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# -*- test-case-name: twisted.test.test_tcp -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Various asynchronous TCP/IP classes.
End users shouldn't use this module directly - use the reactor APIs instead.
"""
import os
# System Imports
import socket
import struct
import sys
from typing import Callable, ClassVar, List, Optional, Protocol
from zope.interface import Interface, implementer
import attr
from twisted.internet.interfaces import (
IHalfCloseableProtocol,
IListeningPort,
ISystemHandle,
ITCPTransport,
)
from twisted.logger import ILogObserver, LogEvent, Logger
from twisted.python import deprecate, versions
from twisted.python.compat import lazyByteSlice
from twisted.python.runtime import platformType
try:
# Try to get the memory BIO based startTLS implementation, available since
# pyOpenSSL 0.10
from twisted.internet._newtls import (
ClientMixin as _TLSClientMixin,
ConnectionMixin as _TLSConnectionMixin,
ServerMixin as _TLSServerMixin,
)
from twisted.internet.interfaces import ITLSTransport
except ImportError:
# There is no version of startTLS available
ITLSTransport = Interface # type: ignore[misc,assignment]
class _TLSConnectionMixin: # type: ignore[no-redef]
TLS = False
class _TLSClientMixin: # type: ignore[no-redef]
pass
class _TLSServerMixin: # type: ignore[no-redef]
pass
if platformType == "win32":
# no such thing as WSAEPERM or error code 10001
# according to winsock.h or MSDN
EPERM = object()
from errno import ( # type: ignore[attr-defined]
WSAEALREADY as EALREADY,
WSAEINPROGRESS as EINPROGRESS,
WSAEINVAL as EINVAL,
WSAEISCONN as EISCONN,
WSAEMFILE as EMFILE,
WSAENOBUFS as ENOBUFS,
WSAEWOULDBLOCK as EWOULDBLOCK,
)
# No such thing as WSAENFILE, either.
ENFILE = object()
# Nor ENOMEM
ENOMEM = object()
EAGAIN = EWOULDBLOCK
from errno import WSAECONNRESET as ECONNABORTED # type: ignore[attr-defined]
from twisted.python.win32 import formatError as strerror
else:
from errno import EPERM
from errno import EINVAL
from errno import EWOULDBLOCK
from errno import EINPROGRESS
from errno import EALREADY
from errno import EISCONN
from errno import ENOBUFS
from errno import EMFILE
from errno import ENFILE
from errno import ENOMEM
from errno import EAGAIN
from errno import ECONNABORTED
from os import strerror
from errno import errorcode
# Twisted Imports
from twisted.internet import abstract, address, base, error, fdesc, main
from twisted.internet.error import CannotListenError
from twisted.internet.protocol import Protocol
from twisted.internet.task import deferLater
from twisted.python import failure, log, reflect
from twisted.python.util import untilConcludes
# Not all platforms have, or support, this flag.
_AI_NUMERICSERV = getattr(socket, "AI_NUMERICSERV", 0)
def _getrealname(addr):
"""
Return a 2-tuple of socket IP and port for IPv4 and a 4-tuple of
socket IP, port, flowInfo, and scopeID for IPv6. For IPv6, it
returns the interface portion (the part after the %) as a part of
the IPv6 address, which Python 3.7+ does not include.
@param addr: A 2-tuple for IPv4 information or a 4-tuple for IPv6
information.
"""
if len(addr) == 4:
# IPv6
host = socket.getnameinfo(addr, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV)[
0
]
return tuple([host] + list(addr[1:]))
else:
return addr[:2]
def _getpeername(skt):
"""
See L{_getrealname}.
"""
return _getrealname(skt.getpeername())
def _getsockname(skt):
"""
See L{_getrealname}.
"""
return _getrealname(skt.getsockname())
class _SocketCloser:
"""
@ivar _shouldShutdown: Set to C{True} if C{shutdown} should be called
before calling C{close} on the underlying socket.
@type _shouldShutdown: C{bool}
"""
_shouldShutdown = True
def _closeSocket(self, orderly):
# The call to shutdown() before close() isn't really necessary, because
# we set FD_CLOEXEC now, which will ensure this is the only process
# holding the FD, thus ensuring close() really will shutdown the TCP
# socket. However, do it anyways, just to be safe.
skt = self.socket
try:
if orderly:
if self._shouldShutdown:
skt.shutdown(2)
else:
# Set SO_LINGER to 1,0 which, by convention, causes a
# connection reset to be sent when close is called,
# instead of the standard FIN shutdown sequence.
self.socket.setsockopt(
socket.SOL_SOCKET, socket.SO_LINGER, struct.pack("ii", 1, 0)
)
except OSError:
pass
try:
skt.close()
except OSError:
pass
class _AbortingMixin:
"""
Common implementation of C{abortConnection}.
@ivar _aborting: Set to C{True} when C{abortConnection} is called.
@type _aborting: C{bool}
"""
_aborting = False
def abortConnection(self):
"""
Aborts the connection immediately, dropping any buffered data.
@since: 11.1
"""
if self.disconnected or self._aborting:
return
self._aborting = True
self.stopReading()
self.stopWriting()
self.doRead = lambda *args, **kwargs: None
self.doWrite = lambda *args, **kwargs: None
self.reactor.callLater(
0, self.connectionLost, failure.Failure(error.ConnectionAborted())
)
@implementer(ITLSTransport, ITCPTransport, ISystemHandle)
class Connection(
_TLSConnectionMixin, abstract.FileDescriptor, _SocketCloser, _AbortingMixin
):
"""
Superclass of all socket-based FileDescriptors.
