MTUBytes in systemd.link does not work?

enihcam · 2014-12-02 13:42:20

my .link file:

[Match]
Driver=r8168
[Link]
MTUBytes=1480

I turned off MTU-from-DHCP feature, but the MTU is still 1500 after reboot.

Any ideas?

Spider.007 · 2014-12-03 13:19:35

I have the same issue; networkctl status $DEV actually shows the default link rules are being used instead of my custom ones... what does yours say?

enihcam · 2014-12-03 23:38:04

Same

Spider.007 · 2014-12-04 10:57:38

For me it seems the .link somehow doesn't match properly; I found this to debug that:

# udevadm test-builtin net_setup_link /sys/class/net/enp2s0f2
calling: test-builtin
load module index
timestamp of '/etc/systemd/network' changed
Parsed configuration file /etc/systemd/network/brocade-mtu.link
Parsed configuration file /usr/lib/systemd/network/99-default.link
Created link configuration context.
ID_NET_DRIVER=bna
Config file /usr/lib/systemd/network/99-default.link applies to device enp2s0f2
ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
unload module index
Unloaded link configuration context.

Fwiw; my brocade-mtu.link file contains:

[Match]
Driver=bna

[Link]
MTUBytes=9000

falconindy · 2014-12-04 13:57:59

You must give your .link files names that order before 99-default.link, if you want them to have any effect. Anything starting with letters instead of digits will order after 9, so it won't have an effect.

Spider.007 · 2014-12-04 15:30:27

Ah; that does indeed seem to have a positive effect. It fixes udevadm:

calling: test-builtin
load module index
timestamp of '/etc/systemd/network' changed
Parsed configuration file /usr/lib/systemd/network/99-default.link
Parsed configuration file /etc/systemd/network/01-bna-mtu.link
Created link configuration context.
ID_NET_DRIVER=bna
Config file /etc/systemd/network/01-bna-mtu.link applies to device enp2s0f2
ID_NET_LINK_FILE=/etc/systemd/network/01-bna-mtu.link
unload module index
Unloaded link configuration context.

but it seems networkctl (even after restarting systemd-networkd) needs a reboot to pick up the changes

falconindy · 2014-12-05 00:37:59

Spider.007 wrote:

but it seems networkctl (even after restarting systemd-networkd) needs a reboot to pick up the changes

Probably because networkd doesn't apply link configuration (udev does this).

Spider.007 · 2014-12-06 11:08:56

falconindy wrote:

Spider.007 wrote:
but it seems networkctl (even after restarting systemd-networkd) needs a reboot to pick up the changes
Probably because networkd doesn't apply link configuration (udev does this).

Yep, this works fine. Thanks!

Arch Linux

#1 2014-12-02 13:42:20

MTUBytes in systemd.link does not work?

#2 2014-12-03 13:19:35

Re: MTUBytes in systemd.link does not work?

#3 2014-12-03 23:38:04

Re: MTUBytes in systemd.link does not work?

#4 2014-12-04 10:57:38

Re: MTUBytes in systemd.link does not work?

#5 2014-12-04 13:57:59

Re: MTUBytes in systemd.link does not work?

#6 2014-12-04 15:30:27

Re: MTUBytes in systemd.link does not work?

#7 2014-12-05 00:37:59

Re: MTUBytes in systemd.link does not work?

#8 2014-12-06 11:08:56

Re: MTUBytes in systemd.link does not work?

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