Subject: Re: Comments on 2292bis (Adv. API)

From: Tim Hartrick <[email-masked]>
Date: Wed, 1 Sep 1999 09:24:43 -0700 (PDT)

Erik,

> 
> 
> > I would say that a non-zero sin6_scope_id overrides the IPV6_MULTICAST_IF
> > option and that the interface indices in the IPV6_PKTINFO and IPV6_NEXTHOP
> > options override the sin6_scope_id.
> 
> For IPV6_NEXTHOP are you talking about an ifindex in a sockaddr_dl?
> If so, will this override IPV6_PKTINFO or the other way around?
>

sockaddr_dl?  Where did that come from.  The IPV6_NEXTHOP options uses a
sockaddr_in6.  There is language in the document which implies that the
sockaddr in the option could be some other kind of sockaddr but that seems
like unnecessary flexibility/complexity.  It is IPV6_NEXTHOP and should only
apply to IPv6.  I don't think we should be defining some generic next hop
option and if we are then it should be called SO_NEXTHOP and all of the
permutations should be specified.  I know I don't want to go there.

As you note, the IPV6_PKTINFO and the IPV6_NEXTHOP can contain conflicting
information.  The choices of how to deal with these conflicts are myriad.

We could use the last interface specified.  We could fail the operation if
there is a conflict....  I would probably opt for the former.
 
> For IPV6_PKTINFO there might be a difference whether it is a sticky option
> or in ancillary data.
> 

I am not sure what you mean here.

tim
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From: Erik Nordmark <[email-masked]>
Date: Wed, 1 Sep 1999 20:11:43 -0700 (PDT)

> permutations should be specified.  I know I don't want to go there.

I somehow forgot that sockaddr_in6 has an ifindex. Sorry for my confusion.

> there is a conflict....  I would probably opt for the former.

Well, "last specified" isn't well defined when a single sendmsg can carry more
than once ifindex (sounds like 3 currently with sin6_scope_id in the 
destination, in IPV6_PKTINFO, and in sin6_scope_id in the nexthop).

> I am not sure what you mean here.

A possible choice would be
	IPV6_PKTINFO in acillary data overrides sin6_scope_id in the destination
but
	sin6_scope_id in the destination overrides a sticky IPV6_PKTINFO

I'm not saying that this makes sense - I'm just saying that when exploring
the precedence rules we need to think about possible differences
whether a pirce of information is used as a sticky option or
as ancillary data.

But - I have a few more older emails to go through (as I edit the
document for clarity - makes the process somewhat slow :-(

  Erik