This is an abstract superclass of all objects which represent a TCP/IP
connection based socket.
@ivar logstr: prefix used when logging events related to this connection.
@type logstr: C{str}
"""
def __init__(self, skt, protocol, reactor=None):
abstract.FileDescriptor.__init__(self, reactor=reactor)
self.socket = skt
self.socket.setblocking(0)
self.fileno = skt.fileno
self.protocol = protocol
def getHandle(self):
"""Return the socket for this connection."""
return self.socket
def doRead(self):
"""Calls self.protocol.dataReceived with all available data.
This reads up to self.bufferSize bytes of data from its socket, then
calls self.dataReceived(data) to process it. If the connection is not
lost through an error in the physical recv(), this function will return
the result of the dataReceived call.
"""
try:
data = self.socket.recv(self.bufferSize)
except OSError as se:
if se.args[0] == EWOULDBLOCK:
return
else:
return main.CONNECTION_LOST
return self._dataReceived(data)
def _dataReceived(self, data):
if not data:
return main.CONNECTION_DONE
rval = self.protocol.dataReceived(data)
if rval is not None:
offender = self.protocol.dataReceived
warningFormat = (
"Returning a value other than None from %(fqpn)s is "
"deprecated since %(version)s."
)
warningString = deprecate.getDeprecationWarningString(
offender, versions.Version("Twisted", 11, 0, 0), format=warningFormat
)
deprecate.warnAboutFunction(offender, warningString)
return rval
def writeSomeData(self, data):
"""
Write as much as possible of the given data to this TCP connection.
This sends up to C{self.SEND_LIMIT} bytes from C{data}. If the
connection is lost, an exception is returned. Otherwise, the number
of bytes successfully written is returned.
"""
# Limit length of buffer to try to send, because some OSes are too
# stupid to do so themselves (ahem windows)
limitedData = lazyByteSlice(data, 0, self.SEND_LIMIT)
try:
return untilConcludes(self.socket.send, limitedData)
except OSError as se:
if se.args[0] in (EWOULDBLOCK, ENOBUFS):
return 0
else:
return main.CONNECTION_LOST
def _closeWriteConnection(self):
try:
self.socket.shutdown(1)
except OSError:
pass
p = IHalfCloseableProtocol(self.protocol, None)
if p:
try:
p.writeConnectionLost()
except BaseException:
f = failure.Failure()
log.err()
self.connectionLost(f)
def readConnectionLost(self, reason):
p = IHalfCloseableProtocol(self.protocol, None)
if p:
try:
p.readConnectionLost()
except BaseException:
log.err()
self.connectionLost(failure.Failure())
else:
self.connectionLost(reason)
def connectionLost(self, reason):
"""See abstract.FileDescriptor.connectionLost()."""
# Make sure we're not called twice, which can happen e.g. if
# abortConnection() is called from protocol's dataReceived and then
# code immediately after throws an exception that reaches the
# reactor. We can't rely on "disconnected" attribute for this check
# since twisted.internet._oldtls does evil things to it:
if not hasattr(self, "socket"):
return
abstract.FileDescriptor.connectionLost(self, reason)
self._closeSocket(not reason.check(error.ConnectionAborted))
protocol = self.protocol
del self.protocol
del self.socket
del self.fileno
protocol.connectionLost(reason)
logstr = "Uninitialized"
def logPrefix(self):
"""Return the prefix to log with when I own the logging thread."""
return self.logstr
def getTcpNoDelay(self):
return bool(self.socket.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY))
def setTcpNoDelay(self, enabled):
self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, enabled)
def getTcpKeepAlive(self):
return bool(self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE))
def setTcpKeepAlive(self, enabled):
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, enabled)
class _BaseBaseClient:
"""
Code shared with other (non-POSIX) reactors for management of general
outgoing connections.
Requirements upon subclasses are documented as instance variables rather
than abstract methods, in order to avoid MRO confusion, since this base is
mixed in to unfortunately weird and distinctive multiple-inheritance
hierarchies and many of these attributes are provided by peer classes
rather than descendant classes in those hierarchies.
@ivar addressFamily: The address family constant (C{socket.AF_INET},
C{socket.AF_INET6}, C{socket.AF_UNIX}) of the underlying socket of this
client connection.
@type addressFamily: C{int}
@ivar socketType: The socket type constant (C{socket.SOCK_STREAM} or
C{socket.SOCK_DGRAM}) of the underlying socket.
@type socketType: C{int}
@ivar _requiresResolution: A flag indicating whether the address of this
client will require name resolution. C{True} if the hostname of said
address indicates a name that must be resolved by hostname lookup,
C{False} if it indicates an IP address literal.
@type _requiresResolution: C{bool}
@cvar _commonConnection: Subclasses must provide this attribute, which
indicates the L{Connection}-alike class to invoke C{__init__} and
C{connectionLost} on.
@type _commonConnection: C{type}
@ivar _stopReadingAndWriting: Subclasses must implement in order to remove
this transport from its reactor's notifications in response to a
terminated connection attempt.
@type _stopReadingAndWriting: 0-argument callable returning L{None}
@ivar _closeSocket: Subclasses must implement in order to close the socket
in response to a terminated connection attempt.
@type _closeSocket: 1-argument callable; see L{_SocketCloser._closeSocket}
@ivar _collectSocketDetails: Clean up references to the attached socket in
its underlying OS resource (such as a file descriptor or file handle),
as part of post connection-failure cleanup.
@type _collectSocketDetails: 0-argument callable returning L{None}.
@ivar reactor: The class pointed to by C{_commonConnection} should set this
attribute in its constructor.
