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List:       bird-users
Subject:    Re: [PATCH 1/7] Babel: Make sure intervals don't overflow.
From:       Toke_Høiland-Jørgensen <toke () toke ! dk>
Date:       2016-07-20 12:02:24
Message-ID: 87bn1splf3.fsf () toke ! dk
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Ondrej Zajicek <santiago@crfreenet.org> writes:

> On Tue, Jul 19, 2016 at 06:09:41PM +0200, Toke Høiland-Jørgensen wrote:
> > Ondrej Zajicek <santiago@crfreenet.org> writes:
> > 
> > > On Mon, May 02, 2016 at 07:07:49PM +0200, Toke Høiland-Jørgensen wrote:
> > > > Intervals are carried as 16-bit centisecond values, but kept internally
> > > > in 16-bit second values, which causes a potential for overflow. This
> > > > adds some checks to make sure this doesn't happen.
> > > > 
> > > > +  /* make sure we don't overflow the 16-bit centisec fields */
> > > > if (!BABEL_IFACE->update_interval)
> > > > -    BABEL_IFACE->update_interval = \
> > > >                 BABEL_IFACE->hello_interval*BABEL_UPDATE_INTERVAL_FACTOR;
> > > > -  BABEL_IFACE->ihu_interval = \
> > > > BABEL_IFACE->hello_interval*BABEL_IHU_INTERVAL_FACTOR; +    \
> > > > BABEL_IFACE->update_interval = \
> > > > MIN_(BABEL_IFACE->hello_interval*BABEL_UPDATE_INTERVAL_FACTOR, \
> > > > BABEL_MAX_INTERVAL); +  BABEL_IFACE->ihu_interval = \
> > > > MIN_(BABEL_IFACE->hello_interval*BABEL_IHU_INTERVAL_FACTOR, \
> > > > BABEL_MAX_INTERVAL);
> > > 
> > > This is not completely correct, because IHU interval is not independent
> > > of hello_interval in this implementation - IHUs are sent for each
> > > BABEL_IHU_INTERVAL_FACTOR hellos even if ihu_interval is limited by this.
> > 
> > Yeah, you're right. Hmm, guess it doesn't really make sense to have the
> > IHU interval configurable by itself, then?
> 
> Probably not. But it makes sense to have configurable IHU factor
> (different for wired and wireless networks). And if hello*factor is too
> large, then just use smaller factor.

Right, makes sense. I'll write that up and submit another patch :)

-Toke


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