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import asyncio
import socket
import ipaddress
import struct
import secrets
import dataclasses
import enum
from ... import tools
from ... import aiotools
from ...logging import get_logger
# =====
class StunNatType(enum.Enum):
ERROR = ""
BLOCKED = "Blocked"
OPEN_INTERNET = "Open Internet"
SYMMETRIC_UDP_FW = "Symmetric UDP Firewall"
FULL_CONE_NAT = "Full Cone NAT"
RESTRICTED_NAT = "Restricted NAT"
RESTRICTED_PORT_NAT = "Restricted Port NAT"
SYMMETRIC_NAT = "Symmetric NAT"
CHANGED_ADDR_ERROR = "Error when testing on Changed-IP and Port"
@dataclasses.dataclass(frozen=True)
class StunInfo:
nat_type: StunNatType
src_ip: str
ext_ip: str
stun_ip: str
stun_port: int
@dataclasses.dataclass(frozen=True)
class _StunAddress:
ip: str
port: int
@dataclasses.dataclass(frozen=True)
class _StunResponse:
ok: bool
ext: (_StunAddress | None) = dataclasses.field(default=None)
src: (_StunAddress | None) = dataclasses.field(default=None)
changed: (_StunAddress | None) = dataclasses.field(default=None)
# =====
class Stun:
# Partially based on https://github.com/JohnVillalovos/pystun
def __init__(
self,
host: str,
port: int,
timeout: float,
retries: int,
retries_delay: float,
) -> None:
self.__host = host
self.__port = port
self.__timeout = timeout
self.__retries = retries
self.__retries_delay = retries_delay
self.__stun_ip = ""
self.__sock: (socket.socket | None) = None
async def get_info(self, src_ip: str, src_port: int) -> StunInfo:
nat_type = StunNatType.ERROR
ext_ip = ""
try:
(src_fam, _, _, _, src_addr) = (await self.__retried_getaddrinfo_udp(src_ip, src_port))[0]
stun_ips = [
stun_addr[0]
for (stun_fam, _, _, _, stun_addr) in (await self.__retried_getaddrinfo_udp(self.__host, self.__port))
if stun_fam == src_fam
]
if not stun_ips:
raise RuntimeError(f"Can't resolve {src_fam.name} address for STUN")
if not self.__stun_ip or self.__stun_ip not in stun_ips:
# On new IP, changed family, etc.
self.__stun_ip = stun_ips[0]
with socket.socket(src_fam, socket.SOCK_DGRAM) as self.__sock:
self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.__sock.settimeout(self.__timeout)
self.__sock.bind(src_addr)
(nat_type, resp) = await self.__get_nat_type(src_ip)
ext_ip = (resp.ext.ip if resp.ext is not None else "")
except Exception as err:
get_logger(0).error("Can't get STUN info: %s", tools.efmt(err))
finally:
self.__sock = None
return StunInfo(
nat_type=nat_type,
src_ip=src_ip,
ext_ip=ext_ip,
stun_ip=self.__stun_ip,
stun_port=self.__port,
)
async def __retried_getaddrinfo_udp(self, host: str, port: int) -> list:
retries = self.__retries
while True:
try:
return socket.getaddrinfo(host, port, type=socket.SOCK_DGRAM)
except Exception:
retries -= 1
if retries == 0:
raise
await asyncio.sleep(self.__retries_delay)
async def __get_nat_type(self, src_ip: str) -> tuple[StunNatType, _StunResponse]: # pylint: disable=too-many-return-statements
first = await self.__make_request("First probe", self.__stun_ip, b"")
if not first.ok:
return (StunNatType.BLOCKED, first)
req = struct.pack(">HHI", 0x0003, 0x0004, 0x00000006) # Change-Request
resp = await self.__make_request("Change request [ext_ip == src_ip]", self.__stun_ip, req)
if first.ext is not None and first.ext.ip == src_ip:
if resp.ok:
return (StunNatType.OPEN_INTERNET, resp)
return (StunNatType.SYMMETRIC_UDP_FW, resp)
if resp.ok:
return (StunNatType.FULL_CONE_NAT, resp)
if first.changed is None:
raise RuntimeError(f"Changed addr is None: {first}")
resp = await self.__make_request("Change request [ext_ip != src_ip]", first.changed, b"")
if not resp.ok:
return (StunNatType.CHANGED_ADDR_ERROR, resp)
if resp.ext == first.ext:
req = struct.pack(">HHI", 0x0003, 0x0004, 0x00000002)
resp = await self.__make_request("Change port", first.changed.ip, req)
if resp.ok:
return (StunNatType.RESTRICTED_NAT, resp)
return (StunNatType.RESTRICTED_PORT_NAT, resp)
return (StunNatType.SYMMETRIC_NAT, resp)
async def __make_request(self, ctx: str, addr: (_StunAddress | str), req: bytes) -> _StunResponse:
