netdev - Re: [PATCH] make TLLAO option for NA packets configurable

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Date:	Thu, 1 Oct 2009 19:43:44 +0300
From:	Cosmin Ratiu <cratiu@...acom.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	netdev@...r.kernel.org, Octavian Purdila <opurdila@...acom.com>
Subject: Re: [PATCH] make TLLAO option for NA packets configurable

On Thursday 01 October 2009 19:21:00 Stephen Hemminger wrote:
> On Thu, 1 Oct 2009 19:16:40 +0300
>
> Cosmin Ratiu <cratiu@...acom.com> wrote:
> > Hello,
> >
> > This is a patch that adds a sysctl to control the sending of the Target
> > Link Layer Address Option (TLLAO) with Neighbor Advertisements responding
> > to unicast NS. The patch was made for kernel 2.6.7 (yes it is ancient),
> > but the code is similar with the current kernel and I can rework it if
> > you want it in.
> >
> > RFC 2461, page 24 suggests that this option should be included with NAs
> > to avoid a race with the sender clearing its cache after sending an
> > unicast NS, but before receiving a NA.
> >
> > It seems there are some Juniper routers (MX series) that expect this
> > option to be included with all NAs.
> >
> > Another solution is to always send this option, as it has little
> > overhead.
> >
> > Please let me know what you think,
> > Cosmin.
> >
> > Signed-off-by: Cosmin Ratiu <cratiu@...acom.com>
> > --- //packages/linux_2.6.7/main/src/include/linux/sysctl.h
> > +++ /home/z/w1/packages/linux_2.6.7/main/src/include/linux/sysctl.h
> > @@ -444,6 +444,7 @@
> >         NET_IPV6_IP6FRAG_TIME=23,
> >         NET_IPV6_IP6FRAG_SECRET_INTERVAL=24,
> >         NET_IPV6_MLD_MAX_MSF=25,
> > +       NET_IPV6_NDISC_FORCE_TLLAO=26,
>
> Since numbered sysctl values are deprecated, can you use CTL_UNNUMBERED
> to avoid having to add yet another value?

Of course, but that is a detail.
If you decide on the sysctl solution, I'll do it.
If you decide on making this the default behavior, it's even better.

Cosmin.
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