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net_utils.py
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net_utils.py
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#!/usr/bin/env python3
assert __name__ != '__main__'
import logging
import os
import pathlib
import platform
import socket
import struct
import subprocess
import sys
import threading
import time
import traceback
# --
# Subclass OSError, because it's not usually useful to rely on detecting a
# 'clean' shutdown like this.
class ex_recv_n_eof(OSError):
pass
# --
def recv_n(conn, n):
ret = bytearray(n)
if n:
view = memoryview(ret)
while view:
got = conn.recv_into(view)
if not got:
raise ex_recv_n_eof()
view = view[got:]
return bytes(ret)
# --
U8_T = struct.Struct('<B')
U16_T = struct.Struct('<H')
I32_T = struct.Struct('<i')
U32_T = struct.Struct('<I')
U64_T = struct.Struct('<Q')
BOOL_T = struct.Struct('<?')
F64_T = struct.Struct('<d')
# --
def pack_t(type_struct, v):
b = type_struct.pack(v)
return b
def unpack_t(type_struct, b):
(v,) = type_struct.unpack(b)
return v
# --
def send_t(conn, type_struct, v):
conn.sendall(type_struct.pack(v))
def recv_t(conn, type_struct):
b = recv_n(conn, type_struct.size)
(v,) = type_struct.unpack(b)
return v
# --
def send_bytes(conn, b):
if len(b) < 0xff:
send_t(conn, U8_T, len(b))
else:
send_t(conn, U8_T, 0xff)
send_t(conn, U64_T, len(b))
conn.sendall(b)
def recv_bytes(conn):
b_len = recv_t(conn, U8_T)
if b_len == 0xff:
b_len = recv_t(conn, U64_T)
return recv_n(conn, b_len)
# --
#def set_keepalive(conn, approx=None, after_idle_sec=1, interval_sec=1, max_fails=10):
# if approx:
# after_idle_sec = approx / 2
# interval_sec = approx / 2
# interval_sec /= max_fails
#
# conn.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
#
# if platform.system() == 'Darwin':
# # scraped from /usr/include, not exported by python's socket module
# TCP_KEEPALIVE = 0x10
# total_sec = after_idle_sec + interval_sec * max_fails
# sock.setsockopt(socket.IPPROTO_TCP, TCP_KEEPALIVE, total_sec)
# return
#
# if platform.system() == 'Linux':
# conn.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, max_fails)
# elif platform.system() == 'Windows':
# # On Windows Vista and later, the number of keep-alive probes (data
# # retransmissions) is set to 10 and cannot be changed.
# # On Windows Server 2003, Windows XP, and Windows 2000, the default
# # setting for number of keep-alive probes is 5.
# interval_sec *= max_fails
# max_fails = 10
# interval_sec /= max_fails
# '''
# # Not needed anymore?
# >
# tcp_keepalive = (onoff, after_idle_sec*1000, interval_sec*1000)
# sock.ioctl(socket.SIO_KEEPALIVE_VALS, tcp_keepalive)
# '''
# else:
# assert False, platform.system()
#
# conn.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, after_idle_sec)
# conn.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, interval_sec)
# --
def nuke_socket(conn):
try:
conn.shutdown(socket.SHUT_RDWR)
except OSError:
pass
try:
conn.close()
except OSError:
pass
# --
class Server(object):
def __init__(self, addrs, target, on_accept_args=()):
self.addrs = set(addrs)
self.fn_on_accept = target
self.on_accept_args = tuple(on_accept_args)
self.lock = threading.Lock()
self.alive = True
self.s_by_gai = {}
return
def listen_until_shutdown(self, daemon=True):
threading.Thread(target=self.listen_loop, daemon=daemon).start()
def listen_loop(self):
while True:
gais = set()
for (host,port) in self.addrs:
gais |= set(socket.getaddrinfo(host, port, proto=socket.IPPROTO_TCP))
with self.lock:
if not self.alive:
break
new_gais = gais.difference(self.s_by_gai.keys())
for gai in new_gais:
s = socket.socket(gai[0])
try:
s.bind(gai[4])
except OSError:
logging.warning('Failed to socket.bind({}).'.format(gai[4]))
continue
try:
s.listen()
except OSError:
traceback.print_exc()
continue
self.s_by_gai[gai] = s
threading.Thread(target=self._th_accept_loop, args=(gai, s)).start()
time.sleep(1.0)
continue
return
def shutdown(self):
with self.lock:
self.alive = False
for x in self.s_by_gai.values():
nuke_socket(x)
def get_gais(self):
with self.lock:
return set(self.s_by_gai.keys())
def _th_accept_loop(self, gai, s):
while True:
try:
(conn, addr) = s.accept()
except OSError:
break
threading.Thread(target=self._th_on_accept, args=(conn, addr)).start()
continue
nuke_socket(s)
