Pluggable Transport Client Per-Connection Arguments

Certain PT transport protocols require that the client provides per-connection arguments when making outgoing connections. On the server side, this is handled by the "ARGS" optional argument as part of the "SMETHOD" message.

On the client side, arguments are passed via the authentication fields that are part of the SOCKS protocol.

First the "<Key>=<Value>" formatted arguments MUST be escaped, such that all backslash, equal sign, and semicolon characters are escaped with a backslash.

Second, all of the escaped are concatenated together.



Lastly the arguments are transmitted when making the outgoing connection using the authentication mechanism specific to the SOCKS protocol version.

    - In the case of SOCKS 4, the concatenated argument list is
      transmitted in the "USERID" field of the "CONNECT" request.

    - In the case of SOCKS 5, the parent process must negotiate
      "Username/Password" authentication [RFC1929], and transmit
      the arguments encoded in the "UNAME" and "PASSWD" fields.

If the encoded argument list is less than 255 bytes in length, the "PLEN" field must be set to "1" and the "PASSWD" field must contain a single NUL character.