import asyncio
import socket
from typing import Any, Dict, List, Optional, Type, Union
from .abc import AbstractResolver
from .helpers import get_running_loop
__all__ = ("ThreadedResolver", "AsyncResolver", "DefaultResolver")
try:
import aiodns
# aiodns_default = hasattr(aiodns.DNSResolver, 'gethostbyname')
except ImportError: # pragma: no cover
aiodns = None
aiodns_default = False
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 = get_running_loop(loop)
async def resolve(
self, hostname: str, port: int = 0, family: int = socket.AF_INET
) -> List[Dict[str, Any]]:
infos = await self._loop.getaddrinfo(
hostname,
port,
type=socket.SOCK_STREAM,
family=family,
flags=socket.AI_ADDRCONFIG,
)
hosts = []
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]:
# 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.
host, _port = socket.getnameinfo(
address, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
)
port = int(_port)
else:
host, port = address[:2]
else: # IPv4
assert family == socket.AF_INET
host, port = address # type: ignore[misc]
hosts.append(
{
"hostname": hostname,
"host": host,
"port": port,
"family": family,
"proto": proto,
"flags": socket.AI_NUMERICHOST | socket.AI_NUMERICSERV,
}
)
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._loop = get_running_loop(loop)
self._resolver = aiodns.DNSResolver(*args, loop=loop, **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: int = socket.AF_INET
) -> List[Dict[str, Any]]:
try:
resp = await self._resolver.gethostbyname(host, family)
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 address in resp.addresses:
hosts.append(
{
"hostname": host,
"host": address,
"port": port,
"family": family,
"proto": 0,
"flags": socket.AI_NUMERICHOST | socket.AI_NUMERICSERV,
}
)
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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