Hemant Singh (shemant) wrote: > Please see in line below with "<hs>" > > -----Original Message----- > From: Ralph Droms (rdroms) > Sent: Friday, June 29, 2007 10:26 AM > To: JINMEI Tatuya / ???? > Cc: IETF Mailing List IPv6; Wes Beebee (wbeebee); Hemant Singh (shemant) > Subject: Re: draft-wbeebee-nd-implementation-pitfalls-00 with urgent > changessuggested to 2462bis-08 > > > On Jun 28, 2007, at Jun 28, 2007,1:14 AM, JINMEI Tatuya / 神明達哉 > wrote: > >> At Wed, 27 Jun 2007 14:27:37 -0400, >> Ralph Droms <[EMAIL PROTECTED]> wrote: >> >>> One bug that may or may not be common is to make assumptions about >>> the prefixes on a link based on addresses assigned to an interface. >>> I can imagine (and I believe we've actually made a real sighting of >>> this scenario) that an IPv6 implementor might extrapolate IPv4 >>> conventions and extract the /64 prefix from an assigned address >>> (either SLAAC, DHCP or manual config), and add a route to the host >>> table indicating that the prefix is on-link, regardless of whether >>> the prefix is advertised as "on-link" in an RA. >> [...] >> >> If the system administrator manually configures an IPv6 address with a >> prefix length smaller than 128, the kernel will assume that the >> corresponding prefix is on-link. But I believe this should be >> reasonable. >> >> JINMEI, Tatuya >> Communication Platform Lab. >> Corporate R&D Center, Toshiba Corp. >> [EMAIL PROTECTED] > > I see where draft-wbeebee-nd-implementation-pitfalls also mentions manual > configuration as a special case: > > 2. The RA and ICMPv6 Redirects from the default router are the only > sources of information for on-link determination. DHCPv6 or any > other configuration on the host MUST NOT be used for on-link > determination. Manual configuration of a host introduces its own > set of security considerations and is beyond the scope of this > document. > > Is there some reason to believe the information about on-link prefixes should > be implicitly overridden in the case of manual address assignment? I can > understand explicitly overriding information from RAs by manually configuring > the on-link information as a separate step from manual address assignment. > But it seems to me that assuming the prefix from a manually configured > address is on- link might cause unexpected loss of connectivity if the prefix > does require off-link delivery through the router.
At least as a sysadmin/user I would find it confusing if the prefix length I configured would not be used for on-link determination. I think it's more bad than good to try to separate the two. I'm happy the way it currently is on the systems I've seen. > > <hs> If the host has been manually configured for IPv6 address where the host > was also configured for prefix and prefix length, then what's on-link for > this host can be determined by host. But what if manual configuration > configured an IPv6 address and maybe, also the prefix, but forgot to > configure prefix length. Then this manual configuration has no means to > determine what's on-link for a destination based on the data from manual > configuration. I have host not assuming a default prefix length yet. The RA > has been explicitly ignored. So not this host has no choice but to send > non-link-local traffic to the default router. Specifying manual configuration > behavior and its interaction with RA is a can of worms that will take time to > clear up. Can you manually configure prefix on a host without also specifying prefix length? Stig > > Hemant > > - Ralph > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
