302 lines
9.3 KiB
Python
302 lines
9.3 KiB
Python
|
#!/usr/bin/env python3
|
||
|
|
"""
|
||
|
|
RemSound UDP relay.
|
||
|
|
|
||
|
|
Listens on a single UDP port and reflects RemSound packets between up to two
|
||
|
|
peer endpoints. Validates the 12-byte RemSound header (magic 'RMND', version 1)
|
||
|
|
and silently drops anything else. Never decodes audio.
|
||
|
|
|
||
|
|
Pairing model: pragmatic v1. The relay does not key on stream id (two RemSound
|
||
|
|
instances will use different per-sender stream ids, so keying on it would
|
||
|
|
prevent pairing). Instead the first two distinct UDP endpoints to send a valid
|
||
|
|
RemSound packet claim the two peer slots; subsequent valid packets from a
|
||
|
|
slot's endpoint are reflected to the other slot. Slots that go silent for more
|
||
|
|
than IDLE_TIMEOUT_SECONDS are replaced when a fresh endpoint arrives.
|
||
|
|
|
||
|
|
Spec and operational notes: see README.md alongside this script.
|
||
|
|
"""
|
||
|
|
|
||
|
|
from __future__ import annotations
|
||
|
|
|
||
|
|
import argparse
|
||
|
|
import logging
|
||
|
|
import logging.handlers
|
||
|
|
import select
|
||
|
|
import signal
|
||
|
|
import socket
|
||
|
|
import struct
|
||
|
|
import sys
|
||
|
|
import time
|
||
|
|
from dataclasses import dataclass
|
||
|
|
from typing import Optional
|
||
|
|
|
||
|
|
LISTEN_HOST = "0.0.0.0"
|
||
|
|
DEFAULT_PORT = 47830
|
||
|
|
RECV_BUFFER_BYTES = 2048
|
||
|
|
IDLE_TIMEOUT_SECONDS = 60
|
||
|
|
STATS_INTERVAL_SECONDS = 60
|
||
|
|
SOCKET_POLL_TIMEOUT_SECONDS = 1.0
|
||
|
|
DEFAULT_LOG_PATH = "/var/log/remsound-relay.log"
|
||
|
|
|
||
|
|
# Wire format constants — little-endian, see RemSound.Core.RemPacket.
|
||
|
|
HEADER_LEN = 12
|
||
|
|
MAGIC = b"RMND"
|
||
|
|
VERSION = 1
|
||
|
|
TYPE_FORMAT = 1
|
||
|
|
TYPE_AUDIO = 2
|
||
|
|
TYPE_KEEPALIVE = 3
|
||
|
|
TYPE_HEARTBEAT = 4
|
||
|
|
PACKET_TYPE_NAMES = {
|
||
|
|
TYPE_FORMAT: "Format",
|
||
|
|
TYPE_AUDIO: "Audio",
|
||
|
|
TYPE_KEEPALIVE: "KeepAlive",
|
||
|
|
TYPE_HEARTBEAT: "Heartbeat",
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
@dataclass
|
||
|
|
class PeerSlot:
|
||
|
|
addr: tuple[str, int]
|
||
|
|
last_seen: float
|
||
|
|
rx_packets: int = 0
|
||
|
|
tx_packets: int = 0
|
||
|
|
|
||
|
|
|
||
|
|
@dataclass
|
||
|
|
class RelayStats:
|
||
|
|
forwarded: int = 0
|
||
|
|
dropped_unpaired: int = 0
|
||
|
|
rejected_bad_header: int = 0
|
||
|
|
pair_changes: int = 0
|
||
|
|
|
||
|
|
|
||
|
|
def setup_logger(log_path: str) -> logging.Logger:
|
||
|
|
logger = logging.getLogger("remsound-relay")
|
||
|
|
logger.setLevel(logging.INFO)
|
||
|
|
fmt = logging.Formatter(
|
||
|
|
fmt="%(asctime)s level=%(levelname)s %(message)s",
|
||
|
|
datefmt="%Y-%m-%d %H:%M:%S",
|
||
|
|
)
|
||
|
|
try:
|
||
|
|
fh = logging.handlers.WatchedFileHandler(log_path, encoding="utf-8")
|
||
|
|
fh.setFormatter(fmt)
|
||
|
|
logger.addHandler(fh)
|
||
|
|
except OSError as e:
|
||
|
|
sys.stderr.write(f"remsound-relay: could not open {log_path}: {e}\n")
|
||
|
|
sh = logging.StreamHandler(sys.stderr)
|
||
|
|
sh.setFormatter(fmt)
|
||
|
|
logger.addHandler(sh)
|
||
|
|
return logger
|
||
|
|
|
||
|
|
|
||
|
|
def parse_header(data: bytes) -> Optional[tuple[int, int, int, int]]:
|
||
|
|
"""Validate the RemSound header. Returns (version, type, stream_id, sequence) or None."""