with self.lock:
del self.s_by_gai[gai]
return
def _th_on_accept(self, conn, addr):
try:
self.fn_on_accept(conn=conn, addr=addr, *(self.on_accept_args))
except Exception as e:
traceback.print_exc()
nuke_socket(conn)
return
# --
def connect_any(addrs, timeout=socket.getdefaulttimeout()):
gais = set()
for (host,port) in addrs:
gai = socket.getaddrinfo(host, port, proto=socket.IPPROTO_TCP)
gais |= set(gai)
s_addr_list = [(socket.socket(gai[0]), gai[4]) for gai in gais]
completion_sem = threading.Semaphore(0)
winner_lock = threading.Lock()
winner = [None] # box
def fn_thread(s, remote_addr):
try:
try:
s.settimeout(timeout)
s.connect(remote_addr)
except socket.timeout:
return
except OSError:
if not winner[0]:
return
if winner_lock.acquire(blocking=False):
winner[0] = s
for (s2,_) in s_addr_list:
if s2 != s:
nuke_socket(s2)
for _ in s_addr_list:
completion_sem.release()
return
finally:
completion_sem.release()
return
for s_addr in s_addr_list:
threading.Thread(target=fn_thread, args=tuple(s_addr), daemon=True).start()
for _ in s_addr_list:
completion_sem.acquire()
return winner[0]
# --
class ex_pc_bad_magic(OSError):
pass
class PacketConn(object):
MAGIC = b'\x91\x7c\x56\x3e' # via hex(random.getrandbits(32))
def __init__(self, conn, timeout=False, keepalive=False, **kwargs):
self.alive = True
self.conn = conn
self.slock = threading.RLock()
self.rlock = threading.RLock()
self.keepalive_cond = threading.Condition()
self.keepalive_ratio = 2.5
self.keepalive_thread = None
try:
self.magic = kwargs['magic']
except KeyError:
self.magic = self.MAGIC
self.awaiting_magic = True
if timeout != False:
self.set_timeout(timeout, keepalive=keepalive)
try:
self.send(self.magic)
except OSError:
self.nuke()
# If we raise here, we never assign, complicating error handling.
pass
LONG_LEN_THRESHOLD = 0xfe
KEEP_ALIVE_VAL = 0xff
def send(self, b):
with self.slock:
if len(b) < self.LONG_LEN_THRESHOLD:
send_t(self.conn, U8_T, len(b))
else:
send_t(self.conn, U8_T, self.LONG_LEN_THRESHOLD)
send_t(self.conn, U64_T, len(b))
if len(b):
self.conn.sendall(b)
def recv(self):
try:
with self.rlock:
if self.awaiting_magic:
self.awaiting_magic = False
remote_magic = self.recv()
if remote_magic != self.magic:
err = 'Expected MAGIC {}, was {}'.format(self.magic, remote_magic)
logging.warning(err)
ex = ex_pc_bad_magic(err)
ex.remote_magic = remote_magic
raise ex
while True:
b_len = recv_t(self.conn, U8_T)
if b_len == self.KEEP_ALIVE_VAL:
continue
if b_len == self.LONG_LEN_THRESHOLD:
b_len = recv_t(self.conn, U64_T)
b = b''
if b_len:
b = recv_n(self.conn, b_len)
return b
except OSError:
self.nuke()
raise
def send_t(self, t, v):
b = pack_t(t, v)
self.send(b)
def recv_t(self, t):
b = self.recv()
return unpack_t(t, b)
def set_keepalive(self, on):
with self.keepalive_cond:
if on == bool(self.keepalive_thread):
return
if on:
self.keepalive_thread = threading.Thread(target=self._th_keepalive, daemon=True)
self.keepalive_thread.start()
else:
self.keepalive_thread = None
self.keepalive_cond.notify()
def set_timeout(self, secs, keepalive=None):
with self.keepalive_cond:
self.conn.settimeout(secs)
self.keepalive_cond.notify()
if keepalive != None:
self.set_keepalive(keepalive)
# Useful info:
# * https://stackoverflow.com/questions/3757289/tcp-option-so-linger-zero-when-its-required)
# * https://docs.microsoft.com/en-us/windows/desktop/WinSock/graceful-shutdown-linger-options-and-socket-closure-2
# Sender should send_shutdown instead of nuking, when done.
def send_shutdown(self):
self.set_keepalive(False)
try:
self.conn.shutdown(socket.SHUT_WR)
except socket.error:
pass
self.wait_for_disconnect()
# Allows sending on other threads still.
def wait_for_disconnect(self):
try:
self.recv()
assert False
except OSError:
pass
self.nuke()
def nuke(self):
self.alive = False
self.set_keepalive(False)
nuke_socket(self.conn)
def _th_keepalive(self):
with self.keepalive_cond:
try:
while True:
timeout = self.conn.gettimeout()
if timeout:
timeout /= self.keepalive_ratio
else:
# Wait forever if forever-blocking *or* non-blocking.
timeout = None
self.keepalive_cond.wait(timeout)
if not self.keepalive_thread:
return
with self.slock:
send_t(self.conn, U8_T, self.KEEP_ALIVE_VAL)
except OSError: # Remote socket shutdown?
pass
finally:
self.keepalive_thread = None
self.nuke()