Getting IPv6 route advertisements to work over WG

[netravnen at gmail.com]

Dear Roman,

When using multicast over WireGuard, would it not be more viable to use
an extra encapsulation layer to run multicast inside of?

I am specifically thinking of running either GRE or L2TPv3 over wgX.

Christoffer

From: Roman Mamedov
Sent: Mon, Aug 27, 2018, 14:14 +0200 (Romance Daylight Time)
Subject: Getting IPv6 route advertisements to work over WG

> Hello,
> 
> I am trying to get IPv6 link-local IPs and route advertisements to work over
> WG. The reason is not for the usual case of address autoconfiguration, but to
> use RA as a dynamic routing protocol of sorts, as it can distribute routes --
> or in case of WG (where routes need to be static in AllowedIPs), act as a
> keep-alive protocol.
> 
> Example use: a host can be connected to a network via a number of independent
> routers (and separate WG tunnel to each); in case one of the routers goes
> down, the route entry that it was sending via RA times out, so the host will
> automatically use the other one(s) to reach that network. It would look
> similar to this:
> 
> # ip -6 route
> ...
> fd00::/32 via fe80::be:a0ff:fe18:4aac dev wg1 proto ra metric 1024  expires 30sec pref medium
> fd00::/32 via fe80::e8:4fff:fe94:2d7f dev wg2 proto ra metric 1024  expires 119sec pref medium
> fd00::/32 via fe80::43:31ff:fec0:da97 dev wg3 proto ra metric 1024  expires 86360sec pref low
> ...
> 
> What works:
> 
>   * manually assigning link-local(LL) IPs on both sides of a WG tunnel
>     (fe80:[somethingrandom]/64 scope link);
>   * any normal communication over these LL IPs (assuming they are also present
>     in AllowedIPs);
>   * running RADVD with WG link as one of its interfaces;
>   * explicitly requesting and receiving a RA, via using 'rdisc6' while specifying the
>     other side's LL IP;
> 
> What doesn't:
> 
>   * it appears multicast not supported, so anything involving
>     multicast, as in automatically requesting RAs on the kernel side, or
>     manually with 'rdisc6' but without specifying peer's LL:
> 
>       # rdisc6 wg3
>       Soliciting ff02::2 (ff02::2) on wg3...
>       Sending ICMPv6 packet: Required key not available
> 
> I found discussion[1], but it is unclear what is the outcome. In any case, I
> would like to add my vote to please add some kind of multicast support, even
> if just as a dumb broadcast for now. It would work just fine for a lot of
> cases; don't know about others, but my WG networks tend to include at most 2-3
> hosts each (but there's a lot of independent networks).
> 
> [1] https://lists.zx2c4.com/pipermail/wireguard/2017-April/001177.html
> 

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