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Date:      Thu, 30 Nov 2000 15:00:29 -0500 (EST)
From:      Dominick LaTrappe <seraf@2600.COM>
To:        itojun@iijlab.net
Cc:        freebsd-net@freebsd.org, Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>, Gerhard Sittig <Gerhard.Sittig@gmx.net>
Subject:   Re: filtering ipsec traffic (fwd) 
Message-ID:  <Pine.NEB.4.21.0011301440230.8590-100000@phalse.2600.com>
In-Reply-To: <26650.975598272@coconut.itojun.org>

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On Fri, 1 Dec 2000 itojun@iijlab.net wrote:
> from IPv6 point of view (yes, I'm IPv6 centric!) we cannot add extra
> interface like tun0.  IPv6 has scoped address, and if we add extra
> interface in IP stack we will change the address semantics.

I take this to mean that in KAME an IPv6 address's scope cannot span
multiple interfaces, which is in itself a big limitation that will prevent
a lot of code from being IPv6-enabled.

Given that, I think a sysctl like net.inet.ipsec.filter would be a good
solution -- to cause a pass over the filter rules to be called from inside
KAME, when the packet is in its non-IPsec state.  Address scope will be
preserved because no additional interface is required.  If the rules are
written efficiently (with groups or skipto's to distinguish between IPsec
and non-IPsec packets), the overhead will be little -- certainly no more
than filtering built-into other IPsec implementations.

Alternatively, this could be introduced as an SPD flag.

So far, just one limitation comes to mind, which is that the packet
filters cannot discriminate between a naturally non-IPsec packet, and a
non-IPsec packet which 'was' or 'will be' an IPsec one.  I don't think
this is a big problem though.

	||| Dominick




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