Introduce Wireguard support to bird

[Janne Heß]

On 6/8/19 12:18 AM, Toke Høiland-Jørgensen wrote:
> Janne Heß <janne at hess.ooo> writes:
> 
>> Hey everyone,
>>
>> as advertised, I have completed the Wireguard support.
>> You might see that I am not really a C expert, but I hope the code is good enough.
>> If you need me to change anything or have additional questions, just
>> let me know.
> 
> Hi Janne
> 
> Awesome that you have taken the time to implement this!
> 
> I'll let the Bird maintainers comment on the approach of embedding the
> wireguard netlink library; but I have two other concerns:
> 
> - As far as I can tell there's nothing preventing Bird from removing
>    AllowedIPs that it did not itself install from an interface, right?
> 
> - The algorithm is basically O(P*M*N) for inserting N routes on an
>    interface with P peers that each have M existing AllowedIPs. That is
>    not going to scale very far :/
> 
> -Toke
> 

Hi Toke,

thanks for your review.

Your first observation is correct. Due to differences in semantics, this 
cannot be implemented in the same way it is implemented in the KRT 
protocol because AllowedIPs don't have a notion of the proto field.

Addressing your second point, the WireGuard netlink interface and 
library only offer and understand the peers and allowed IPs as a linked 
list.
As we only get each route seperately, we cannot process multiple routes 
in one run. We're open to suggestions and patches.

Regards
Janne