Default route changes unexpectedly

[Nick Rogers]

On Wed, Mar 6, 2013 at 12:25 AM, Andre Oppermann <andre at freebsd.org> wrote:
> 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?

I use PF for NAT, filtering, and rdr rules. ALTQ for bandwidth
management. I do not use netgraph. I use vlans. PF redirects to squid
as a transproxy. I'm not familiar with flow routing so unless its
enabled in 9.1 by default I do not use it.

>
> How frequent does this happen?
Every other day during periods of heavier Internet-bound traffic.

>
> 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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>>
>