On 6/28/25 11:04 AM, David C Rankin wrote:
here has definitely been a change in how (whatever) looks at IPv4 and
IPv6 and chooses the interface to use. Here is the same journal entries
from the last boot of kernel 6.15.3 and IPv4 is configured and stays UP.
So whatever happened, it looks like the logic governing whether to use
IPv4 or IPv6 changed in this last update and that is what is taking my
IPv4 interface down, e.g.
No, it's not an IPv4/IPv6 logic choice issue, it is simply that on
boot the interfaces is configured for IPv4 and brought up, but then is
immediately taken down again by something. The later manual bringing up
of the interface configured it as it has always been with mdns
registered for both IPv4 and IPv6. The difference being on manual
activation the interface stays up.
It's looking like there may have been a change in how systemd is
managing the interface. Something takes the interface back down during boot.
It is the boot activation where something has changed. The boot
entries are the Jun 28 02:17:05 journal entries:
Jun 28 02:17:05 valkyrie systemd[1]: Expecting device
/sys/subsystem/net/devices/enp5s0...
Jun 28 02:17:08 valkyrie kernel: r8169 0000:05:00.0 enp5s0: renamed from
eth0
Jun 28 02:17:12 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Down
Jun 28 02:17:15 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Up -
1Gbps/Full - flow control rx/tx
Jun 28 02:17:15 valkyrie avahi-daemon[711]: Joining mDNS multicast group
on interface enp5s0.IPv4 with address 192.168.6.14.
Jun 28 02:17:15 valkyrie avahi-daemon[711]: New relevant interface
enp5s0.IPv4 for mDNS.
Jun 28 02:17:15 valkyrie avahi-daemon[711]: Registering new address
record for 192.168.6.14 on enp5s0.IPv4.
Jun 28 02:17:15 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Down
Jun 28 02:17:15 valkyrie avahi-daemon[711]: Interface enp5s0.IPv4 no
longer relevant for mDNS.
Jun 28 02:17:15 valkyrie avahi-daemon[711]: Leaving mDNS multicast group
on interface enp5s0.IPv4 with address 192.168.6.14.
Jun 28 02:17:15 valkyrie avahi-daemon[711]: Withdrawing address record
for 192.168.6.14 on enp5s0.
Jun 28 02:17:18 valkyrie named[801]: listening on IPv4 interface enp5s0,
192.168.6.14#53
Comparing the later manual activation of the link on Jun 28 02:40:10,
with "ip link set enp5s0 up", the device comes right up as it always did
on boot before this last update:
Jun 28 02:40:10 valkyrie avahi-daemon[711]: Joining mDNS multicast group
on interface enp5s0.IPv4 with address 192.168.6.14.
Jun 28 02:40:10 valkyrie avahi-daemon[711]: New relevant interface
enp5s0.IPv4 for mDNS.
Jun 28 02:40:10 valkyrie avahi-daemon[711]: Registering new address
record for 192.168.6.14 on enp5s0.IPv4.
Jun 28 02:40:10 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Down
Jun 28 02:40:13 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Up -
1Gbps/Full - flow control rx/tx
Jun 28 02:40:14 valkyrie avahi-daemon[711]: Joining mDNS multicast group
on interface enp5s0.IPv6 with address fe80::feaa:14ff:fe9e:3319.
Jun 28 02:40:14 valkyrie avahi-daemon[711]: New relevant interface
enp5s0.IPv6 for mDNS.
Jun 28 02:40:14 valkyrie avahi-daemon[711]: Registering new address
record for fe80::feaa:14ff:fe9e:3319 on enp5s0.*.
That's confirmed by the journal entries from the boot after the June
25 update to 6.15.3, e.g.
Jun 25 03:49:36 valkyrie systemd[1]: Expecting device
/sys/subsystem/net/devices/enp5s0...
Jun 25 03:49:44 valkyrie kernel: r8169 0000:05:00.0 enp5s0: renamed from
eth0
Jun 25 03:49:48 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Down
Jun 25 03:49:50 valkyrie kernel: r8169 0000:05:00.0 enp5s0: Link is Up -
1Gbps/Full - flow control rx/tx
Jun 25 03:49:50 valkyrie avahi-daemon[729]: Joining mDNS multicast group
on interface enp5s0.IPv4 with address 192.168.6.14.
Jun 25 03:49:50 valkyrie avahi-daemon[729]: New relevant interface
enp5s0.IPv4 for mDNS.
Jun 25 03:49:50 valkyrie avahi-daemon[729]: Registering new address
record for 192.168.6.14 on enp5s0.IPv4.
Jun 25 03:49:52 valkyrie avahi-daemon[729]: Joining mDNS multicast group
on interface enp5s0.IPv6 with address fe80::feaa:14ff:fe9e:3319.
Jun 25 03:49:52 valkyrie avahi-daemon[729]: New relevant interface
enp5s0.IPv6 for mDNS.
Jun 25 03:49:52 valkyrie avahi-daemon[729]: Registering new address
record for fe80::feaa:14ff:fe9e:3319 on enp5s0.*.
The part that is different now is on boot after the device is brought
up, it's being brought back down, and it occurs with the LTS kernel and
the new 6.15.4 - so that should eliminate a kernel issue.
The only other changes that look relevant and would be common between
LTS boot and 6.15.4 are the firmware and systemd (257.6-1 -> 257.7-1)
updates. (this is my best educated guess). How would we confirm this and
then fix it?
--
David C. Rankin, J.D.,P.E.
