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.
- Ralph
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