# TODO: Support IPv6 and RFC 5389
# The first 4 bytes of the response are the Type (2) and Length (2)
# The 5th byte is Reserved
# The 6th byte is the Family: 0x01 = IPv4, 0x02 = IPv6
# The remaining bytes are the IP address. 32 bits for IPv4 or 128 bits for
# IPv6.
# More info at: https://tools.ietf.org/html/rfc3489#section-11.2.1
# And at: https://tools.ietf.org/html/rfc5389#section-15.1
if isinstance(addr, _StunAddress):
addr_t = (addr.ip, addr.port)
else: # str
addr_t = (addr, self.__port)
# https://datatracker.ietf.org/doc/html/rfc5389#section-6
trans_id = b"\x21\x12\xA4\x42" + secrets.token_bytes(12)
(resp, error) = (b"", "")
for _ in range(self.__retries):
(resp, error) = await self.__inner_make_request(trans_id, req, addr_t)
if not error:
break
await asyncio.sleep(self.__retries_delay)
if error:
get_logger(0).error("%s: Can't perform STUN request after %d retries; last error: %s",
ctx, self.__retries, error)
return _StunResponse(ok=False)
parsed: dict[str, _StunAddress] = {}
offset = 0
remaining = len(resp)
while remaining > 0:
(attr_type, attr_len) = struct.unpack(">HH", resp[offset : offset + 4]) # noqa: E203
offset += 4
field = {
0x0001: "ext", # MAPPED-ADDRESS
0x0020: "ext", # XOR-MAPPED-ADDRESS
0x0004: "src", # SOURCE-ADDRESS
0x0005: "changed", # CHANGED-ADDRESS
}.get(attr_type)
if field is not None:
parsed[field] = self.__parse_address(resp[offset:], (trans_id if attr_type == 0x0020 else b""))
offset += attr_len
remaining -= (4 + attr_len)
return _StunResponse(ok=True, **parsed)
async def __inner_make_request(self, trans_id: bytes, req: bytes, addr: tuple[str, int]) -> tuple[bytes, str]:
assert self.__sock is not None
req = struct.pack(">HH", 0x0001, len(req)) + trans_id + req # Bind Request
try:
await aiotools.run_async(self.__sock.sendto, req, addr)
except Exception as err:
return (b"", f"Send error: {tools.efmt(err)}")
try:
resp = (await aiotools.run_async(self.__sock.recvfrom, 2048))[0]
except Exception as err:
return (b"", f"Recv error: {tools.efmt(err)}")
(response_type, payload_len) = struct.unpack(">HH", resp[:4])
if response_type != 0x0101:
return (b"", f"Invalid response type: {response_type:#06x}")
if trans_id != resp[4:20]:
return (b"", "Transaction ID mismatch")
return (resp[20 : 20 + payload_len], "") # noqa: E203
def __parse_address(self, data: bytes, trans_id: bytes) -> _StunAddress:
family = data[1]
port = struct.unpack(">H", self.__trans_xor(data[2:4], trans_id))[0]
if family == 0x01:
return _StunAddress(str(ipaddress.IPv4Address(self.__trans_xor(data[4:8], trans_id))), port)
elif family == 0x02:
return _StunAddress(str(ipaddress.IPv6Address(self.__trans_xor(data[4:20], trans_id))), port)
raise RuntimeError(f"Unknown family; received: {family}")
def __trans_xor(self, data: bytes, trans_id: bytes) -> bytes:
if len(trans_id) == 0:
return data
assert len(data) <= len(trans_id)
return bytes(byte ^ trans_id[index] for (index, byte) in enumerate(data))
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