wg-quick up automation fails

[XRP]

On Sun, 2019-06-02 at 01:49 +0200, Silvan Nagl wrote:
> G'day,
> 
> i recently upgrade WireGuard to the latest shipped Debian version
> (0.0.20190406-1) and noticed my wg-quick created interface did not
> come
> up as usual anymore. (Also tried the git master branch) I tried to
> single command trough wg-quick's automation to reproduce the error;
> 
> automatic:
> 
> [#] ip link add Y type wireguard
> [#] wg setconf Y /dev/fd/63
> [#] ip address add X.X.X.X/32 dev Y
> [#] ip address add fc00::XXXX/128 dev Y
> [#] ip link set mtu XXXX up dev Y
> [#] resolvconf -a tun.Y -m 0 -x
> [#] wg set Y fwmark 51820
> [#] ip -6 route add ::/0 dev Y table 51820
> RTNETLINK answers: No such device
> [#] resolvconf -d tun.Y
> [#] ip link delete dev Y
> 
> manual:
> 
> > ip link add Y type wireguard
> > wg setconf Y <(wg-quick strip /etc/wireguard/Y.conf)
> > ip address add X.X.X.X/32 dev Y
> > ip address add fc00::XXXX/128 dev Y
> > ip link set mtu 1268 up dev Y
> > resolvconf -a tun.X -m 0 -x
> > wg set Y fwmark 51820
> > ip -6 route add ::/0 dev Y table 51820
> 
> < RTNETLINK answers: No such device
> 
> (MTU may be to low here so i set it higher again)
> 
> > ip link set mtu 1420 up dev Y
> > ip -6 route add ::/0 dev Y table 51820 (works now)
> 
> breaks up @ this point because of error handling...
> 
> Additionally it could be possible the MTU isn't set correctly.

I had a similar problem where I got a "RTNETLINK answers: No such
device" error. After that I tried to use the wg-quick version in the
master branch and that fixed my problem. I hope that helps.

(MTU for IPv6 must be 1280 bytes at least.)