#20393: netifd fails set MTU on VLAN devices
-------------------------+----------------------------------
Reporter: stintel | Owner: developers
Type: defect | Status: new
Priority: normal | Milestone: Chaos Calmer (trunk)
Component: base system | Version: Trunk
Keywords: |
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When changing the MTU for a VLAN interface in /etc/config/network, the MTU
is never actually set. Tried both old and new style config
(https://lists.openwrt.org/pipermail/openwrt-
devel/2014-September/027941.html).
Old:
{{{
config interface 'mgmt'
option ifname 'eth0.51'
option mtu '9000'
option proto 'static'
option ipaddr '192.168.51.254'
option netmask '255.255.255.0'
option ip6assign '64'
option ip6hint '51'
}}}
New:
{{{
config device 'eth0.51'
option type '8021q'
option ifname 'eth0'
option name 'eth0.51'
option vid '51'
option mtu '9000'
config interface 'mgmt'
option ifname 'eth0.51'
option proto 'static'
option ipaddr '192.168.51.254'
option netmask '255.255.255.0'
option ip6assign '64'
option ip6hint '51'
}}}
With either of the above configurations, running {{{ ifdown mgmt; ifup
mgmt }}} will not change the MTU for eth0.51:
{{{
root@ar0:~# ip link show dev eth0.51
48: eth0.51@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
state UP mode DEFAULT group default
link/ether 04:18:d6:31:38:b3 brd ff:ff:ff:ff:ff:ff
}}}
Changing the MTU manually doesn't work either:
{{{
root@ar0:~# ip link set mtu 9000 dev eth0.51
RTNETLINK answers: Numerical result out of range
}}}
This is because the MTU of the master interface is still on 1500. When I
manually change the MTU of the master interface first, I can change the
MTU of the VLAN interface as well:
{{{
root@ar0:~# ip link set mtu 9000 dev eth0.51
root@ar0:~# ip link show dev eth0.51
48: eth0.51@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue
state UP mode DEFAULT group default
link/ether 04:18:d6:31:38:b3 brd ff:ff:ff:ff:ff:ff
}}}
Once the MTU for the master interface is on 9000, both the old and new
style configuration as shown above work fine. When running {{{ ifdown
mgmt; ifup mgmt }}} afterwards, the eth0.51 interface comes back up with
MTU 9000.
Netifd should check the MTU of the master interface and change it if
needed, before trying to set the MTU of the VLAN interface.
--
Ticket URL: <https://dev.openwrt.org/ticket/20393>
OpenWrt <http://openwrt.org>
Opensource Wireless Router Technology
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