Re: network crash in nhop_free

On 01/08/2021 16:36, Alexander V. Chernikov wrote:
> 
> 
>> On 10 Jul 2021, at 10:07, Andriy Gapon <avg@FreeBSD.org> wrote:
>>
>> On 09/07/2021 00:02, Alexander V. Chernikov wrote:
>>> Hi Andriy,
>>> Could you by any chance provide a bit more info on the system networking configuration and the steps leading to panic?
>>> No chance for a coredump?
>>> destroy_nhgrp() suggests that there was a multipath route (default?) that was deleted.
>>> nhops are created with UMA_ALIGN_PTR, so I suspect there is a garbage inside nhgrp pointer..
>>
>> I've just reproduced the problem and got a crash dump.
>> The new panic is a little bit different, but I think that it confirms your analysis.
>> Also, you are right about the multipath route, although its creation was not intentional.
> 
> Should be fixed by https://cgit.freebsd.org/src/commit/?id=054948bd81bb9e4e32449cf351b62e501b8831ff .

I have to report that, unfortunately, as of main 
bb958dcf3d8af3a033dacbf8133681c9b0c73b2f I can still reproduce the same panic 
using the same steps.
To be clear, as I reported two similar but still distinct panics, it's the first 
panic, "Misaligned access from kernel space!".

I should also add that the commit message does not really match my scenario.
In my case routes do not change quite fast.  I have generous pauses between 
starting and stopping ppp.
I have a feeling that there must something more deterministic that leads to the 
crash.
  --
Andriy Gapon