.
>
> -Nick
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