@type reactor: L{twisted.internet.interfaces.IReactorTime},
L{twisted.internet.interfaces.IReactorCore},
L{twisted.internet.interfaces.IReactorFDSet}
"""
addressFamily = socket.AF_INET
socketType = socket.SOCK_STREAM
def _finishInit(self, whenDone, skt, error, reactor):
"""
Called by subclasses to continue to the stage of initialization where
the socket connect attempt is made.
@param whenDone: A 0-argument callable to invoke once the connection is
set up. This is L{None} if the connection could not be prepared
due to a previous error.
@param skt: The socket object to use to perform the connection.
@type skt: C{socket._socketobject}
@param error: The error to fail the connection with.
@param reactor: The reactor to use for this client.
@type reactor: L{twisted.internet.interfaces.IReactorTime}
"""
if whenDone:
self._commonConnection.__init__(self, skt, None, reactor)
reactor.callLater(0, whenDone)
else:
reactor.callLater(0, self.failIfNotConnected, error)
def resolveAddress(self):
"""
Resolve the name that was passed to this L{_BaseBaseClient}, if
necessary, and then move on to attempting the connection once an
address has been determined. (The connection will be attempted
immediately within this function if either name resolution can be
synchronous or the address was an IP address literal.)
@note: You don't want to call this method from outside, as it won't do
anything useful; it's just part of the connection bootstrapping
process. Also, although this method is on L{_BaseBaseClient} for
historical reasons, it's not used anywhere except for L{Client}
itself.
@return: L{None}
"""
if self._requiresResolution:
d = self.reactor.resolve(self.addr[0])
d.addCallback(lambda n: (n,) + self.addr[1:])
d.addCallbacks(self._setRealAddress, self.failIfNotConnected)
else:
self._setRealAddress(self.addr)
def _setRealAddress(self, address):
"""
Set the resolved address of this L{_BaseBaseClient} and initiate the
connection attempt.
@param address: Depending on whether this is an IPv4 or IPv6 connection
attempt, a 2-tuple of C{(host, port)} or a 4-tuple of C{(host,
port, flow, scope)}. At this point it is a fully resolved address,
and the 'host' portion will always be an IP address, not a DNS
name.
"""
if len(address) == 4:
# IPv6, make sure we have the scopeID associated
hostname = socket.getnameinfo(
address, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
)[0]
self.realAddress = tuple([hostname] + list(address[1:]))
else:
self.realAddress = address
self.doConnect()
def failIfNotConnected(self, err):
"""
Generic method called when the attempts to connect failed. It basically
cleans everything it can: call connectionFailed, stop read and write,
delete socket related members.
"""
if self.connected or self.disconnected or not hasattr(self, "connector"):
return
self._stopReadingAndWriting()
try:
self._closeSocket(True)
except AttributeError:
pass
else:
self._collectSocketDetails()
self.connector.connectionFailed(failure.Failure(err))
del self.connector
def stopConnecting(self):
"""
If a connection attempt is still outstanding (i.e. no connection is
yet established), immediately stop attempting to connect.
"""
self.failIfNotConnected(error.UserError())
def connectionLost(self, reason):
"""
Invoked by lower-level logic when it's time to clean the socket up.
Depending on the state of the connection, either inform the attached
L{Connector} that the connection attempt has failed, or inform the
connected L{IProtocol} that the established connection has been lost.
@param reason: the reason that the connection was terminated
@type reason: L{Failure}
"""
if not self.connected:
self.failIfNotConnected(error.ConnectError(string=reason))
else:
self._commonConnection.connectionLost(self, reason)
self.connector.connectionLost(reason)
class BaseClient(_BaseBaseClient, _TLSClientMixin, Connection):
"""
A base class for client TCP (and similar) sockets.
@ivar realAddress: The address object that will be used for socket.connect;
this address is an address tuple (the number of elements dependent upon
the address family) which does not contain any names which need to be
resolved.
@type realAddress: C{tuple}
@ivar _base: L{Connection}, which is the base class of this class which has
all of the useful file descriptor methods. This is used by
L{_TLSServerMixin} to call the right methods to directly manipulate the
transport, as is necessary for writing TLS-encrypted bytes (whereas
those methods on L{Server} will go through another layer of TLS if it
has been enabled).
"""
_base = Connection
_commonConnection = Connection
def _stopReadingAndWriting(self):
"""
Implement the POSIX-ish (i.e.
L{twisted.internet.interfaces.IReactorFDSet}) method of detaching this
socket from the reactor for L{_BaseBaseClient}.
"""
if hasattr(self, "reactor"):
# this doesn't happen if we failed in __init__
self.stopReading()
self.stopWriting()
def _collectSocketDetails(self):
"""
Clean up references to the socket and its file descriptor.
@see: L{_BaseBaseClient}
"""
del self.socket, self.fileno
def createInternetSocket(self):
"""(internal) Create a non-blocking socket using
self.addressFamily, self.socketType.
"""
s = socket.socket(self.addressFamily, self.socketType)
s.setblocking(0)
fdesc._setCloseOnExec(s.fileno())
return s
def doConnect(self):
"""
Initiate the outgoing connection attempt.
@note: Applications do not need to call this method; it will be invoked
internally as part of L{IReactorTCP.connectTCP}.
