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Subject: Re: multiple wg interface in different namespace
To: Quan Zhou <quanzhou822@gmail.com>, wireguard@lists.zx2c4.com
References: <CAMRLKH-8fEJ9Cv9rMT2u3sv0oUqu1dD++xXV51dZh3CxmCHBsg@mail.gmail.com>
From: Samuel Holland <samuel@sholland.org>
Message-ID: <9698f870-3e78-5ccb-b612-1eeef7d18f2c@sholland.org>
Date: Mon, 16 Jul 2018 17:23:04 -0500
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Hello,

On 07/16/18 03:50, Quan Zhou wrote:
> I've been using wg for a while without any problem, but today I wanted
> to try something with the namespace[1]. There's a difference in my
> settings, I already have a wg working without the netns. This or
> perhaps other factors results in a failure bringing up the interface:
> ``RTNETLINK answers: Address already in use.'' Details follow.
> 
> [1]: https://www.wireguard.com/netns/
> 
> Configuration:
> ==== SiteA to SiteC (working correctly):
> 
> ```bash
> ip link add dev wg0 type wireguard
> wg setconf wg0 /etc/wireguard/wg0.conf
> ip link set up dev wg0
> ip route add 192.168.<>.0/24 dev wg0
> ip route add 10.12.<>.0/24 dev wg0
> ```
> ==== SiteA to SiteB (Trouble bringing up iface on Site A):
> ```bash
> ip netns add sv0
> ip link add sv0en0 type veth peer ens3
> ip link add sv0wg0 type wireguard
> ip link set sv0en0 netns sv0
> ip link set sv0wg0 netns sv0

Here you're creating the WireGuard interface before moving it to the sv0
namespace. The underlying UDP socket used by WireGuard is created in the
original namespace, and is _not_ moved with the interface. If you're using the
same ListenPort on both interfaces, the sockets will conflict, as you can see in
dmesg. Either:
- Use different listen ports for the two WireGuard interfaces, or
- Create sv0wg0 in the sv0 namespace instead of moving it there after the fact.

> ip -n sv0 addr add <IP>/32 dev sv0en0
> ip -n sv0 route add default dev sv0en0
> ip -n sv0 link set up sv0en0
> ip netns exec sv0 wg setconf sv0wg0 ./sv0wg0.conf
> ip -n sv0 addr add <IP>/31 dev sv0wg0
> ip -n sv0 link set up sv0wg0
> ```
> # ip -n sv0 link set up sv0wg0
> RTNETLINK answers: Address already in use
> 
> ==== dmesg |grep wireguard
> ```
> [   16.051148] wireguard: loading out-of-tree module taints kernel.
> [   16.051390] wireguard: module verification failed: signature and/or
> required key missing - tainting kernel
> [   16.051880] wireguard: WireGuard 0.0.20180708 loaded. See
> www.wireguard.com for information.
> [   16.051881] wireguard: Copyright (C) 2015-2018 Jason A. Donenfeld
> <Jason@zx2c4.com>. All Rights Reserved.
> [  214.191712] wireguard: sv0wg0: Could not create IPv4 socket
> [  233.096882] wireguard: sv0wg0: Could not create IPv4 socket
> [  250.411586] wireguard: sv0wg0: Could not create IPv4 socket
> [  522.266844] wireguard: sv0wg0: Could not create IPv4 socket
> [  950.891264] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1004.031902] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1044.773710] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1053.273612] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1057.656802] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1312.781415] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1359.582271] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1370.719755] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1586.955734] wireguard: sv0wg0: Could not create IPv4 socket
> [ 1603.063851] wireguard: sv0wg0: Could not create IPv4 socket
> [ 2257.095367] wireguard: wg0: Could not create IPv4 socket
> [ 3631.242070] wireguard: sv0wg0: Could not create IPv4 socket
> ```
> ==== Workaround (not really)
> ```bash
> # ip link set down wg0
> # ip -n sv0 link set up sv0wg0
> # # >>> Works
> # ip link set up wg0
> # # >>> RTNETLINK answers: Address already in use
> # # >>> See entry [ 2257.095367] in the dmesg above
> ```
> 

Regards,
Samuel