[Mip6] [issue73] v4 mapped address in IPv6 header

New submission from Koshiro MITSUYA <mitsuya@sfc.wide.ad.jp>:

the IPv4 mapped address has a special meaning by RFC
2553 API.  It is not preferable to use the mapped address in IPv6
headers (See the following the drafts)
	draft-itojun-v6ops-v4mapped-harmful
	draft-cmetz-v6ops-v4mapped-api-harmful

In our code based on KAME, the IPv6 implementation discard a IPv6
header which has the v4 mapped address for sanity at ip6_input() and
ip6_rthadr2().  We also need to add the mapped address in an address
list (the list of all addresses which the node has) to receive the
header.  This is somehow uncomfortable because the mapped address is
actually not routable.

>From Hesham:
=> No one suggested that it should/would be routable. It's simply
used to keep the packet format. There is no routing based on this 
information. 

>From Koshiro:
=> I am not sure whether it's just an implementation issues.  But putting
the mapped address in the address list in order to process the DSMIP
IPv6 header means the mapped address may be chosen as a source address
even the address is actually not routable.  To avoid this, we need
e.g. an additional flag to distinguish the mapped address from others.
I think some implementers will not accept this.

The above is not only the reason again the mapped address in the IPv6
header.  Please refer the draft-*-harmful.  So, my idea is to put HoA
in IPv6 header and kind of IPv4 CoA option to idicate it's IPv4 CoA.

BTW, if you just want to keep the packer format, I think it's better
to use compatible address, or 6to4 address, or newly-defined address
for this purpose.

----------
category: Technical
draft: draft-ietf-mip6-nemo-v4traversal
messages: 237
nosy: mitsuya
priority: Should fix
status: No discussion
title: v4 mapped address in IPv6 header

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