Dear netdev people,
I updated one of my APU2 boxes yesterday and was confronted with an
interesting problem: With (Debian) Kernel 5.9.6 VLAN interfaces on top
of a bond on top of two I210 NICs are working only one way (outbound)
unless the VLAN interface is in promisc mode.
The setup looks like this
enp1s0 enp2s0
\ /
\ /
\ /
bond0 (LACP L3+4)
/ \
/ \
/ \
vlan23 vlan42
Traffic leaving the box (ARP, ND, OSPF Hellos, ...) works fine
according to tcpdump on a connected device, but inbound traffic only
seems to reach the system when vlanXX is in promisc mode. If I do a
tcpdump on vlanXX with --no-promiscuous-mode, I can confirm that there
only are outbound packets and none of the ARP replies etc. sent by the
remote box. On bond0 as well as on the physical NICs I see the same
behaviour (+ LACP frames on the NICs).
I did some tests to pinpoint the problem:
* VLAN interfaces on top of the physical NIC work fine
* LACP seems to work fine, slow/fast don't make a difference
* Disabling all offloading I could disable didn't make it work
(especially rxvlan)
* With (Debian) kernel 5.8.10 it works
* /proc/net/dev shows no rx errors or drops at all only one TX drop
on the VLAN interfaces
I couldn't find anything suspicous on the box neither in the logs nor
in ip -d link etc. Is this a know bug? If not should I test anything
specific or maybe do a git bisect between the kernel versions?
Kind regards
Max
--
"Does it bother me, that people hurt others, because they are to weak to face
the truth? Yeah. Sorry 'bout that."
-- Thirteen, House M.D.