"""
self.doWrite = self.doConnect
self.doRead = self.doConnect
if not hasattr(self, "connector"):
# this happens when connection failed but doConnect
# was scheduled via a callLater in self._finishInit
return
err = self.socket.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
if err:
self.failIfNotConnected(error.getConnectError((err, strerror(err))))
return
# doConnect gets called twice. The first time we actually need to
# start the connection attempt. The second time we don't really
# want to (SO_ERROR above will have taken care of any errors, and if
# it reported none, the mere fact that doConnect was called again is
# sufficient to indicate that the connection has succeeded), but it
# is not /particularly/ detrimental to do so. This should get
# cleaned up some day, though.
try:
connectResult = self.socket.connect_ex(self.realAddress)
except OSError as se:
connectResult = se.args[0]
if connectResult:
if connectResult == EISCONN:
pass
# on Windows EINVAL means sometimes that we should keep trying:
# http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/connect_2.asp
elif (connectResult in (EWOULDBLOCK, EINPROGRESS, EALREADY)) or (
connectResult == EINVAL and platformType == "win32"
):
self.startReading()
self.startWriting()
return
else:
self.failIfNotConnected(
error.getConnectError((connectResult, strerror(connectResult)))
)
return
# If I have reached this point without raising or returning, that means
# that the socket is connected.
del self.doWrite
del self.doRead
# we first stop and then start, to reset any references to the old doRead
self.stopReading()
self.stopWriting()
self._connectDone()
def _connectDone(self):
"""
This is a hook for when a connection attempt has succeeded.
Here, we build the protocol from the
L{twisted.internet.protocol.ClientFactory} that was passed in, compute
a log string, begin reading so as to send traffic to the newly built
protocol, and finally hook up the protocol itself.
This hook is overridden by L{ssl.Client} to initiate the TLS protocol.
"""
self.protocol = self.connector.buildProtocol(self.getPeer())
self.connected = 1
logPrefix = self._getLogPrefix(self.protocol)
self.logstr = "%s,client" % logPrefix
if self.protocol is None:
# Factory.buildProtocol is allowed to return None. In that case,
# make up a protocol to satisfy the rest of the implementation;
# connectionLost is going to be called on something, for example.
# This is easier than adding special case support for a None
# protocol throughout the rest of the transport implementation.
self.protocol = Protocol()
# But dispose of the connection quickly.
self.loseConnection()
else:
self.startReading()
self.protocol.makeConnection(self)
_NUMERIC_ONLY = socket.AI_NUMERICHOST | _AI_NUMERICSERV
def _resolveIPv6(ip, port):
"""
Resolve an IPv6 literal into an IPv6 address.
This is necessary to resolve any embedded scope identifiers to the relevant
C{sin6_scope_id} for use with C{socket.connect()}, C{socket.listen()}, or
C{socket.bind()}; see U{RFC 3493 <https://tools.ietf.org/html/rfc3493>} for
more information.
@param ip: An IPv6 address literal.
@type ip: C{str}
@param port: A port number.
@type port: C{int}
@return: a 4-tuple of C{(host, port, flow, scope)}, suitable for use as an
IPv6 address.
@raise socket.gaierror: if either the IP or port is not numeric as it
should be.
"""
return socket.getaddrinfo(ip, port, 0, 0, 0, _NUMERIC_ONLY)[0][4]
class _BaseTCPClient:
"""
Code shared with other (non-POSIX) reactors for management of outgoing TCP
connections (both TCPv4 and TCPv6).
@note: In order to be functional, this class must be mixed into the same
hierarchy as L{_BaseBaseClient}. It would subclass L{_BaseBaseClient}
directly, but the class hierarchy here is divided in strange ways out
of the need to share code along multiple axes; specifically, with the
IOCP reactor and also with UNIX clients in other reactors.
@ivar _addressType: The Twisted _IPAddress implementation for this client
@type _addressType: L{IPv4Address} or L{IPv6Address}
@ivar connector: The L{Connector} which is driving this L{_BaseTCPClient}'s
connection attempt.
@ivar addr: The address that this socket will be connecting to.
@type addr: If IPv4, a 2-C{tuple} of C{(str host, int port)}. If IPv6, a
4-C{tuple} of (C{str host, int port, int ignored, int scope}).
@ivar createInternetSocket: Subclasses must implement this as a method to
create a python socket object of the appropriate address family and
socket type.
@type createInternetSocket: 0-argument callable returning
C{socket._socketobject}.
"""
_addressType = address.IPv4Address
def __init__(self, host, port, bindAddress, connector, reactor=None):
# BaseClient.__init__ is invoked later
self.connector = connector
self.addr = (host, port)
whenDone = self.resolveAddress
err = None
skt = None
if abstract.isIPAddress(host):
self._requiresResolution = False
elif abstract.isIPv6Address(host):
self._requiresResolution = False
self.addr = _resolveIPv6(host, port)
self.addressFamily = socket.AF_INET6
self._addressType = address.IPv6Address
else:
self._requiresResolution = True
try:
skt = self.createInternetSocket()
except OSError as se:
err = error.ConnectBindError(se.args[0], se.args[1])
whenDone = None
if whenDone and bindAddress is not None:
try:
if abstract.isIPv6Address(bindAddress[0]):
bindinfo = _resolveIPv6(*bindAddress)
else:
bindinfo = bindAddress
skt.bind(bindinfo)
except OSError as se:
err = error.ConnectBindError(se.args[0], se.args[1])
whenDone = None
self._finishInit(whenDone, skt, err, reactor)
def getHost(self):
"""
Returns an L{IPv4Address} or L{IPv6Address}.
This indicates the address from which I am connecting.
"""
return self._addressType("TCP", *_getsockname(self.socket))
def getPeer(self):
"""
Returns an L{IPv4Address} or L{IPv6Address}.
This indicates the address that I am connected to.
