Remote Daemon Control Protocol
rdcp is a protocol for controlling a daemon remotely. It is designed to be simple and easy to implement. It is also designed to be secure, and to be able to be used over an insecure connection. It's still in development, not meant for use yet.
Initial motivation of implementation is to use it with a remote docker daemon control tool (drun). However, it is not limited to docker, and can be used with any daemon, if tailored to that daemon.
RDCP presents 4 different methods of request.
- ORDER
- PROXY
- OPTIONS
- HEARTBEAT
ORDER method is used to send a command to the daemon. It is a simple string, and some optional parameters. Daemon is expected to execute a command/function based on the string, and return a response. It is similar to RPC but the message is not in binary format.
ORD
Version: 0.1
Time: 1686604453
OrderedAction(parameter1=value1,parameter2=value2)
R/ORD
Version: 0.1
From: 192.168.0.1
Received: 1686604453
Replied: 1686604700
Hello, World!
PROXY method is used to proxy a connection to the daemon. It is used to connect to a daemon, and send/receive data to/from it. It is similar to SSH tunneling.
Daemon is expected to proxy the request to the target, and return the response.
PRX
Version: 0.1
Time: 1686604453
Host: example.com
GET / HTTP/1.1
Host: example.com
R/PRX
Version: 0.1
From: 192.168.0.1
Proxied-To: example.com
Received: 1686604453
Replied: 1686604700
Hello, World!
OPTIONS method is used to get the options of the daemon. It is used to get the options of the daemon, and return the response. It is similar to HTTP OPTIONS. It can be used to decide on the capabilities of the daemon.
OPT
Version: 0.1
Time: 1686604453
localhost?
R/OPT
Version: 0.1
From: 192.168.0.1
Received: 1686604453
Replied: 1686604700
192.168.0.7
HEARTBEAT method is used to ping the server. It is similar to HTTP HEAD. It can be used to keep the connection alive.
HBT
Version: 0.1
Time: 1686604453
R/HBT
Version: 0.1
From: 192.168.0.1
Received: 1686604453
Replied: 1686604700
RDCP is designed to be used over an insecure connection. However, it is also designed to be able to be used over a secure connection. It is recommended to use a secure connection, if possible. A RDCP over TLS is available. It is recommended to use so.
There's no authentication mechanism available in RDCP since it is a stateless protocol like HTTP. It is possible and recommended to use Authorization header for authentication like used in HTTP. It is also possible to use a custom header for authentication.
Version header indicates the version the client/server is using to communicate. Communicating parties can tolerate version differences as long as the major version is the same. If the major version is different, communicating parties should not communicate.
- Sent by:
Client/Server - Type:
const string enum, Values: (0.1)
Time header indicates the time the request is sent. It is used to calculate the latency of the request. It is also used to calculate the time the request is received and replied.
- Sent by:
Client - Type:
int64
From header indicates the IP address of the client. It is used to identify the client.
- Sent by:
Server - Type:
string
Received header indicates the local time of the server when request is received. It is used to calculate the latency of the request.
- Sent by:
Server - Type:
int64
Replied header indicates the local time of the server when request is replied. It is used to calculate the latency of the request.
- Sent by:
Server - Type:
int64
Host header indicates the host the request is sent to. It is used to proxy the request to the target.
- Sent by:
Client - Type:
string
Proxied-To header indicates the host the request is proxied to. It is used to proxy the request to the target.
- Sent by:
Server - Type:
string