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import asyncio
import socket
import sys
from typing import Any, Dict, List, Optional, Tuple, Type, Union
from .abc import AbstractResolver, ResolveResult
__all__ = ("ThreadedResolver", "AsyncResolver", "DefaultResolver")
try:
import aiodns
aiodns_default = hasattr(aiodns.DNSResolver, "getaddrinfo")
except ImportError: # pragma: no cover
aiodns = None # type: ignore[assignment]
aiodns_default = False
_NUMERIC_SOCKET_FLAGS = socket.AI_NUMERICHOST | socket.AI_NUMERICSERV
_SUPPORTS_SCOPE_ID = sys.version_info >= (3, 9, 0)
class ThreadedResolver(AbstractResolver):
"""Threaded resolver.
Uses an Executor for synchronous getaddrinfo() calls.
concurrent.futures.ThreadPoolExecutor is used by default.
"""
def __init__(self, loop: Optional[asyncio.AbstractEventLoop] = None) -> None:
self._loop = loop or asyncio.get_running_loop()
async def resolve(
self, host: str, port: int = 0, family: socket.AddressFamily = socket.AF_INET
) -> List[ResolveResult]:
infos = await self._loop.getaddrinfo(
host,
port,
type=socket.SOCK_STREAM,
family=family,
flags=socket.AI_ADDRCONFIG,
)
hosts: List[ResolveResult] = []
for family, _, proto, _, address in infos:
if family == socket.AF_INET6:
if len(address) < 3:
# IPv6 is not supported by Python build,
# or IPv6 is not enabled in the host
continue
if address[3] and _SUPPORTS_SCOPE_ID:
# This is essential for link-local IPv6 addresses.
# LL IPv6 is a VERY rare case. Strictly speaking, we should use
# getnameinfo() unconditionally, but performance makes sense.
resolved_host, _port = await self._loop.getnameinfo(
address, _NUMERIC_SOCKET_FLAGS
)
port = int(_port)
else:
resolved_host, port = address[:2]
else: # IPv4
assert family == socket.AF_INET
resolved_host, port = address # type: ignore[misc]
hosts.append(
ResolveResult(
hostname=host,
host=resolved_host,
port=port,
family=family,
proto=proto,
flags=_NUMERIC_SOCKET_FLAGS,
)
)
return hosts
async def close(self) -> None:
pass
class AsyncResolver(AbstractResolver):
"""Use the `aiodns` package to make asynchronous DNS lookups"""
def __init__(
self,
loop: Optional[asyncio.AbstractEventLoop] = None,
*args: Any,
**kwargs: Any
) -> None:
if aiodns is None:
raise RuntimeError("Resolver requires aiodns library")
self._resolver = aiodns.DNSResolver(*args, **kwargs)
if not hasattr(self._resolver, "gethostbyname"):
# aiodns 1.1 is not available, fallback to DNSResolver.query
self.resolve = self._resolve_with_query # type: ignore
async def resolve(
self, host: str, port: int = 0, family: socket.AddressFamily = socket.AF_INET
) -> List[ResolveResult]:
try:
resp = await self._resolver.getaddrinfo(
host,
port=port,
type=socket.SOCK_STREAM,
family=family,
flags=socket.AI_ADDRCONFIG,
)
except aiodns.error.DNSError as exc:
msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
raise OSError(msg) from exc
hosts: List[ResolveResult] = []
for node in resp.nodes:
address: Union[Tuple[bytes, int], Tuple[bytes, int, int, int]] = node.addr
family = node.family
if family == socket.AF_INET6:
if len(address) > 3 and address[3] and _SUPPORTS_SCOPE_ID:
# This is essential for link-local IPv6 addresses.
# LL IPv6 is a VERY rare case. Strictly speaking, we should use
# getnameinfo() unconditionally, but performance makes sense.
result = await self._resolver.getnameinfo(
(address[0].decode("ascii"), *address[1:]),
_NUMERIC_SOCKET_FLAGS,
)
resolved_host = result.node
else:
resolved_host = address[0].decode("ascii")
port = address[1]
else: # IPv4
assert family == socket.AF_INET
resolved_host = address[0].decode("ascii")
port = address[1]
hosts.append(
ResolveResult(
hostname=host,
host=resolved_host,
port=port,
family=family,
proto=0,
flags=_NUMERIC_SOCKET_FLAGS,
)
)
if not hosts:
raise OSError("DNS lookup failed")
return hosts
async def _resolve_with_query(
self, host: str, port: int = 0, family: int = socket.AF_INET
) -> List[Dict[str, Any]]:
if family == socket.AF_INET6:
qtype = "AAAA"
else:
qtype = "A"
try:
resp = await self._resolver.query(host, qtype)
except aiodns.error.DNSError as exc:
msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
raise OSError(msg) from exc
hosts = []
for rr in resp:
hosts.append(
{
"hostname": host,
"host": rr.host,
"port": port,
"family": family,
"proto": 0,
"flags": socket.AI_NUMERICHOST,
}
)
if not hosts:
raise OSError("DNS lookup failed")
return hosts
async def close(self) -> None:
self._resolver.cancel()
_DefaultType = Type[Union[AsyncResolver, ThreadedResolver]]
DefaultResolver: _DefaultType = AsyncResolver if aiodns_default else ThreadedResolver
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