"""
return self._addressType("TCP", *self.realAddress)
def __repr__(self) -> str:
s = f"<{self.__class__} to {self.addr} at {id(self):x}>"
return s
class Client(_BaseTCPClient, BaseClient):
"""
A transport for a TCP protocol; either TCPv4 or TCPv6.
Do not create these directly; use L{IReactorTCP.connectTCP}.
"""
class Server(_TLSServerMixin, Connection):
"""
Serverside socket-stream connection class.
This is a serverside network connection transport; a socket which came from
an accept() on a server.
@ivar _base: L{Connection}, which is the base class of this class which has
all of the useful file descriptor methods. This is used by
L{_TLSServerMixin} to call the right methods to directly manipulate the
transport, as is necessary for writing TLS-encrypted bytes (whereas
those methods on L{Server} will go through another layer of TLS if it
has been enabled).
"""
_base = Connection
_addressType = address.IPv4Address
def __init__(self, sock, protocol, client, server, sessionno, reactor):
"""
Server(sock, protocol, client, server, sessionno)
Initialize it with a socket, a protocol, a descriptor for my peer (a
tuple of host, port describing the other end of the connection), an
instance of Port, and a session number.
"""
Connection.__init__(self, sock, protocol, reactor)
if len(client) != 2:
self._addressType = address.IPv6Address
self.server = server
self.client = client
self.sessionno = sessionno
self.hostname = client[0]
logPrefix = self._getLogPrefix(self.protocol)
self.logstr = f"{logPrefix},{sessionno},{self.hostname}"
if self.server is not None:
self.repstr = "<{} #{} on {}>".format(
self.protocol.__class__.__name__,
self.sessionno,
self.server._realPortNumber,
)
self.startReading()
self.connected = 1
def __repr__(self) -> str:
"""
A string representation of this connection.
"""
return self.repstr
@classmethod
def _fromConnectedSocket(cls, fileDescriptor, addressFamily, factory, reactor):
"""
Create a new L{Server} based on an existing connected I{SOCK_STREAM}
socket.
Arguments are the same as to L{Server.__init__}, except where noted.
@param fileDescriptor: An integer file descriptor associated with a
connected socket. The socket must be in non-blocking mode. Any
additional attributes desired, such as I{FD_CLOEXEC}, must also be
set already.
@param addressFamily: The address family (sometimes called I{domain})
of the existing socket. For example, L{socket.AF_INET}.
@return: A new instance of C{cls} wrapping the socket given by
C{fileDescriptor}.
"""
addressType = address.IPv4Address
if addressFamily == socket.AF_INET6:
addressType = address.IPv6Address
skt = socket.fromfd(fileDescriptor, addressFamily, socket.SOCK_STREAM)
addr = _getpeername(skt)
protocolAddr = addressType("TCP", *addr)
localPort = skt.getsockname()[1]
protocol = factory.buildProtocol(protocolAddr)
if protocol is None:
skt.close()
return
self = cls(skt, protocol, addr, None, addr[1], reactor)
self.repstr = "<{} #{} on {}>".format(
self.protocol.__class__.__name__,
self.sessionno,
localPort,
)
protocol.makeConnection(self)
return self
def getHost(self):
"""
Returns an L{IPv4Address} or L{IPv6Address}.
This indicates the server's address.
"""
addr = _getsockname(self.socket)
return self._addressType("TCP", *addr)
def getPeer(self):
"""
Returns an L{IPv4Address} or L{IPv6Address}.
This indicates the client's address.
"""
return self._addressType("TCP", *self.client)
class _IFileDescriptorReservation(Interface):
"""
An open file that represents an emergency reservation in the
process' file descriptor table. If L{Port} encounters C{EMFILE}
on C{accept(2)}, it can close this file descriptor, retry the
C{accept} so that the incoming connection occupies this file
descriptor's space, and then close that connection and reopen this
one.
Calling L{_IFileDescriptorReservation.reserve} attempts to open
the reserve file descriptor if it is not already open.
L{_IFileDescriptorReservation.available} returns L{True} if the
underlying file is open and its descriptor claimed.
L{_IFileDescriptorReservation} instances are context managers;
entering them releases the underlying file descriptor, while
exiting them attempts to reacquire it. The block can take
advantage of the free slot in the process' file descriptor table
accept and close a client connection.
Because another thread might open a file descriptor between the
time the context manager is entered and the time C{accept} is
called, opening the reserve descriptor is best-effort only.
"""
def available():
"""
Is the reservation available?
@return: L{True} if the reserved file descriptor is open and
can thus be closed to allow a new file to be opened in its
place; L{False} if it is not open.
"""
def reserve():
"""
Attempt to open the reserved file descriptor; if this fails
because of C{EMFILE}, internal state is reset so that another
reservation attempt can be made.
@raises Exception: Any exception except an L{OSError} whose
errno is L{EMFILE}.
"""
def __enter__():
"""
Release the underlying file descriptor so that code within the
context manager can open a new file.
"""
def __exit__(excType, excValue, traceback):
"""
Attempt to re-open the reserved file descriptor. See
L{reserve} for caveats.
@param excType: See L{object.__exit__}
@param excValue: See L{object.__exit__}
@param traceback: See L{object.__exit__}
"""
class _HasClose(Protocol):
def close(self) -> object:
...
@implementer(_IFileDescriptorReservation)
@attr.s(auto_attribs=True)
class _FileDescriptorReservation:
"""
L{_IFileDescriptorReservation} implementation.
@ivar fileFactory: A factory that will be called to reserve a
file descriptor.
@type fileFactory: A L{callable} that accepts no arguments and
returns an object with a C{close} method.
