Re: FreeBSD guest on Linux KVM, some vtnet(4) packets don't arrive

Michael Tuexen <[email protected]>
Newsgroups gmane.os.freebsd.devel.net
Message-ID <[email protected]>
> On 11. Apr 2026, at 14:09, Michael Tuexen <[email protected]> wrote:
> 
>> On 10. Apr 2026, at 23:34, Adrian Chadd <[email protected]> wrote:
>> 
>> On Fri, 10 Apr 2026 at 13:40, Michael Tuexen
>> <[email protected]> wrote:
>>> 
>>>> On 10. Apr 2026, at 12:21, Lexi Winter <[email protected]> wrote:
>>>> 
>>>> Lexi Winter wrote in <[email protected]>:
>>>>> the problem seems to be due to choice of cipher:
>>>>> 
>>>>> % ssh [email protected] [email protected]
>>>>> Fssh_ssh_dispatch_run_fatal: Connection to fd00:0:0:1::b port 22: message authentication code incorrect
>>>>> 
>>>>> % ssh [email protected] [email protected]
>>>>> Last login: Fri Apr 10 08:17:20 2026 from tansy.le-fay.org
>>>>> 
>>>>> if AES is broken, that would also explain why TLS doesn't work.
>>>>> 
>>>>> unfortunately while trying to rebuild world i ran into an unrelated
>>>>> panic[0], so i'll need to find a workaround for that before i can
>>>>> test more.
>>>> 
>>>> i was able to cross-build current main (82ff1c334b97) on another system
>>>> and copy it over, which seems to have fixed the issue with TLS and SSH.
>>>> 
>>>> i need to do some final setup on the VM and then i'll try to do some
>>>> more testing for the original vtnet/tcpdump problem, which is still
>>>> present.
>>> Hi Ivy,
>>> 
>>> is this really a vtnet/tcpdump problem? On my PPC64 VM, tcpdump does not
>>> show any packets on vtnet0 or lo0. On bare metal, tcpdump does not show
>>> any packets on lo0 or bge2.
>>> 
>>> So I guess, this has nothing to do with vtnet.
>> 
>> There's likely a bunch of weird broken stuff that we need to fix.
>> 
>> I'm pretty sure tcpdump worked fine in December last year on
>> ppc64le/ppc64be since I was doing
>> general fixing of stuff there.
>> 
>> Let's file some ppc64 bugs and get them triaged/debugged. I bet the
>> "why's tcpdump not working?"
>> problem is triagable with dtrace/fbt points.
> Some more testing:
> 1. 15.0 shows the same behavior as CURRENT
> 2. It is not that tcpdump is not working at all, it just shows the
>   packets in a batch after some time. Use ping -s 16000 127.0.0.1
>   and you see what I mean. Just using ping requires you to wait
>   substantially longer.
>   So it seems that tcpdump gets the packets on PPC64 only when some
>   buffer is full.

Using --immediate as a command line argument of tcpdump works around
the problem.

Best regards
Michael
> 
> Best regards
> Michael
>> 
>> 
>> 
>> -adrian
> 
>
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