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Date:      Fri, 22 Aug 1997 16:46:18 -0700
From:      Julian Elischer <julian@whistle.com>
To:        wollman@freebsd.org
Cc:        hackers@freebsd.org
Subject:   promblems with non IP protocols
Message-ID:  <33FE24CA.52BFA1D7@whistle.com>

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Garrett, 

I've been looking at the problem of address families for
which netmasks just "don't work".
(e.g. appletalk)

I have basically come to the conclusion (as I mentionned to you
before) that there needs to be a way for address families to 
specify some methods for handling their addresses. 
e.g.  how to decide it an address is on an interface or not.

There are a couple of 'style' questions though that I'd like 
your (and in fact any-one's) advise on.

1/ I prefer if it is a dynamic thing and 
not dependent on a "#ifdef NETATALK" in the kernel.
Is this reasonable? 
(I'd like to work towards loadable protocols)

2/ If it's loadable, and a pointer to a method, then WHERE is the 
method stored, so that it can be found? there are several options.

	i) An extra entry in the domain struct (along with 
	   dom_externalize() and similar things,
	   but there is no easy way to index this as there is no
		AF_XXX->protocol lookup array (I might be wrong)

	ii) add and entry to the ifaddr struct.
	    there is already the protocol dependent rtrequest.
	    adding a protocol dependent address handler 
	    (can do compares, and other operations, given the 
	    appropriate args) doesn't seem like too much of a leap.

	iii) An AF_XXX indexed array..
	     there is already such an array to look up the  appropriate 
	     routing table for a protocol..

I tend to think a hybrid might be acceptable..
e.g. add a pointer from the ifaddr to the domain and add a 
new pointer from the domain, to the address method.
for that matter, if we hung the routing tables from the domain,
then the current routing table index array
could be used to find the domain (and hence the routing info),
when indexed by the AF_XXX entry, and get a convenient place to
hang a number of these things.

what are your thoughts?
who else would you suggest polling?
have an address for Rich Stevens?
kieth Skower? 
Mike karels?
etc?



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