Date: Fri, 29 Jun 2001 09:28:54 -0700 From: "Kevin Oberman" <oberman@es.net> To: JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= <jinmei@isl.rdc.toshiba.co.jp> Cc: freebsd-net@FreeBSD.ORG Subject: Re: Odd IPv6 behavior when not connected to IPv6 net Message-ID: <200106291628.f5TGSsc13240@ptavv.es.net> In-Reply-To: Your message of "Fri, 29 Jun 2001 11:00:18 %2B0900." <y7v1yo4jb9p.wl@condor2.jinmei.org>
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> Date: Fri, 29 Jun 2001 11:00:18 +0900 > From: JINMEI Tatuya / =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= <jinmei@isl.rdc.toshiba.co.jp> > Sender: owner-freebsd-net@FreeBSD.ORG > > >>>>> On Fri, 29 Jun 2001 06:12:28 +0900 (JST), > >>>>> Hajimu UMEMOTO <ume@mahoroba.org> said: > > oberman> I agree, but I have made no deliberate changes. I just install FreeBSD > oberman> with ipv6_enable="YES" in rc.config. > oberman> Internet6: > oberman> Destination Gateway Flags Netif Expire > oberman> :: localhost UGRSc lo0 => > oberman> default fe80::1%lo0 Uc lo0 > > > Why are you set ipv6_enable to YES while you are not using IPv6? :-) > > I just could reproduce your problem. When no RA is available, default > > route is wrongly installed by `ndp -I'. > > Please set ipv6_default_interface to NO in your rc.conf. Current its > > default setting is meaningless in most cases and it is harmful. I'll > > change default of ipv6_default_interface to NO. > > Please let me explain the rationale. The notion of > "ipv6_default_interface" is introduced mainly for conformance to the > following part of RFC 2461: > > Next-hop determination for a given unicast destination operates as > follows. The sender performs a longest prefix match against the > Prefix List to determine whether the packet's destination is on- or > off-link. If the destination is on-link, the next-hop address is the > same as the packet's destination address. Otherwise, the sender > selects a router from the Default Router List (following the rules > described in Section 6.3.6). If the Default Router List is empty, <--- > the sender assumes that the destination is on-link. <--- > > That is, if we do not have any default router (hear from RA), we > should regard all IPv6 prefixes as on-link. To implement this trick, > we use the "default interface", and install the default route as an > interface direct route to the interface. I think the basic idea in the RFC may be reasonable. It only breaks when the link selected is loopback. Had the stack tried to connect to a physical link, this would have worked as intended, but loopback will always be the wrong answer if it is the link used. > Thus, for the moment, I agree that we should turn the default > interface off by default. For a longer term solution, we might have > to consider a better source address selection algorithm, > e.g. described in draft-ietf-ipngwg-default-addr-select-04.txt. Then > IPv4 would be preferred in this case. This is certainly reasonable, too. But the step of not allowing the lo interface to qualify as the link for the default route seems like something that should be done as well. Of course, there may be some reason to want default to point at lo, but I can't think of a good one. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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