Date: Mon, 24 Sep 2001 07:01:02 -0400 From: Joe Abley <jabley@automagic.org> To: Juha Saarinen <juha@saarinen.org> Cc: 'Andrew Reilly' <areilly@bigpond.net.au>, freebsd-stable@FreeBSD.ORG Subject: Re: 127/8 continued Message-ID: <20010924070102.I4205@buffoon.automagic.org> In-Reply-To: <00e001c144c8$c33bf900$0a01a8c0@den2> References: <20010924160936.A10863@gurney.reilly.home> <00e001c144c8$c33bf900$0a01a8c0@den2>
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On Mon, Sep 24, 2001 at 07:16:00PM +1200, Juha Saarinen wrote: > :: Those packets are _supposed_ to get back to this host. That's > :: what loopback is for. > > Yes, I think the RFCs make a point of this. I'm not sure what you mean by "the RFCs". In http://www.iana.org/assignments/ipv4-address-space, 127/8 is listed as "IANA Reserved". The text in RFC1700 is not relevant to this discussion, since RFC1700 is no longer the authoritative repository for numbers (see http://www.iana.org/numbers.html). RFC 1122, "Requirements for Internet Hosts -- Communication Layers" provides guidance for the interpretation of any address within 127/8 -- it says such addresses are for use as "internal host loopback addresses". RFC 1122 is STD 3, an Official Internet Protocol Standard, and hence is worth complying with. RFC 1122 does not state that "every possible address within 127/8 must be treated as though it is a configured loopback address", and to interpret it as such is bizarre and counter-intuitive. RFC1122 also says, in the same paragraph, "addresses of this form MUST NOT appear outside the host." Installing a null covering route for 127/8 with the blackhole bit set seems a good way of preventing addresses with a destination within 127/8 from being sent out on a non-loopback interface, without resorting to nasty hacks which make address handling on the loopback interface different to every other interface. It is also consistent with the robustness principle. route add 127.0.0.0 -netmask 255.0.0.0 -iface lo0 -blackhole But, whatever. This is hardly a monumental requirement worth bickering over. Joe To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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