feat: Host-based proxy

[JyJyJcr]

Abstruct

It is a typical situation that there are multiple servers in private network and only one proxy server is accessible from public network(or the Internet).
TLS enables to deal with the situation using SNI, and is included in QUIC protocol.
In this PR, Host-based routing is implemented using SNI.

Usage

1. List up the mapping of host names to socketaddrs in conf file.
2. Launch server specifying the conf file path.
3. Run client using domain(host) name in URL.

Example:

• ./quicssh-rs.toml

[proxy]
"xxx.example.net"="192.168.0.10:22"
"yyy.example.net"="192.168.0.10:2222"
"zzz.example.net"="192.168.0.20:22"
default="192.168.0.30:22"

• launch server

quicssh-rs server -F ./quicssh-rs.toml

• run client

quicssh-rs client quic://xxx.example.net # -> 192.168.0.10:22
quicssh-rs client quic://yyy.example.net # -> 192.168.0.10:2222
quicssh-rs client quic://zzz.example.net # -> 192.168.0.20:22
quicssh-rs client quic://<raw ip, or other domain name> # -> 192.168.0.30:22

[oowl]

Thanks!