Bug 678184 – net-misc/netifrc-0.6.1: WireGuard interfaces do not set mtu

• Product: Gentoo Hosted Projects
• Status: UNCONFIRMED ---

[Description tastytea 2019-02-16 23:06:56 UTC]

I wanted to change the mtu on a WireGuard interface. The setting "mtu_wg0" had no effect.

Reproducible: Always

Steps to Reproduce:
1. Configure wg0 as WireGuard interface in /etc/conf.d/net
2. Set mtu_wg0="1400"
3. start net.wg0
Actual Results:  
mtu is 1420

Expected Results:  
mtu is 1400

My config:

config_wg0="fd23::10:1:3/64 10.23.10.13/16"
wireguard_wg0="/etc/wireguard/wg0.conf"
mtu_wg0="1400"

[Comment 1 Ben Kohler 2019-07-10 14:43:25 UTC]

*** Bug 677940 has been marked as a duplicate of this bug. ***

[Comment 2 Katherine Peeters 2021-07-19 22:03:13 UTC]

I have the same issue on all of my Gentoo machines. Additionally, after a recent update (?) the MTU is no longer set correctly automatically, causing breakage. This means that every single time I boot any of my devices I have to log in as root and manually correct the MTU.

From what I can tell, netifrc is attempting to set the MTU before the interface has even been created, suggesting that this is not a Wireguard bug, but rather a netifrc bug. Either way, it's a problem...

[Comment 3 tastytea 2021-07-20 09:28:17 UTC]

Does the workaround from bug 677940 work for you? It works for me with netifrc 0.7.3.

postup() {
    case ${IFACE} in
        wg*)
            ip link set mtu 1400 dev ${IFACE}
        ;;
    esac
}

[Comment 4 lmk 2022-11-22 22:43:52 UTC]

Alternative solution that works for me is changing wireguard_depend() function in /lib/netifrc/net/wireguard to:

wireguard_depend()
{
    program /usr/bin/wg
    before interface
}