wg-quick up (on linux) fails in case of several default routes

[Chris]

Hello Jason,

setup is
two default routes with diffenrent metrics (the second being the failover in 
case the lower metric connection goes down).
For good reasons wg-quick will setup an individual route to the wg server (for 
the possibility of changing th default route afterwards).
However wg-quick fails:

******log follows***********
wg-quick up wg_client
[#] ip link add wg_client type wireguard
[#] wg setconf wg_client /dev/fd/63
[#] ip -4 address add 10.0.129.200/24 dev wg_client
[#] ip link set mtu 1420 up dev wg_client
[#] GATEW=$(ip route list 0.0.0.0/0|sed -n 's/.* via \(.*\) dev.*/\1/p');route 
add s1.spam-free.eu gw $GATEW
SIOCADDRT: No such device
[#] ip link delete dev wg_client
******log  end  ***********

The point is, that GATEW is NOT a single address but rather a list of ip 
addresses and the command setting the route fails.

Instead one should always run through ALL default gateways and set individual 
routes to the server through ALL the default gateways with the same metric as 
the respective default route.
This will then also work in case the failover route is in operation.

Of course, tearing down the client should delete ALL individual routes to the 
server.
Hope this clarifies is a bit.

Cheers,
Chris

On 06/10/2020 14:20, Jason A. Donenfeld wrote:
> On Mon, Oct 5, 2020 at 3:51 PM Chris <wireguard at spam-free.eu> wrote:
>> wg-quick tries to set the route to the wg server through the default gateway.
> On Linux? It shouldn't be iterating default gateways at all, but
> rather using suppress_prefix. Can you provide more technical
> information about what you're seeing and maybe a patch to fix the
> issue?
>
> Jason