Strict Bind usability

[Sebastian Hahn]

Hi Ondrej,

> On 6. Feb 2024, at 19:33, Ondrej Zajicek <santiago at crfreenet.org> wrote:
>> 
>> I would like to use dynamic bgp (using a range for neighbour) with
>> auto-configured LL IPv6 adresses. This doesn't work, of course, if I need
>> to statically configure the source address, which I am forced to with the
>> strict bind option. I am wondering, is this restriction really needed?
> 
> Hi
> 
> You are right, this is something that could be easily changed. Will look at it.

That would be awesome :)

>> In addition, it would be great if a strict bind option could be added for the babel protocol.
> 
> Babel (and OSPF, RIP) already uses one socket per interface. Such socket
> is not bound to specific IP address using bind(), but is bound to the
> specific interface using setsockopt(SO_BINDTODEVICE), at least in Linux.
> 
> We cannot use bind() with local IP address for multicast sockets, as they
> would reject multicast packets (as they have different dst address as one
> the socket is bound).
> 
> Anyway, it should not be necessary. AFAIK, setups that require strict
> bind in BGP should work out of the box in Babel. Or what specific setup
> does not work for you?

Oh, I think I was confused by the output of netstat. Using ss instead, I
can see that bird correctly binds to just the devices specified in the
configuration. I had previously assumed it was binding to all interfaces.
Very sorry for this basic mistake.

Thanks!
Sebastian