"""
_log: ClassVar[Logger] = Logger()
_fileFactory: Callable[[], _HasClose]
_fileDescriptor: Optional[_HasClose] = attr.ib(init=False, default=None)
def available(self):
"""
See L{_IFileDescriptorReservation.available}.
@return: L{True} if the reserved file descriptor is open and
can thus be closed to allow a new file to be opened in its
place; L{False} if it is not open.
"""
return self._fileDescriptor is not None
def reserve(self):
"""
See L{_IFileDescriptorReservation.reserve}.
"""
if self._fileDescriptor is None:
try:
fileDescriptor = self._fileFactory()
except OSError as e:
if e.errno == EMFILE:
self._log.failure(
"Could not reserve EMFILE recovery file descriptor."
)
else:
raise
else:
self._fileDescriptor = fileDescriptor
def __enter__(self):
"""
See L{_IFileDescriptorReservation.__enter__}.
"""
if self._fileDescriptor is None:
raise RuntimeError("No file reserved. Have you called my reserve method?")
self._fileDescriptor.close()
self._fileDescriptor = None
def __exit__(self, excType, excValue, traceback):
"""
See L{_IFileDescriptorReservation.__exit__}.
"""
try:
self.reserve()
except Exception:
self._log.failure("Could not re-reserve EMFILE recovery file descriptor.")
@implementer(_IFileDescriptorReservation)
class _NullFileDescriptorReservation:
"""
A null implementation of L{_IFileDescriptorReservation}.
"""
def available(self):
"""
The reserved file is never available. See
L{_IFileDescriptorReservation.available}.
@return: L{False}
"""
return False
def reserve(self):
"""
Do nothing. See L{_IFileDescriptorReservation.reserve}.
"""
def __enter__(self):
"""
Do nothing. See L{_IFileDescriptorReservation.__enter__}
@return: L{False}
"""
def __exit__(self, excType, excValue, traceback):
"""
Do nothing. See L{_IFileDescriptorReservation.__exit__}.
@param excType: See L{object.__exit__}
@param excValue: See L{object.__exit__}
@param traceback: See L{object.__exit__}
"""
# Don't keep a reserve file descriptor for coping with file descriptor
# exhaustion on Windows.
# WSAEMFILE occurs when a process has run out of memory, not when a
# specific limit has been reached. Windows sockets are handles, which
# differ from UNIX's file descriptors in that they can refer to any
# "named kernel object", including user interface resources like menu
# and icons. The generality of handles results in a much higher limit
# than UNIX imposes on file descriptors: a single Windows process can
# allocate up to 16,777,216 handles. Because they're indexes into a
# three level table whose upper two layers are allocated from
# swappable pages, handles compete for heap space with other kernel
# objects, not with each other. Closing a given socket handle may not
# release enough memory to allow the process to make progress.
#
# This fundamental difference between file descriptors and handles
# makes a reserve file descriptor useless on Windows. Note that other
# event loops, such as libuv and libevent, also do not special case
# WSAEMFILE.
#
# For an explanation of handles, see the "Object Manager"
# (pp. 140-175) section of
#
# Windows Internals, Part 1: Covering Windows Server 2008 R2 and
# Windows 7 (6th ed.)
# Mark E. Russinovich, David A. Solomon, and Alex
# Ionescu. 2012. Microsoft Press.
if platformType == "win32":
_reservedFD = _NullFileDescriptorReservation()
else:
_reservedFD = _FileDescriptorReservation(lambda: open(os.devnull)) # type: ignore[assignment]
# Linux and other UNIX-like operating systems return EMFILE when a
# process has reached its soft limit of file descriptors. *BSD and
# Win32 raise (WSA)ENOBUFS when socket limits are reached. Linux can
# give ENFILE if the system is out of inodes, or ENOMEM if there is
# insufficient memory to allocate a new dentry. ECONNABORTED is
# documented as possible on all relevant platforms (Linux, Windows,
# macOS, and the BSDs) but occurs only on the BSDs. It occurs when a
# client sends a FIN or RST after the server sends a SYN|ACK but
# before application code calls accept(2). On Linux, calling
# accept(2) on such a listener returns a connection that fails as
# though the it were terminated after being fully established. This
# appears to be an implementation choice (see inet_accept in
# inet/ipv4/af_inet.c). On macOS, such a listener is not considered
# readable, so accept(2) will never be called. Calling accept(2) on
# such a listener, however, does not return at all.
_ACCEPT_ERRORS = (EMFILE, ENOBUFS, ENFILE, ENOMEM, ECONNABORTED)
@attr.s(auto_attribs=True)
class _BuffersLogs:
"""
A context manager that buffers any log events until after its
block exits.
@ivar _namespace: The namespace of the buffered events.
@type _namespace: L{str}.
@ivar _observer: The observer to which buffered log events will be
written
@type _observer: L{twisted.logger.ILogObserver}.
"""
_namespace: str
_observer: ILogObserver
_logs: List[LogEvent] = attr.ib(default=attr.Factory(list))
def __enter__(self):
"""
Enter a log buffering context.
@return: A logger that buffers log events.
@rtype: L{Logger}.
"""
return Logger(namespace=self._namespace, observer=self._logs.append)
def __exit__(self, excValue, excType, traceback):
"""
Exit a log buffering context and log all buffered events to
the provided observer.
@param excType: See L{object.__exit__}
@param excValue: See L{object.__exit__}
@param traceback: See L{object.__exit__}
"""
for event in self._logs:
self._observer(event)
def _accept(logger, accepts, listener, reservedFD):
"""
Return a generator that yields client sockets from the provided
listening socket until there are none left or an unrecoverable
error occurs.
