Code change:
9. <ins> Extensions to CONNECT-IP can define behavior changes to this mechanism.  Such extensions SHOULD define new capsule types to exchange configuration information if needed.  It is RECOMMENDED for extensions that modify addressing to specify that their extension capsules be sent before the ADDRESS_ASSIGN capsule and that they do not take effect until the ADDRESS_ASSIGN capsule is parsed.  This allows modifications to address assignement to operate atomically. Similarly, extensions that modify routing SHOULD behave similarly with regards to the ROUTE_ADVERTISEMENT capsule. 10. </ins> There are significant risks in allowing arbitrary clients to establish a tunnel to arbitrary servers, as that could allow bad actors to send traffic and have it attributed to the proxy.  Proxies

Related discussion:
text: Then getting ICMP for another IP address then the one you already have UDP for is mostly useless if you intended to use the ICMP messages for hints when things fails for you UDP based protocol. I would note that for an endpoint liking to do P2P NAT traversal stuff getting an IP address rather than using Connect-UDP does make sense as it ensure the client has control. It enables the IP address for its UDP traffic to be Endpoint-Independent Mapping (RFC4787). This might be niche usages but I would like to avoid creating artificial barriers that makes things impossible or at least hard to realise.
Thanks, this makes sense. Should we suggest that clients bundle the ADDRESS_REQUEST in the same packet as the HTTP headers and suggest that servers check for those before responding?
I am still worried that this creates issues as your request may not fit in a single packet to begin with. My solution would be to actually move the address request part into the HTTP request itself as header field. That would ensure an atomic operation and no risk for errors.
Magnus, is your proposal to require, or to allow as an option, for the address request to be moved into the HTTP request? Why not bundle the capsules over a reliable delivery mechanism instead?
I first of all want to ensure that you can do a request that ensures that for those cases when it is necessary to interpret the Connect-IP request in the context of desired IP address it can done. Without uncertainties or requiring to have wait time to see if there are capsules incoming. So I think primarily allow as an option. I think a question back to your usages, do you have cases where one would need additional capsules to correctly interpret the option. Should we look for an other solution than the one I proposed to better cover the necessary functionality?
I want to be able to continue to do ADDRESS_ASSIGN capsules during the lifetime of the connection to support e.g., IPv6 Privacy extensions but without having to delegate the entire subnet. So I don't want to move to header-only.
I think NAME is describing something similar to the / capsules that we had in the original Google . The only difference is that we would add an HTTP header to say "start off in atomic mode and wait for atomic end before sending addresses and such". While I think this does sound useful, does it need to be in the core spec or could it be an extension?