TCP Transport¶

Wire Protocol¶

This implementation over TCP focuses on flexibility over absolute efficiency. This means we are okay to spend a couple of bytes of wire space for flexibility in the future. That being said, the wire framing is quite efficient and looks like:

msgpack({'head': SOMEHEADER, 'body': SOMEBODY})

Since msgpack is an iterably parsed serialization, we can simply write the serialized payload to the wire. Within that payload we have two items "head" and "body". Head contains header information (such as "message id"). The Body contains the actual message that we are sending. With this flexible wire protocol we can implement any message semantics that we'd like-- including multiplexed message passing on a single socket.

TLS Support¶

The TCP transport allows for the master/minion communication to be optionally wrapped in a TLS connection. Enabling this is simple, the master and minion need to be using the tcp connection, then the ssl option is enabled. The ssl option is passed as a dict and corresponds to the options passed to the Python ssl.wrap_socket <https://docs.python.org/2/library/ssl.html#ssl.wrap_socket> function.

A simple setup looks like this, on the Salt Master add the ssl option to the master configuration file:

ssl:
  keyfile: <path_to_keyfile>
  certfile: <path_to_certfile>
  ssl_version: PROTOCOL_TLSv1_2

The minimal ssl option in the minion configuration file looks like this:

ssl: True
# Versions below 2016.11.4:
ssl: {}

Specific options can be sent to the minion also, as defined in the Python ssl.wrap_socket function.

Crypto¶

The current implementation uses the same crypto as the zeromq transport.

Pub Channel¶

For the pub channel we send messages without "message ids" which the remote end interprets as a one-way send.

Req Channel¶

For the req channel we send messages with a "message id". This "message id" allows us to multiplex messages across the socket.