feat: intercept and forward to our own destination

[daiyam]

This PR allows to intercept and to forward to our own destination.

It has been used in production in the project https://github.com/jeanp413/open-remote-ssh/ (since 2022)

With

server = createSocksServer({
    connectionFilter: (destination: SocksConnectionInfo, origin: SocksConnectionInfo, callback: (err?: unknown, dest?: stream.Duplex) => void) => {
        this.connect().then(() => {
            this.sshConnection!.forwardOut(
                origin.address,
                origin.port,
                destination.address,
                destination.port,
                (err, stream) => {
                    if (err) {
                        this.emit(SSHConstants.CHANNEL.TUNNEL, SSHConstants.STATUS.DISCONNECT, { SSHTunnelConfig: SSHTunnelConfig, err: err });
                        return callback(err);
                    }
                    return callback(null, stream);
                });
        });
    }
}).on('proxyError', (err: unknown) => {
    this.emit(SSHConstants.CHANNEL.TUNNEL, SSHConstants.STATUS.DISCONNECT, { SSHTunnelConfig: SSHTunnelConfig, err: err });
});

at https://github.com/jeanp413/open-remote-ssh/blob/master/src/ssh/sshConnection.ts#L272

I've just become a maintainer of that project and want to contribute it back to your project.

[codecov]

Codecov Report

❌ Patch coverage is 80.53691% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.03%. Comparing base (641b108) to head (a6717aa).

Files with missing lines	Patch %	Lines
src/socks5.js	80.53%	29 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #76      +/-   ##
==========================================
- Coverage   86.75%   84.03%   -2.73%     
==========================================
  Files           2        2              
  Lines         657      689      +32     
==========================================
+ Hits          570      579       +9     
- Misses         87      110      +23     

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[brozeph]

hi @daiyam - can you take a look at #77? I'm trying a slightly different approach to accomplish the same goal... I had some reservations about overloading the connectionFilter option and thought this is a strong use case to warrant a more direct approach.

[brozeph]

Closing in lui of PR #77

[daiyam]

Sorry, I didn't had the time to validate your PR (I did read it but had no time to use it and to check if it was ok). As soon as, I uses it, I will get back to you. Thanks for your PR.