Subject: Re: [BEHAVE] ICMP extensions

From: Xing Li <[email-masked]>
Date: Wed, 04 Nov 2009 10:54:51 +0800

marcelo bagnulo braun 写道:
> Hi,
>
> I am trying to understand how to handle ICMP extensions.
>
> In the current draft, the text covering extensions is:
>
> 2.3. Translating ICMPv4 Headers into ICMPv6 Headers
>
> ...
>
> ICMP Error Payload The [RFC4884] length field should be
> updated to reflect the changed length of the datagram.
> There are two cases for the length field modifications.
> That the translated packet is created from scratch and the
> length field never is filled in. Then an ICMP extension
> will result in that it will be treated as part of the
> original datagram field. If the IP payload is copied and
> then modified then the length field will be unmodified while
> the original datagram field will become longer by the
> address translation from v4->v6. Thus cutting off the end
> of the original datagram field for ICMP extension aware
> receivers. information.
>
> However, i have not found text covering the ICMP extension translation 
> in the other direction and afaiu, icmpv6 messages can also contain 
> extension, correct?

Yes. In the current version, we did not present the details. The reason 
is that from v6 -> v4, the original datagram field will become short.
We can insert the details in the next version.

ICMP Error Payload The [RFC4884] length field should be
updated to reflect the changed length of the datagram.
There are two cases for the length field modifications.
That the translated packet is created from scratch and the
length field never is filled in. Then an ICMP extension
will result in that it will be treated as part of the
original datagram field. If the IP payload is copied and
then modified then the length field will be unmodified while
the original datagram field will become shorter by the
address translation from v6->v4.

Any comments?

Regards,

xing
>
> Regards, marcelo
>
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