Re: FreeBSD guest on Linux KVM, some vtnet(4) packets don't arrive
Date: Wed, 08 Apr 2026 15:39:27 UTC
Zhenlei Huang wrote in <28495B68-0BD1-4372-806C-C766DBCB8410@FreeBSD.org>:
> > a route exists for this on the host:
> >
> > fd00:0:0:1::b via fe80::2 dev vm-ppc64-main proto bird metric 32 pref medium
>
> Just to confirm, do you have a reverse route on the guest ?
no, in fact, this was the problem. after adding a default route on the
guest side:
# route add -inet6 default fe80::1%vtnet0
... now everything is working fine. thanks! but i failed to notice
that problem because of the tcpdump issue, which is still present...
> That puzzled me a bit. If the net stack sees the arriving packets, then tcpdump shall
> intercept them correctly.
even with the network working, tcpdump is still not showing any packets.
i have no idea what's going on here or even where to start looking.
i'm currently installing a ppc64le guest on the same host to see if that
behaves any differently.
> Does `netstat -sp ip6` and `netstat -sp icmp6` show anything unusual ?
root@ppc64-main:~ # netstat -sp ip6
ip6:
18 total packets received
0 with size smaller than minimum
0 with data size < data length
0 with bad options
0 with incorrect version number
0 fragments received
0 fragments dropped (dup or out of space)
0 fragments dropped after timeout
0 fragments that exceeded limit
0 atomic fragments
0 packets reassembled ok
15 packets for this host
0 packets forwarded
0 packets not forwardable
0 redirects sent
20 packets sent from this host
0 packets sent with fabricated ip header
0 output packets dropped due to no bufs, etc.
0 output packets discarded due to no route
0 output datagrams fragmented
0 fragments created
0 datagrams that can't be fragmented
0 packets that violated scope rules
0 multicast packets which we don't join
Input histogram:
hop by hop: 18
Mbuf statistics:
0 one mbuf
18 one ext mbuf
0 two or more ext mbuf
0 packets whose headers are not contiguous
0 tunneling packets that can't find gif
0 packets discarded because of too many headers
0 failures of source address selection
source addresses on an outgoing I/F
4 addresses scope=0
source addresses on a non-outgoing I/F
3 addresses scope=0
source addresses of same scope
3 addresses scope=0
source addresses of a different scope
4 addresses scope=0
Source addresses selection rule applied:
10 first candidate
t@ppc64-main:~ # netstat -sp icmp6
icmp6:
0 calls to icmp6_error
0 errors not generated in response to an icmp6 message
0 errors not generated because of rate limitation
Output histogram:
echo: 8
neighbor solicitation: 2
neighbor advertisement: 2
MLDv2 listener report: 2
0 messages with bad code fields
0 messages < minimum length
0 bad checksums
0 messages with bad length
0 total packets dropped due to failed NDP resolution
Input histogram:
unreach: 3
time exceed: 3
echo reply: 8
neighbor solicitation: 2
neighbor advertisement: 2
Histogram of error messages to be generated:
0 no route
0 administratively prohibited
0 beyond scope
0 address unreachable
0 port unreachable
0 packet too big
0 time exceed transit
0 time exceed reassembly
0 erroneous header field
0 unrecognized next header
0 unrecognized option
0 redirect
0 unknown
0 message responses generated
0 messages with too many ND options
0 messages with bad ND options
0 bad neighbor solicitation messages
0 bad neighbor advertisement messages
0 bad router solicitation messages
0 bad router advertisement messages
0 bad redirect messages
0 default routers overflows
0 prefix overflows
0 neighbour entries overflows
0 redirect overflows
0 messages with invalid hop limit
0 path MTU changes