|
||
|
|
if len(data) < HEADER_LEN:
|
||
|
|
return None
|
||
|
|
if data[0:4] != MAGIC:
|
||
|
|
return None
|
||
|
|
version = data[4]
|
||
|
|
if version != VERSION:
|
||
|
|
return None
|
||
|
|
pkt_type = data[5]
|
||
|
|
stream_id = struct.unpack_from("<H", data, 6)[0]
|
||
|
|
sequence = struct.unpack_from("<I", data, 8)[0]
|
||
|
|
return version, pkt_type, stream_id, sequence
|
||
|
|
|
||
|
|
|
||
|
|
class Relay:
|
||
|
|
def __init__(self, sock: socket.socket, log: logging.Logger):
|
||
|
|
self.sock = sock
|
||
|
|
self.log = log
|
||
|
|
self.peers: list[PeerSlot] = []
|
||
|
|
self.stats = RelayStats()
|
||
|
|
self.last_stats_log = time.monotonic()
|
||
|
|
|
||
|
|
@staticmethod
|
||
|
|
def _fmt_addr(addr: tuple[str, int]) -> str:
|
||
|
|
return f"{addr[0]}:{addr[1]}"
|
||
|
|
|
||
|
|
def find_slot(self, addr: tuple[str, int]) -> Optional[int]:
|
||
|
|
for i, p in enumerate(self.peers):
|
||
|
|
if p.addr == addr:
|
||
|
|
return i
|
||
|
|
return None
|
||
|
|
|
||
|
|
def expire_idle(self, now: float) -> None:
|
||
|
|
if not self.peers:
|
||
|
|
return
|
||
|
|
kept: list[PeerSlot] = []
|
||
|
|
dropped: list[tuple[str, int]] = []
|
||
|
|
for p in self.peers:
|
||
|
|
if (now - p.last_seen) <= IDLE_TIMEOUT_SECONDS:
|
||
|
|
kept.append(p)
|
||
|
|
else:
|
||
|
|
dropped.append(p.addr)
|
||
|
|
if dropped:
|
||
|
|
self.peers = kept
|
||
|
|
for addr in dropped:
|
||
|
|
self.log.info(
|
||
|
|
"event=peer_dropped reason=idle addr=%s remaining=%d",
|
||
|
|
self._fmt_addr(addr),
|
||
|
|
len(self.peers),
|
||
|
|
)
|
||
|
|
self.stats.pair_changes += 1
|
||
|
|
|
||
|
|
def admit_or_replace(self, addr: tuple[str, int], now: float) -> int:
|
||
|
|
if len(self.peers) < 2:
|
||
|
|
self.peers.append(PeerSlot(addr=addr, last_seen=now))
|
||
|
|
self.log.info(
|
||
|
|
"event=peer_joined addr=%s slots_filled=%d",
|
||
|
|
self._fmt_addr(addr),
|
||
|
|
len(self.peers),
|
||
|
|
)
|
||
|
|
self.stats.pair_changes += 1
|
||
|
|
if len(self.peers) == 2:
|
||
|
|
self.log.info(
|
||
|
|
"event=peer_paired a=%s b=%s",
|
||
|
|
self._fmt_addr(self.peers[0].addr),
|
||
|
|
self._fmt_addr(self.peers[1].addr),
|
||
|
|
)
|
||
|
|
return len(self.peers) - 1
|
||
|
|
# Both slots occupied. Replace the stalest one if it has been idle.
|
||
|
|
oldest = 0 if self.peers[0].last_seen <= self.peers[1].last_seen else 1
|
||
|
|
if (now - self.peers[oldest].last_seen) > IDLE_TIMEOUT_SECONDS:
|
||
|
|
old_addr = self.peers[oldest].addr
|
||
|
|
self.peers[oldest] = PeerSlot(addr=addr, last_seen=now)
|
||
|
|
self.log.info(
|
||
|
|
"event=peer_replaced old=%s new=%s",
|
||
|
|
self._fmt_addr(old_addr),
|
||
|
|
self._fmt_addr(addr),
|
||
|
|
)
|
||
|
|
self.stats.pair_changes += 1
|
||
|
|
return oldest
|
||
|
|
return -1 # Both slots active — packet from a third endpoint is ignored.
|
||
|
|
|
||
|
|
def handle_packet(self, data: bytes, addr: tuple[str, int]) -> None:
|
||
|
|
parsed = parse_header(data)
|
||
|
|
if parsed is None:
|
||
|
|
self.stats.rejected_bad_header += 1
|
||
|
|
return
|
||
|
|
# We do not log per-packet detail (would flood the log). Stats covers it.
|
||
|
|
_version, _pkt_type, _stream_id, _sequence = parsed
|
||
|
|
|
||
|
|
now = time.monotonic()
|
||
|
|
idx = self.find_slot(addr)
|
||
|
|
if idx is None:
