/
port-forwarder.py
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/
port-forwarder.py
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#!/usr/bin/env python3
import argparse
import logging
import os
import time
import platform
from collections import namedtuple, deque
from select import select
from socket import socket, AF_INET, SOCK_STREAM, SOCK_DGRAM, getdefaulttimeout
from threading import Thread, Lock
from typing import List, Tuple, Set, Optional, Union, Dict
CHUNK_SIZE_B = 4096 # B
MAX_MEMORY_B = 16 * (1024 ** 2) # 16MiB
SOCKET_IDLE_TIMEOUT = 120 # s, 0 to disabled
SOCKET_IDLE_TCP_TIMEOUT_ENABLED = False
PROXY_INFO = namedtuple('ProxyInfo', ['host', 'port', 'tcp'])
PROXY_PAIR = Tuple[PROXY_INFO, PROXY_INFO] # from, to
ProxyOrPipe = Union["ProxySocket", int]
class ProxySocket(socket):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.is_server: bool = False
self.info: Optional[PROXY_INFO] = None
self.proxy_to: Optional[Union[PROXY_INFO, "ProxySocket"]] = None
self.read_cache_lock = Lock()
self.read_cache: deque[bytes] = deque()
self.write_cache: deque[bytes] = deque()
self.last_used = time.time()
def accept(self) -> "ProxySocket":
# noinspection PyUnresolvedReferences
fd, addr = self._accept()
sock = ProxySocket(self.family, self.type, self.proto, fileno=fd)
if getdefaulttimeout() is None and self.gettimeout():
sock.setblocking(True)
return sock
def memory_usage(self) -> int:
return sum(map(lambda x: len(x), self.read_cache)) + sum(map(lambda x: len(x), self.write_cache))
def create_socket_server(info: PROXY_INFO, wait_for_port=False) -> ProxySocket:
s = ProxySocket(AF_INET, SOCK_STREAM if info.tcp else SOCK_DGRAM)
s.is_server = True
s.info = info
s.setblocking(False)
while True:
try:
s.bind((info.host, info.port))
break
except OSError:
if wait_for_port:
logging.info(f'[SERV] {info}\'s port is not ready to be taken, retrying in 5 seconds')
time.sleep(5)
else:
raise
if info.tcp:
s.listen(10)
return s
def create_proxy_servers(pairs: List[PROXY_PAIR], wait_for_ports=False) -> List[ProxySocket]:
servers: List[ProxySocket] = []
for proxy_from, proxy_to in pairs:
server = create_socket_server(proxy_from, wait_for_ports)
server.proxy_to = proxy_to
servers.append(server)
return servers
def create_client_connection(source: Union[ProxySocket, PROXY_INFO], target: PROXY_INFO) -> ProxySocket:
s = ProxySocket(AF_INET, SOCK_STREAM if target.tcp else SOCK_DGRAM)
if target.tcp:
s.connect((target.host, target.port))
s.proxy_to = source
return s
def run_proxy(pairs: List[PROXY_PAIR],
uid: Optional[int] = None,
guid: Optional[int] = None,
wait_for_port=False) -> None:
servers = create_proxy_servers(pairs, wait_for_port)
if guid is not None or uid is not None:
from os import setuid, setgid
setgid(guid)
setuid(uid)
try:
__run_proxy_loop(servers)
finally:
print('stopping servers')
[s.close() for s in servers]
def __run_proxy_loop(servers: List[ProxySocket]) -> None:
os_windows = platform.system() == 'Windows'
# this server will be notified when a new connection is established in order to unblock select
if os_windows:
pipe_unblock_select_read = create_socket_server(PROXY_INFO(host='127.0.0.1', port=0, tcp=False))
pipe_unblock_select_write = socket(AF_INET, SOCK_DGRAM)
else:
pipe_unblock_select_read, pipe_unblock_select_write = os.pipe()
all_readers: List[ProxyOrPipe] = []
all_writers: List[ProxySocket] = []
data_memory_usage = 0
udp_sockets: Dict[Tuple[str, int], ProxySocket] = {}
last_time_inactive_removed = time.time()
def can_open_more_sockets() -> bool:
return max(len(all_readers) + len(servers), len(all_writers)) < (500 if os_windows else 1000)
def unblock_select_wait() -> None:
if os_windows:
