ProcsLink - IPC over Netlink Socket

Introduction

This module is used for interprocess communication (IPC) for processes in difference namespaces. I designed and wrote this module because existing IPC libraries are not suitable for inter-namespaces communication.

Currently, I have implemented a JSON-RPC interface.

Install from PyPI

sudo pip install procslink

API Usage Demo

Run JSON-RPC server

importosfromprocslinkimportRPCPeerclassMyAPI(object):
defhello(self, name):
s="Hello, %s!"%nameprint(s)
returnsrpc_server=RPCPeer()
print("Server's nl_pid is %s."%rpc_server.nl_pid)
rpc_server.register_functions_in_object(MyAPI())
rpc_server.run_server_forever()

Run JSON-RPC client

fromprocslinkimportRPCPeer# server_nl_pid is server's nl_pidrpc_client=RPCPeer()
rpc_client.talk_to(server_nl_pid).hello("Rayson Zhu")

Parse bytes to message objects

# suppose data is a raw Netlink message bytesnetlink_message=NetlinkMessage.from_bytes(data)
procslink_message=ProcslinkMessage.from_bytes(netlink_message.payload)
jsonrpc_request=JSONRPCRequest.from_bytes(procslink_message.payload)

Convert message objects to raw bytes

jsonrpc_response=JSONRPCResponse(id=123, result=True)
procslink_header=ProcslinkMessageHeader(
payload_type=ProcslinkMessageHeader.PAYLOAD_TYPE_JSONRPC2_RESPONSE)
procslink_message=ProcslinkMessage(procslink_header,
jsonrpc_response.to_bytes()))
netlink_header=NetlinkMessageHeader(nlmsg_pid=sender_nl_pid)
netlink_message=NetlinkMessage(netlink_header,
procslink_message.to_bytes())
data=netlink_message.to_bytes()

Design

Messages are delivered over Netlink(7). Before reading this document, you should read the above link first.

ProcsLink uses the following message format:

+-----------------------+
| nlmsghdr |
+-----------------------+
| procslinkhdr |
+-----------------------+
| JSON-RPC message |
+-----------------------+

Where

• nlmsghdr is the raw Netlink header.
• procslinkhdr is our own defined header for extension (because we may run different protocolsother than JSON-RPC in the future),
• JSON-RPC message is the JSON-RPC request/response body encoded in UTF-8. JSON-RPC 2.0 is used.

Following is the defination of struct procslinkhdr:

/* connectorhdr (8 bytes) */structprocslinkhdr {
uint16_tversion; /* version number, default: 1 */uint16_tflag; /* reserved */uint32_tlength; /* message length including this header */uint16_tpayload_type; /* payload_type message type ID */uint16_treserved; /* reserved */uint32_tseq; /* sequence number */uint64_ttimestamp; /* when this message is sent */
};

Dependencies

• python-future: to be compatible with both Python 2 and 3

Directory Structure

+ procslink
- __init__.py
- common.py
- jsonrpc.py
- netlink.py
- procslink.py

Where

• __init__.py defines the JSON-RPC server/client: RPCPeer.
• common.py defines the base class for message headers and messages.
• netlink.py defines NetlinkMessageHeader and NetlinkMessage, which are abstraction for Netlink header and whole netlink meesages.
• procslink.py defines message data structures for the Procslink message layer.
• jsonrpc.py defines models for JSON-RPC 2.0 request object, response object, and error object, etc.