add rtorrent scgi proxy for dumb use case

rtorrent_proxy.py

@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+"""
+This file handles a rather silly use case:
+You have two servers, A and B, each with various rtorrent instances running.
+You want one instance of Aberrant, running on server A. In your infinite
+wisdom, you bound the SCGI ports of the rtorrent instances on server B to
+localhost, leaving Aberrant unable to query them. Rtorrent won't allow you
+to rebind the SCGI port while it's running, and you don't want to restart
+the rtorrent instance(s) because restarting stuff sucks. Therefore, you
+need another way for Aberrant to communicate to them.
+
+This script acts as a proxy to the rtorrent instances on server B. It will
+listen on a port (don't forget to open the port in your iptables), and
+relay all data it receives to the torrent SCGI port and vice versa.
+
+To use:
+Configure `port_mapping` in the form `listen_port`: `rtorrent_port`.
+Run the script on server B.
+"""
+import socket
+import threading
+
+port_mapping = {
+	4000: 5000,
+	4001: 5001,
+	4002: 5002,
+}
+
+class SocketProxy(threading.Thread):
+	"""Represents a proxy to an rTorrent SCGI port."""
+	def __init__(self, listen_port, rtorrent_port):
+		super().__init__()
+		self.listen_port = listen_port
+		self.rtorrent_port = rtorrent_port
+		self._stop_event = threading.Event()
+
+	def stop(self):
+		"""Sets the internal 'stop running' flag."""
+		self._stop_event.set()
+
+	def stopped(self):
+		"""Returns true if the internal stop flag has been set."""
+		return self._stop_event.is_set()
+
+	def run(self):
+		with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+			s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+			s.settimeout(1)
+			s.bind(('0.0.0.0', self.listen_port))
+			s.listen(1)
+			while not self.stopped():
+				try:
+					conn, addr = s.accept() # client connected
+				except socket.timeout:
+					continue
+				with conn:
+					# receive data from client
+					data = []
+					data.append(conn.recv(1024)) # the header really shouldn't be longer than this...
+					header = data[0].partition(b',')[0]
+					body_len = int(header.split(b'\x00')[1])
+					recv_len = len(data[0])
+					while recv_len < body_len + len(header) + 1:
+						data.append(conn.recv(1024))
+						recv_len += len(data[-1])
+					data = b''.join(data)
+
+					with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as rt_conn:
+						rt_conn.connect(('127.0.0.1', self.rtorrent_port))
+						rt_conn.sendall(data) # send to rtorrent
+
+						# receive data from rtorrent
+						data = []
+						data.append(rt_conn.recv(1024))
+						header = data[0].partition(b'<?xml')[0]
+						body_len = header.split(b'\r\n')[2].partition(b' ')[2]
+						body_len = int(body_len)
+						recv_len = len(data[0])
+						while recv_len < body_len + len(header):
+							data.append(rt_conn.recv(1024))
+							recv_len += len(data[-1])
+						data = b''.join(data)
+					conn.sendall(data) # send to client
+
+def run_proxies():
+	"""Run all proxies."""
+	proxies = []
+	for listen_port, rtorrent_port in port_mapping.items():
+		p = SocketProxy(listen_port, rtorrent_port)
+		p.start()
+		proxies.append(p)
+
+	try:
+		proxies[0].join()
+	except KeyboardInterrupt:
+		for p in proxies:
+			p.stop()
+
+if __name__ == '__main__':
+	run_proxies()