pipe_unblock_select_write.sendto(b'1', pipe_unblock_select_read.getsockname())
else:
os.write(pipe_unblock_select_write, b'1')
while True:
dead_sockets: Set[ProxySocket] = set()
if SOCKET_IDLE_TIMEOUT and time.time() - last_time_inactive_removed > min(180, SOCKET_IDLE_TIMEOUT):
last_time_inactive_removed = time.time()
logging.debug('[MEM] removing inactive sockets')
sockets = all_readers if SOCKET_IDLE_TCP_TIMEOUT_ENABLED else udp_sockets.values()
for s in sockets:
if type(s) is int or s.is_server or time.time() - s.last_used < SOCKET_IDLE_TIMEOUT:
continue
dead_sockets.add(s)
if isinstance(s.proxy_to, ProxySocket):
dead_sockets.add(s)
memory_usage = data_memory_usage + len(all_readers) * 1360
if memory_usage < MAX_MEMORY_B:
possible_readers = all_readers + [pipe_unblock_select_read]
if can_open_more_sockets():
possible_readers.extend(servers)
else:
logging.warning("[MEM] To much opened sockets, cannot accept more")
else:
possible_readers = []
logging.debug(f'[MEM] {memory_usage // 1024} / {MAX_MEMORY_B // 1024} kiB used')
possible_writes = list(filter(lambda x: x.write_cache, all_writers))
logging.debug(f'[LOOP] possible readers {len(possible_readers)}, writers {len(possible_writes)}')
try:
readers, writers, err = select(possible_readers, possible_writes,
list(set(possible_writes + possible_readers))
) # type: List[ProxySocket], List[ProxySocket], List[ProxySocket]
logging.debug(f'[LOOP] selected readers {len(readers)}, writers {len(writers)}, in error {len(err)}')
dead_sockets.update(err)
except ValueError:
readers = writers = []
logging.debug('[LOOP] invalid socket found, removing')
for s in filter(lambda x: isinstance(x, ProxySocket) and x.fileno() < 0, all_readers): # type: ProxySocket
dead_sockets.add(s)
if isinstance(s.proxy_to, ProxySocket):
dead_sockets.add(s.proxy_to)
for reader in readers:
if reader in dead_sockets:
continue
if reader == pipe_unblock_select_read:
logging.debug(f'[ACC] unblocking request received')
if os_windows:
pipe_unblock_select_read.recvfrom(1)
else:
os.read(pipe_unblock_select_read, 1)
elif reader.is_server:
if not can_open_more_sockets():
logging.warning("[ACC] to much opened sockets, rejecting")
continue
if reader.info.tcp:
logging.debug(f'[ACC] accepting new client to {reader.info}')
try:
new_client = reader.accept()
except (BlockingIOError, ConnectionError, OSError):
continue
all_writers.append(new_client)
all_readers.append(new_client)
proxy_info = reader.proxy_to
logging.debug(f'[ACC] new client accepted: {new_client.fileno()} {new_client.getpeername()}')
def f():
try:
logging.debug(f'[C] {new_client.fileno()}: creating peer connection')
proxy_to = create_client_connection(new_client, proxy_info)
logging.debug(f'[C] {new_client.fileno()}: peer connection created as {proxy_to.fileno()}')
with new_client.read_cache_lock:
proxy_to.write_cache.extend(new_client.read_cache)
new_client.proxy_to = proxy_to
new_client.read_cache.clear()
logging.debug(f'[C] {new_client.fileno()}: first cache copied to {proxy_to.fileno()}')
all_readers.append(proxy_to)
all_writers.append(proxy_to)
unblock_select_wait()
except ConnectionError:
new_client.close()
Thread(target=f, daemon=True).start()
else:
try:
data, address = reader.recvfrom(CHUNK_SIZE_B)
except (BlockingIOError, OSError, ConnectionError):
continue
target = reader.proxy_to
if address not in udp_sockets:
soc = create_client_connection(
PROXY_INFO(host=address[0], port=address[1], tcp=False),
target
)
udp_sockets[address] = soc
all_readers.append(soc)
else:
soc = udp_sockets[address]
try:
soc.sendto(data, (target.host, target.port))
except (BlockingIOError, OSError, ConnectionError):
logging.debug(f'[KILL] UDP send failed {reader.fileno()}')
