Daniel McCarney

Support for this was added to `main` as [`CommonState::negotiated_key_exchange_group`](https://rustls.github.io/rustls/prerelease/struct.CommonState.html#method.negotiated_key_exchange_group).

This is now available as part of [0.23.11](https://github.com/rustls/rustls/releases/tag/v/0.23.11).

Note due to the `NamedGroup::Unknown` variant (which, as discussed in https://github.com/rustls/rustls/pull/1845 should probably be named `NamedGroup::Other`) the consumer might have to do a bit of legwork with the result from...

> Shower thought: we could perhaps return Option We can now implement bogo -expect-curve-id, -on-initial-expect-curve-id, and -on-resume-expect-curve-id options on top of this (either in this PR, or a later one)....

> Some checks haven’t completed yet :cloud_with_lightning_and_rain: Looks like [bad weather](https://www.githubstatus.com/incidents/9vwllhs2w1kj): > Actions runs triggered by pull requests are experiencing start delays.

I think the TLS 1.2 code paths are still setting the common state KX too soon. I will take another look at that & test coverage shortly.

I gave this branch some more thought and reworked how it was implemented (sorry to push changes after positive reviews!). The new version removes the `ClientHelloDetails` field addition, removes some...

> We can now implement bogo -expect-curve-id, -on-initial-expect-curve-id, and -on-resume-expect-curve-id options on top of this (either in this PR, or a later one). Unfortunately the API we're exposing doesn't make...

> Why not? Because key exchange wasn't negotiated/performed. Do you have a non-bogo use-case in mind that would benefit from the information? > Does the cipher suite getter return None...

> This caveat is not documented -- probably want to fix that? Agreed, I will fix and also add a pointer to the fn that returns whether it was a...