* Do DNS queries for both A and AAAA simultaneously
We implement a basic version of RFC8305 (happy eyeballs) to establish
the connection afterwards.
* Try to connect to UDP sockets simultaneously
This change adds a `port_mapping` option to the `ReverseTunnel` definition in the (YAML) restriction file.
It maps ports on the server side from X to Y (X:Y). Where X is the originally requested port by the client and Y is the port which will be used to listen on server-side.
For example with `10001:8080` configured and a client which connects using `-R tcp://10001:localhost:80` the server will listen on port 8080 instead of 10001. The originally requested ports (NOT the mapped ports) still needs to be allowed via the `ports` directive.
This is for example useful when dealing with lots of clients and you don't want to coordinate port use on all the clients but centrally on the server.
This change marks combining the yaml restrictions file together with arguments such as `--restrict-http-upgrade-path-prefix` as conflicting in clap. Since wstunnel will only use the yaml restrictions file when it is supplied and ignore the other arguments. This change makes this more obvious for users (since wstunnel will exit with an error).
The reason for still allowing the client `--http-upgrade-path-prefix` is that one could be using a proxy server in front of wstunnel which does mTLS. This is a pretty specific corner case though. A warning was added so it's clear to users that this will only work in specific scenarios.
This change makes the server verify the client's path prefix matches the common name (CN) in the certificate the client presented when mTLS is used. This makes it impossible for the client to spoof the path prefix specified in the `restrictions.yaml` file.