dead_sockets.add(soc)
else:
reader.last_used = time.time()
try:
data = reader.recv(CHUNK_SIZE_B)
data_memory_usage += len(data)
except (BlockingIOError, OSError, ConnectionError):
data = bytes(0)
if not data:
logging.debug(f'[KILL] no data read or error from {reader.fileno()}')
dead_sockets.add(reader)
data_memory_usage -= reader.memory_usage()
if isinstance(reader.proxy_to, ProxySocket):
dead_sockets.add(reader.proxy_to)
data_memory_usage -= reader.proxy_to.memory_usage()
else:
if reader.proxy_to is not None:
if isinstance(reader.proxy_to, ProxySocket):
reader.proxy_to.write_cache.append(data)
else:
reader.sendto(data, (reader.proxy_to.host, reader.proxy_to.port))
data_memory_usage -= len(data)
else:
with reader.read_cache_lock:
if reader.proxy_to is not None:
reader.proxy_to.write_cache.append(data)
else:
reader.read_cache.append(data)
for writer in writers:
if writer in dead_sockets:
continue
writer.last_used = time.time()
if len(writer.write_cache):
write_bytes = writer.write_cache.popleft()
try:
sent_count = writer.send(write_bytes)
if sent_count < len(write_bytes):
write_bytes = write_bytes[sent_count:]
writer.write_cache.appendleft(write_bytes)
data_memory_usage -= sent_count
except (BlockingIOError, OSError, ConnectionError):
logging.debug(f'[KILL] write error for {writer.fileno()}')
dead_sockets.add(writer)
data_memory_usage -= writer.memory_usage()
if isinstance(writer.proxy_to, ProxySocket):
dead_sockets.add(writer.proxy_to)
data_memory_usage -= writer.proxy_to.memory_usage()
for dead in dead_sockets:
logging.debug(f"[KILL] killing {dead.fileno()}")
dead.read_cache.clear()
dead.write_cache.clear()
try:
dead.close()
except (OSError, ConnectionError):
pass
try:
all_writers.remove(dead)
except ValueError:
pass
try:
all_readers.remove(dead)
except ValueError:
pass
def main() -> int:
parser = argparse.ArgumentParser(description='Runs a proxy from point A to point B')
parser.add_argument('local_ip', metavar='localIP', type=str, help='an IP address to bind')
parser.add_argument('local_port', metavar='localPort', type=int, help='a port to bind')
parser.add_argument('remote_ip', metavar='remoteIP', type=str, help='an IP address to proxy to')
parser.add_argument('remote_port', metavar='remotePort', type=int, help='a port to proxy to')
parser.add_argument('--user', metavar='user', type=str, help='change uid to user', default='')
parser.add_argument('--group', metavar='group', type=str, help='change guid to user', default='')
parser.add_argument('--udp', dest='udp', action='store_const', const=True, default=False,
help='use UDP instead of TCP')
parser.add_argument('--debug', dest='debug', action='store_const', const=True, default=False,
help='be more verbose')
parser.add_argument('--wait-for-port', dest='portWait', action='store_const', const=True, default=False,
help='if the port is taken now, wait until it becomes available')
args = parser.parse_args()
uid: Optional[int] = None
guid: Optional[int] = None
if args.user or args.group:
try:
# noinspection PyUnresolvedReferences
import grp
# noinspection PyUnresolvedReferences
import pwd
if args.user:
uid = pwd.getpwnam(args.user).pw_uid
if args.group:
guid = grp.getgrnam(args.group).gr_gid
except ModuleNotFoundError:
print("Cannot determine user's UID / GUID")
return 1
logging.basicConfig(level=logging.DEBUG if args.debug else logging.INFO)
run_proxy([(
PROXY_INFO(host=args.local_ip, port=args.local_port, tcp=not args.udp),
PROXY_INFO(host=args.remote_ip, port=args.remote_port, tcp=not args.udp)
)], uid=uid, guid=guid, wait_for_port=args.portWait)
return 0
if __name__ == '__main__':
try:
exit(main())
except KeyboardInterrupt:
print("exiting")
exit(2)