# What is this crate used for?

At the time of writing, TLS negotiation for ffx.

# Are there any use restrictions? i.e. only for development hosts

No.

# What differs from upstream?

This fork of rustls 0.19.1 includes patches to:

 * Enable RFC8446 C.4: Client Tracking Prevention
 * Fix a bug in RFC8446 D.4: Middlebox Compatibility Mode, in which concurrent connections may race,
   resulting in updating the session ticket used, breaking the compatibility mode.
 * Renames the cargo version to 0.17.0 to be compatible with our current
   versions of hyper-rustls, rustls-native-certs, and tokio-rustls.

# Are there any restrictions to how it should be rolled?

 * We should not unfork until [the upstream bug for C.4](https://github.com/ctz/rustls/issues/466) is
   resolved.

# Is there anything else which makes this dependency "special"?

No.