Fwd: Re: wg-quick broken by iproute2 update

[Silvan Nagl]

-------- Forwarded Message --------
Subject: 	Re: wg-quick broken by iproute2 update
Date: 	Thu, 28 Jun 2018 11:53:59 +0200
From: 	Silvan Nagl <mail at 53c70r.de>
To: 	stunnel at attglobal.net



Hi,

since i had to debug this problem already i can tell you it is not
iproute2 causing the problem.
The main problem is that the current standard kernel of CentOS simple
does not support the handling of "suppress_prefixlength".
Iproute2 supports it since it does not return any error while adding so
it had to be the kernel causing problems.
In essence Red Hats official answer was "It isn't a bug, RHEL7 simple
does not support it".
If you sill want to fix your problem just upgrade your kernel to
long-term or mainline.

Regards,
Silvan

On 06/28/2018 04:47 AM, Eddie wrote:
> Hi,
>
> I just updated both a RHEL and a CentOS system from 7 -> 7.5. 
> Following this, when running wg-quick, the routing tables are not 
> updated correctly.  Both systems are running 
> iproute.x86_64-4.11.0-14.el7, but from different repositories and are 
> definitely different builds as they install to different sbin libraries.
>
> Here's what I'm seeing:
>
> [eddieath at oc8361880017 ~]$ sudo ip rule list
> 0:    from all lookup local
> 32766:    from all lookup main
> 32767:    from all lookup default
> [eddieath at oc8361880017 ~]$
> [eddieath at oc8361880017 ~]$ sudo wg-quick up wg0
> [#] ip link add wg0 type wireguard
> [#] wg setconf wg0 /dev/fd/63
> [#] ip address add 192.168.0.11/24 dev wg0
> [#] ip link set mtu 1420 dev wg0
> [#] ip link set wg0 up
> [#] ip -4 route add 0.0.0.0/0 dev wg0 table 51820
> [#] ip -4 rule add not fwmark 51820 table 51820
> [#] ip -4 rule add table main suppress_prefixlength 0
> [eddieath at oc8361880017 ~]$
> [eddieath at oc8361880017 ~]$ sudo ip rule list
> 0:    from all lookup local
> 32764:    from all lookup main
> 32765:    not from all fwmark 0xca6c lookup 51820
> 32766:    from all lookup main
> 32767:    from all lookup default
> [eddieath at oc8361880017 ~]$
>
> Note the "suppress_prefixlength 0" has been dropped, which really 
> breaks the routing with a "normal" main ahead of table 51820. 
> Following this, when running the "down", the duplicated table is not 
> removed, as there is no match searching for "suppress_prefixlength 0":
>
> [eddieath at oc8361880017 ~]$ sudo wg-quick down wg0
> [#] wg showconf wg0
> sync: ignoring all arguments
> [#] ip -4 rule delete table 51820
> [#] ip link delete dev wg0
> [eddieath at oc8361880017 ~]$ sudo ip rule list
> 0:    from all lookup local
> 32764:    from all lookup main
> 32766:    from all lookup main
> 32767:    from all lookup default
> [eddieath at oc8361880017 ~]$
>
> I've confirmed this on both systems and also that the behaviour is 
> purely within ip, and not anything that wg-quick is doing:
>
> [eddieath at oc8361880017 ~]$ sudo ip rule list
> 0:    from all lookup local
> 32766:    from all lookup main
> 32767:    from all lookup default
> [eddieath at oc8361880017 ~]$ sudo ip -4 rule add table main 
> suppress_prefixlength 0
> [eddieath at oc8361880017 ~]$ sudo ip rule list
> 0:    from all lookup local
> 32765:    from all lookup main
> 32766:    from all lookup main
> 32767:    from all lookup default
> [eddieath at oc8361880017 ~]$
>
> Cheers.
>
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