Re: Does RFC9000 allow endpoints to reuse CIDs when NAT rebinding happens?

[Eric Kinnear <[e-mail]>]

That said, if the server notices that the client is coming from a different address and using the same destination CID, which would not be allowed if the client knew that it was using a different network path, it’s nice if it does change CID. This provides a signal to a client that a NAT rebinding may have occurred, and the client might choose to take action on that in some way.

Since you’re allowed to change CID at any time on the same path, there’s no need for additional text that explicitly allows this, but the most straightforward implementation that just says “yup, you’re on a different remote address, I’ll use a different CID” and doesn’t check whether the remote peer rotated CID is likely the best answer.

Thanks,
Eric


> On Sep 25, 2023, at 8:37 PM, Willy Tarreau <[e-mail]> wrote:
> 
> On Tue, Sep 26, 2023 at 11:04:40AM +0800, "???(Personal)" wrote:
>> Is it allowed for a server to reuse the current CID when it notices a NAT
>> rebinding? I wonder if the text ("...., in which case it MAY continue to use
>> the current connection ID with the new remote address while still sending
>> from the same local address.") indicates that the server can reuse the
>> current CID?
> 
> If the spec says "MAY", then yes, it's allowed to.
> 
> Willy
>