IPv6 Type 0 Routing Header issues

Jun-ichiro itojun Hagino itojun at itojun.org
Tue Apr 24 00:25:27 CEST 2007

	pekka, long time no see!

> Speaking of which, during the last couple of months some folks appear 
> to have been testing these.  Specifically, our egress source spoofing 
> filters block some routing header packets between 
> 2001:AD0:301:1002::/64 (DT-IPV6-EE-TLN-VS1) and 2001:730:5::/48 
> (NEXTGEN-LAB).  I wonder what those folks are trying to do, maybe test 
> ingress filters or map topology using 'roundabout' traceroute..

	the issue is rather horrifying, it could be the doomsday of the entire

	RFC1883 had upper limit in # of hops, 23 (strict/loose bitmap).
	when Deering removed the field, he forgot to put the upper limit.

	also, there's no limit in number of routing header present on a packet.

	now, you will be able to compute how many source-routing hops a packet
	(try MTU 1280 and 9000).  try to compute maximum number of hops.

	to prevent panic i'll leave it as an exercise for readers, but
	it's mind-blowing.  try it.

	if you understood the risk, feel free to contact core at kame.net.
	(but due to time difference many are in bed now)

	pekkas, call me at +81 90 9158 7979 or +81 3 3490 9225.
	(i slept only 4 hours since last Friday due to this issue, so keep


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