@param logger: A logger to which C{accept}-related events will be
logged. This should not log to arbitrary observers that might
open a file descriptor to avoid claiming the C{EMFILE} file
descriptor on UNIX-like systems.
@type logger: L{Logger}
@param accepts: An iterable iterated over to limit the number
consecutive C{accept}s.
@type accepts: An iterable.
@param listener: The listening socket.
@type listener: L{socket.socket}
@param reservedFD: A reserved file descriptor that can be used to
recover from C{EMFILE} on UNIX-like systems.
@type reservedFD: L{_IFileDescriptorReservation}
@return: A generator that yields C{(socket, addr)} tuples from
L{socket.socket.accept}
"""
for _ in accepts:
try:
client, address = listener.accept()
except OSError as e:
if e.args[0] in (EWOULDBLOCK, EAGAIN):
# No more clients.
return
elif e.args[0] == EPERM:
# Netfilter on Linux may have rejected the
# connection, but we get told to try to accept()
# anyway.
continue
elif e.args[0] == EMFILE and reservedFD.available():
# Linux and other UNIX-like operating systems return
# EMFILE when a process has reached its soft limit of
# file descriptors. The reserved file descriptor is
# available, so it can be released to free up a
# descriptor for use by listener.accept()'s clients.
# Each client socket will be closed until the listener
# returns EAGAIN.
logger.info(
"EMFILE encountered;" " releasing reserved file descriptor."
)
# The following block should not run arbitrary code
# that might acquire its own file descriptor.
with reservedFD:
clientsToClose = _accept(logger, accepts, listener, reservedFD)
for clientToClose, closedAddress in clientsToClose:
clientToClose.close()
logger.info(
"EMFILE recovery:" " Closed socket from {address}",
address=closedAddress,
)
logger.info("Re-reserving EMFILE recovery file descriptor.")
return
elif e.args[0] in _ACCEPT_ERRORS:
logger.info(
"Could not accept new connection ({acceptError})",
acceptError=errorcode[e.args[0]],
)
return
else:
raise
else:
yield client, address
@implementer(IListeningPort)
class Port(base.BasePort, _SocketCloser):
"""
A TCP server port, listening for connections.
When a connection is accepted, this will call a factory's buildProtocol
with the incoming address as an argument, according to the specification
described in L{twisted.internet.interfaces.IProtocolFactory}.
If you wish to change the sort of transport that will be used, the
C{transport} attribute will be called with the signature expected for
C{Server.__init__}, so it can be replaced.
@ivar deferred: a deferred created when L{stopListening} is called, and
that will fire when connection is lost. This is not to be used it
directly: prefer the deferred returned by L{stopListening} instead.
@type deferred: L{defer.Deferred}
@ivar disconnecting: flag indicating that the L{stopListening} method has
been called and that no connections should be accepted anymore.
@type disconnecting: C{bool}
@ivar connected: flag set once the listen has successfully been called on
the socket.
@type connected: C{bool}
@ivar _type: A string describing the connections which will be created by
this port. Normally this is C{"TCP"}, since this is a TCP port, but
when the TLS implementation re-uses this class it overrides the value
with C{"TLS"}. Only used for logging.
@ivar _preexistingSocket: If not L{None}, a L{socket.socket} instance which
was created and initialized outside of the reactor and will be used to
listen for connections (instead of a new socket being created by this
L{Port}).
"""
socketType = socket.SOCK_STREAM
transport = Server
sessionno = 0
interface = ""
backlog = 50
_type = "TCP"
# Actual port number being listened on, only set to a non-None
# value when we are actually listening.
_realPortNumber: Optional[int] = None
# An externally initialized socket that we will use, rather than creating
# our own.
_preexistingSocket = None
addressFamily = socket.AF_INET
_addressType = address.IPv4Address
_logger = Logger()
def __init__(self, port, factory, backlog=50, interface="", reactor=None):
"""Initialize with a numeric port to listen on."""
base.BasePort.__init__(self, reactor=reactor)
self.port = port
self.factory = factory
self.backlog = backlog
if abstract.isIPv6Address(interface):
self.addressFamily = socket.AF_INET6
self._addressType = address.IPv6Address
self.interface = interface
@classmethod
def _fromListeningDescriptor(cls, reactor, fd, addressFamily, factory):
"""
Create a new L{Port} based on an existing listening I{SOCK_STREAM}
socket.
Arguments are the same as to L{Port.__init__}, except where noted.
@param fd: An integer file descriptor associated with a listening
socket. The socket must be in non-blocking mode. Any additional
attributes desired, such as I{FD_CLOEXEC}, must also be set already.
@param addressFamily: The address family (sometimes called I{domain}) of
the existing socket. For example, L{socket.AF_INET}.
@return: A new instance of C{cls} wrapping the socket given by C{fd}.
"""
port = socket.fromfd(fd, addressFamily, cls.socketType)
interface = _getsockname(port)[0]
self = cls(None, factory, None, interface, reactor)
self._preexistingSocket = port
return self
def __repr__(self) -> str:
if self._realPortNumber is not None:
return "<{} of {} on {}>".format(
self.__class__,
self.factory.__class__,
self._realPortNumber,
)
else:
return "<{} of {} (not listening)>".format(
self.__class__,
self.factory.__class__,
)
def createInternetSocket(self):
s = base.BasePort.createInternetSocket(self)
if platformType == "posix" and sys.platform != "cygwin":
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
return s
def startListening(self):
"""Create and bind my socket, and begin listening on it.
