[PATCH v2] Babel: fix seqno wrapping on seqno request

[Ondrej Zajicek]

Thanks, merged.

On Mon, Dec 09, 2024 at 10:51:28AM +0100, Toke Høiland-Jørgensen via Bird-users wrote:
> Fabian Bläse <fabian at blaese.de> writes:
> 
> > The Babel seqno wraps around when reaching its maximum value
> > (UINT16_MAX). When comparing seqnos, this has to be taken into account.
> > Therefore, plain number comparisons do not work.
> >
> > In a previous attempt to fix the wrapping behavior, one particular
> > comparison was missed. This causes the seqno of originated babel routes
> > to not wrap, but remain at UINT16_MAX indefinitely, resulting in slow
> > route propagation on topology changes.
> >
> > Make use of the previously introduced gt_mod64k macro to compare seqnos
> > correctly.
> >
> > Fixes: 3e7e4a71868bc519aacc0eb785471b46fc345a5c
> >
> > Signed-off-by: Fabian Bläse <fabian at blaese.de>
> >
> > ---
> > v2: fix syntax error
> >
> >  proto/babel/babel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/proto/babel/babel.c b/proto/babel/babel.c
> > index fe5c0599..209492f0 100644
> > --- a/proto/babel/babel.c
> > +++ b/proto/babel/babel.c
> > @@ -1015,7 +1015,7 @@ babel_send_update_(struct babel_iface *ifa, btime changed, struct fib *rtable)
> >  
> >      /* Our own seqno might have changed, in which case we update the routes we
> >         originate. */
> > -    if ((e->router_id == p->router_id) && (e->seqno < p->update_seqno))
> > +    if ((e->router_id == p->router_id) && (gt_mod64k(p->update_seqno, e->seqno)))
> 
> I'd drop the extra parentheses around gt_mod64k(), but otherwise LGTM!
> 
> Reviewed-by: Toke Høiland-Jørgensen <toke at toke.dk>

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
"To err is human -- to blame it on a computer is even more so."