Re: I-D ACTION:draft-jabley-ipv6-rh0-is-evil-00.txt

On 10-May-2007, at 11:38, George V. Neville-Neil wrote:

> At Thu, 10 May 2007 09:50:01 -0400,
> Brian Haberman wrote:
>>> The sentence could be modified in :
>>>
>>> "Compliant IPv6 hosts and routers MUST NOT process RH0 in packets
>>>   addressed to them. Those packets MUST be dropped without further
>>>   processing. In particular, the value of the Segments Left field
>>>   MUST not be considered."
>>>
>>
>> This is much clearer and easier to implement.
>
> Though I am not a router vendor I am the person who has to handle this
> on FreeBSD.  I like the above sentence as well.

The above sentences far more closely resemble what I meant to write,  
compared to the text that actually appeared in the draft :-)

I note that KAME's response to this is similar, but it's not clear to  
me that it's precisely identical: a patched KAME implementation  
treats the type 0 routing header as an unknown routing header  
(according to <http://www.kame.net/newsletter/20070502/>). This  
suggests to me that a patched KAME implementation will process a  
datagram containing RH0, but that RH0 header(s) in the datagram will  
not be acted upon. I would welcome corrections to my feeble  
assumptions in this area (I have done no tests, nor read any source  
code to confirm).

A packet containing RH0 presumably is intended not to be processed on  
the system identified by the destination address field; if it was, no  
RH0 would be present. This suggests to me that "MUST drop" is the  
right thing, rather than "process as if RH0 was not there"; in  
addition, if we assume that today any packet with RH0 is likely to be  
malicious, any processing of a packet containing RH0 which has the  
potential to result in backscatter seems like it should properly be  
avoided.

Joe

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