Am 22.05.20 um 17:58 schrieb Andrei Borzenkov:
The problem is, that sysctl.conf is being executed before the interfaces
get their eventual names.
That sounds like actual bug. What systemd version do you use?
At least it is, what the journal suggest, as seen below. However,
generally it sounds like a good idea to read sysctl.conf as early as
possible
As for my version:
$ pacman -Qs systemd
local/systemd 245.5-2
system and service manager
local/systemd-libs 245.5-2
systemd client libraries
local/systemd-sysvcompat 245.5-2
sysvinit compat for systemd
$ uname -a
Linux willy 5.6.13-arch1-1 #1 SMP PREEMPT Thu, 14 May 2020 06:52:53
+0000 x86_64 GNU/Linux
Same issues with the arch lts-kernel, this behaviour is consistent and
easily reproducable.
And the logs read:
journalctl -b0 | grep -E 'sysctl|ens3|eth0'
08:56:46 systemd[263]: systemd-sysctl.service: Executing:
/usr/lib/systemd/systemd-sysctl
08:56:46 systemd-sysctl[263]: Couldn't write '2' to
'net/ipv6/conf/ens3/addr_gen_mode', ignoring: No such file or directory
08:56:46 systemd-sysctl[263]: Couldn't write '2' to
'net/ipv6/conf/ens3/use_tempaddr', ignoring: No such file or directory
08:56:47 kernel: virtio_net virtio0 ens3: renamed from eth0
08:56:47 systemd[1]: sys-subsystem-net-devices-ens3.device: Changed dead
-> plugged
08:56:47 systemd[1]:
sys-devices-pci0000:00-0000:00:03.0-virtio0-net-ens3.device: Changed
dead -> plugged
08:56:51 systemd-networkd[459]: ens3: Interface name change detected,
ens3 has been renamed to eth0.
I wonder where this comes from.
08:56:51 systemd-networkd[459]: eth0: Interface name change detected,
eth0 has been renamed to ens3.
08:56:51 systemd-networkd[459]: ens3: IPv6 successfully enabled
08:56:51 systemd-networkd[459]: ens3: Link UP
08:56:51 systemd-networkd[459]: ens3: Gained carrier
...
Same wonders here, but, despite the mysterial double renaming,
systemd-sysctl is still being called before even the first rename. A
good second here. So I have no chance to set any values for ens3 at all.
udev applies sysctl just once - when interface first appears.
Any deeper insight on this? I was under the impression, sysctl is read
by systemd-sysctl only and not by udev at all? But admittedly, I am not
very knowledgable here. So I'd like to improve.
using final name (that can be different from initial kernel name). So if
device appeared under eth0 and got name ens3 during event procesing,
udev applies sysctl to ens3 and never to eth0. If udev applied settings
to eth0 before rename, these settings would be preserved after rename.
That does at least not correspond to my observation.
It seems, the kernel creates
net/ipv6/conf/eth0/use_tempaddr
upon detection and after renaming,
net/ipv6/conf/ens3/use_tempaddr
does not keep the values.
Is there a way to make systemd-sysctl a bit more verbose, so we can see
wether the eth0 setting are actually being applied?
So far we only see the error from ens3, but no positives from the eth0
settings.
Nonetheless, this would still impose a problem. As the eth* names are
not reliable, faking a setting intended for ens3 to eth0 in sysctl.conf
is a bit risky and most likely not the idea behind the whole renaming
thingy.
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