|
||
|
|
# Take the chance to age out idle slots first.
|
||
|
|
self.expire_idle(now)
|
||
|
|
idx = self.admit_or_replace(addr, now)
|
||
|
|
if idx < 0:
|
||
|
|
self.stats.dropped_unpaired += 1
|
||
|
|
return
|
||
|
|
|
||
|
|
peer = self.peers[idx]
|
||
|
|
peer.last_seen = now
|
||
|
|
peer.rx_packets += 1
|
||
|
|
|
||
|
|
if len(self.peers) == 2:
|
||
|
|
other = self.peers[1 - idx]
|
||
|
|
try:
|
||
|
|
self.sock.sendto(data, other.addr)
|
||
|
|
other.tx_packets += 1
|
||
|
|
self.stats.forwarded += 1
|
||
|
|
except OSError as e:
|
||
|
|
self.log.warning(
|
||
|
|
"event=send_failed to=%s err=%s",
|
||
|
|
self._fmt_addr(other.addr),
|
||
|
|
e,
|
||
|
|
)
|
||
|
|
else:
|
||
|
|
self.stats.dropped_unpaired += 1
|
||
|
|
|
||
|
|
def maybe_log_stats(self, now: float) -> None:
|
||
|
|
if (now - self.last_stats_log) < STATS_INTERVAL_SECONDS:
|
||
|
|
return
|
||
|
|
self.last_stats_log = now
|
||
|
|
s = self.stats
|
||
|
|
peers_summary = ", ".join(
|
||
|
|
f"{self._fmt_addr(p.addr)}(rx={p.rx_packets},tx={p.tx_packets})"
|
||
|
|
for p in self.peers
|
||
|
|
) or "none"
|
||
|
|
self.log.info(
|
||
|
|
"event=stats forwarded=%d dropped_unpaired=%d rejected_bad_header=%d pair_changes=%d peers=[%s]",
|
||
|
|
s.forwarded,
|
||
|
|
s.dropped_unpaired,
|
||
|
|
s.rejected_bad_header,
|
||
|
|
s.pair_changes,
|
||
|
|
peers_summary,
|
||
|
|
)
|
||
|
|
# Reset counters so the next stats line shows a per-minute rate.
|
||
|
|
self.stats = RelayStats()
|
||
|
|
for p in self.peers:
|
||
|
|
p.rx_packets = 0
|
||
|
|
p.tx_packets = 0
|
||
|
|
|
||
|
|
|
||
|
|
def main() -> int:
|
||
|
|
parser = argparse.ArgumentParser(description="RemSound UDP relay")
|
||
|
|
parser.add_argument(
|
||
|
|
"--port",
|
||
|
|
type=int,
|
||
|
|
default=DEFAULT_PORT,
|
||
|
|
help=f"UDP port to listen on (default {DEFAULT_PORT})",
|
||
|
|
)
|
||
|
|
parser.add_argument(
|
||
|
|
"--host",
|
||
|
|
default=LISTEN_HOST,
|
||
|
|
help=f"Bind address (default {LISTEN_HOST})",
|
||
|
|
)
|
||
|
|
parser.add_argument(
|
||
|
|
"--log-path",
|
||
|
|
default=DEFAULT_LOG_PATH,
|
||
|
|
help=f"Log file path (default {DEFAULT_LOG_PATH})",
|
||
|
|
)
|
||
|
|
args = parser.parse_args()
|
||
|
|
|
||
|
|
log = setup_logger(args.log_path)
|
||
|
|
log.info("event=startup version=1 listen=%s:%d", args.host, args.port)
|
||
|
|
|
||
|
|
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
|
||
|
|
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
|
||
|
|
try:
|
||
|
|
sock.bind((args.host, args.port))
|
||
|
|
except OSError as e:
|
||
|
|
log.error("event=bind_failed err=%s", e)
|
||
|
|
return 1
|
||
|
|
|
||
|
|
relay = Relay(sock, log)
|
||
|
|
|
||
|
|
stop_flag = {"stop": False}
|
||
|
|
|
||
|
|
def _stop_signal(_signum, _frame):
|
||
|
|
stop_flag["stop"] = True
|
||
|
|
|
||
|
|
signal.signal(signal.SIGTERM, _stop_signal)
|
||
|
|
signal.signal(signal.SIGINT, _stop_signal)
|
||
|
|
|
||
|
|
try:
|
||
|
|
while not stop_flag["stop"]:
|
||
|
|
try:
|
||
|
|
ready, _, _ = select.select([sock], [], [], SOCKET_POLL_TIMEOUT_SECONDS)
|
||
|
|
except InterruptedError:
|
||
|
|
continue
|
||
|
|
now = time.monotonic()
|
||
|
|
if ready:
|
||
|
|
try:
|
||
|
|
data, addr = sock.recvfrom(RECV_BUFFER_BYTES)
|
||
|
|
except OSError as e:
|
||
|
|
log.warning("event=recv_failed err=%s", e)
|
||
|
|
continue
|
||
|
|
relay.handle_packet(data, addr)
|
||
|
|
relay.expire_idle(now)
|
||
|
|
relay.maybe_log_stats(now)
|
||
|
|
finally:
|
||
|
|
log.info("event=shutdown")
|
||
|
|
sock.close()
|
||
|
|
|
||
|
|
return 0
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
sys.exit(main())
|