BGP strict bind socket error

[Alexander Zubkov]

On Thu, Jan 23, 2020 at 5:21 PM Ondrej Zajicek <santiago at crfreenet.org> wrote:
>
> On Wed, Jan 15, 2020 at 01:57:19AM +0100, Alexander Zubkov wrote:
> > Hi,
> >
> > Check the attached patches. The first adds option to sockets to use
> > nonlocal bind (IP_FREEBIND in Linux) and the second adds bgp option to
> > use such sockets ("nonlocal bind yes|no"). Some additional thoughts:
> > - probably the option could be implemented for any protocol, not only for bgp
> > ...
> > - it can be also considered to enable nonlocal bind for all bgp
> > unconditionally, at least I see no obvious problems yet
>
> Hi
>
> Is there a reason for such option? Is there a downside of using it always?

If I remember right, when address is not available during bind, in
strict bind mode bird logs en error and puts protocol down. It is
inconvenient when one uses VRRP, for example, with migrating address.
Or there could be some problems during applying some configuration
changes to the interfaces in the system. We use this socket option
with VRRP and also we have interfaces without ip addresses configured
yet for some reason.
I do not know if using it always-on is a good idea or not. We made it
always-on in our setup and are just happy with it. But I'm not sure if
it does not break something somewhere. It will make at least bird's
behaviour different on different systems with the same config and that
may be confusing. On the other hand, the extra option to put in config
may be unreasonable payment.
I also not tested how it will behave if ip address migrates from one
interface to the other in the system. If it ties to the interfaces
somehow and because of this option does not mention the change, that
could be a problem.

>
> One minor nitpick is that sysdep/unix/io.c should not use non-portable
> syscalls/sockopts directly, they should be defined as functions in
> sysdep/X/sysio.h (with implementations for Linux and BSD) and such
> function called from sysdep/unix/io.c code.

Probably you are right, it might be somewhere there if it would end
into the vanilla bird.

>
> --
> Elen sila lumenn' omentielvo
>
> Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
> OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
> "To err is human -- to blame it on a computer is even more so."