netdev - Re: Crash/hang in 5.4.47 with nexthop objects

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Message-ID: <b3c0ed6a-6a35-c18e-6321-1c56f126e13a@gmail.com>
Date:   Sun, 5 Jul 2020 17:09:37 -0600
From:   David Ahern <dsahern@...il.com>
To:     Brian Rak <brak@...opa.com>, netdev@...r.kernel.org
Subject: Re: Crash/hang in 5.4.47 with nexthop objects

[ sorry for the delay; was on PTO for a couple weeks ]

On 6/24/20 10:32 AM, Brian Rak wrote:
> Hi,
> 
> We're hitting an issue where the kernel with either hang indefinitely or
> immediately crash when IPv6 nexthops are used along with the `rpfilter`
> ip6tables module.  The following commands trigger this issue 100% of the
> time for us:
> 
> ip -6 route del default; ip -6 route del default; # repeat as necessary
> to remove all existing default routes
> ip6tables -t mangle -I PREROUTING 1 -m rpfilter --invert -j DROP
> ip nexthop add id 999 via 2001:19f0:1000:8080::1 dev eno1
> ip -6 route add default nhid 999

Thanks for the steps to reproduce; very helpful.

I think I found the problem; do you build your kernels to test a patch?