This is called on unserialization, and must be called after creating a
server to begin listening on the specified port.
"""
_reservedFD.reserve()
if self._preexistingSocket is None:
# Create a new socket and make it listen
try:
skt = self.createInternetSocket()
if self.addressFamily == socket.AF_INET6:
addr = _resolveIPv6(self.interface, self.port)
else:
addr = (self.interface, self.port)
skt.bind(addr)
except OSError as le:
raise CannotListenError(self.interface, self.port, le)
skt.listen(self.backlog)
else:
# Re-use the externally specified socket
skt = self._preexistingSocket
self._preexistingSocket = None
# Avoid shutting it down at the end.
self._shouldShutdown = False
# Make sure that if we listened on port 0, we update that to
# reflect what the OS actually assigned us.
self._realPortNumber = skt.getsockname()[1]
log.msg(
"%s starting on %s"
% (self._getLogPrefix(self.factory), self._realPortNumber)
)
# The order of the next 5 lines is kind of bizarre. If no one
# can explain it, perhaps we should re-arrange them.
self.factory.doStart()
self.connected = True
self.socket = skt
self.fileno = self.socket.fileno
self.numberAccepts = 100
self.startReading()
def _buildAddr(self, address):
return self._addressType("TCP", *address)
def doRead(self):
"""
Called when my socket is ready for reading.
This accepts a connection and calls self.protocol() to handle the
wire-level protocol.
"""
try:
if platformType == "posix":
numAccepts = self.numberAccepts
else:
# win32 event loop breaks if we do more than one accept()
# in an iteration of the event loop.
numAccepts = 1
with _BuffersLogs(
self._logger.namespace, self._logger.observer
) as bufferingLogger:
accepted = 0
clients = _accept(
bufferingLogger, range(numAccepts), self.socket, _reservedFD
)
for accepted, (skt, addr) in enumerate(clients, 1):
fdesc._setCloseOnExec(skt.fileno())
if len(addr) == 4:
# IPv6, make sure we get the scopeID if it
# exists
host = socket.getnameinfo(
addr, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
)
addr = tuple([host[0]] + list(addr[1:]))
protocol = self.factory.buildProtocol(self._buildAddr(addr))
if protocol is None:
skt.close()
continue
s = self.sessionno
self.sessionno = s + 1
transport = self.transport(
skt, protocol, addr, self, s, self.reactor
)
protocol.makeConnection(transport)
# Scale our synchronous accept loop according to traffic
# Reaching our limit on consecutive accept calls indicates
# there might be still more clients to serve the next time
# the reactor calls us. Prepare to accept some more.
if accepted == self.numberAccepts:
self.numberAccepts += 20
# Otherwise, don't attempt to accept any more clients than
# we just accepted or any less than 1.
else:
self.numberAccepts = max(1, accepted)
except BaseException:
# Note that in TLS mode, this will possibly catch SSL.Errors
# raised by self.socket.accept()
#
# There is no "except SSL.Error:" above because SSL may be
# None if there is no SSL support. In any case, all the
# "except SSL.Error:" suite would probably do is log.deferr()
# and return, so handling it here works just as well.
log.deferr()
def loseConnection(self, connDone=failure.Failure(main.CONNECTION_DONE)):
"""
Stop accepting connections on this port.
This will shut down the socket and call self.connectionLost(). It
returns a deferred which will fire successfully when the port is
actually closed, or with a failure if an error occurs shutting down.
"""
self.disconnecting = True
self.stopReading()
if self.connected:
self.deferred = deferLater(self.reactor, 0, self.connectionLost, connDone)
return self.deferred
stopListening = loseConnection
def _logConnectionLostMsg(self):
"""
Log message for closing port
"""
log.msg(f"({self._type} Port {self._realPortNumber} Closed)")
def connectionLost(self, reason):
"""
Cleans up the socket.
"""
self._logConnectionLostMsg()
self._realPortNumber = None
base.BasePort.connectionLost(self, reason)
self.connected = False
self._closeSocket(True)
del self.socket
del self.fileno
try:
self.factory.doStop()
finally:
self.disconnecting = False
def logPrefix(self):
"""Returns the name of my class, to prefix log entries with."""
return reflect.qual(self.factory.__class__)
def getHost(self):
"""
Return an L{IPv4Address} or L{IPv6Address} indicating the listening
address of this port.
"""
addr = _getsockname(self.socket)
return self._addressType("TCP", *addr)
class Connector(base.BaseConnector):
"""
A L{Connector} provides of L{twisted.internet.interfaces.IConnector} for
all POSIX-style reactors.
@ivar _addressType: the type returned by L{Connector.getDestination}.
Either L{IPv4Address} or L{IPv6Address}, depending on the type of
address.
@type _addressType: C{type}
"""
_addressType = address.IPv4Address
def __init__(self, host, port, factory, timeout, bindAddress, reactor=None):
if isinstance(port, str):
try:
port = socket.getservbyname(port, "tcp")
except OSError as e:
raise error.ServiceNameUnknownError(string=f"{e} ({port!r})")
self.host, self.port = host, port
if abstract.isIPv6Address(host):
self._addressType = address.IPv6Address
self.bindAddress = bindAddress
base.BaseConnector.__init__(self, factory, timeout, reactor)
def _makeTransport(self):
"""
Create a L{Client} bound to this L{Connector}.
@return: a new L{Client}
@rtype: L{Client}
"""
return Client(self.host, self.port, self.bindAddress, self, self.reactor)
def getDestination(self):
"""
@see: L{twisted.internet.interfaces.IConnector.getDestination}.
"""
return self._addressType("TCP", self.host, self.port)
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