path: root/contrib/python/Twisted/py3/twisted/internet/posixbase.py

# -*- test-case-name: twisted.test.test_internet,twisted.internet.test.test_posixbase -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Posix reactor base class
"""


import socket
import sys
from typing import Sequence

from zope.interface import classImplements, implementer

from twisted.internet import error, tcp, udp
from twisted.internet.base import ReactorBase
from twisted.internet.interfaces import (
    IHalfCloseableDescriptor,
    IReactorFDSet,
    IReactorMulticast,
    IReactorProcess,
    IReactorSocket,
    IReactorSSL,
    IReactorTCP,
    IReactorUDP,
    IReactorUNIX,
    IReactorUNIXDatagram,
)
from twisted.internet.main import CONNECTION_DONE, CONNECTION_LOST
from twisted.python import failure, log
from twisted.python.runtime import platform, platformType
from ._signals import (
    SignalHandling,
    _ChildSignalHandling,
    _IWaker,
    _MultiSignalHandling,
    _Waker,
)

# Exceptions that doSelect might return frequently
_NO_FILENO = error.ConnectionFdescWentAway("Handler has no fileno method")
_NO_FILEDESC = error.ConnectionFdescWentAway("File descriptor lost")


try:
    from twisted.protocols import tls as _tls
except ImportError:
    tls = None
else:
    tls = _tls

try:
    from twisted.internet import ssl as _ssl
except ImportError:
    ssl = None
else:
    ssl = _ssl

unixEnabled = platformType == "posix"

processEnabled = False
if unixEnabled:
    from twisted.internet import process, unix

    processEnabled = True


if platform.isWindows():
    try:
        import win32process  # type: ignore[import]

        processEnabled = True
    except ImportError:
        win32process = None


class _DisconnectSelectableMixin:
    """
    Mixin providing the C{_disconnectSelectable} method.
    """

    def _disconnectSelectable(
        self,
        selectable,
        why,
        isRead,
        faildict={
            error.ConnectionDone: failure.Failure(error.ConnectionDone()),
            error.ConnectionLost: failure.Failure(error.ConnectionLost()),
        },
    ):
        """
        Utility function for disconnecting a selectable.

        Supports half-close notification, isRead should be boolean indicating
        whether error resulted from doRead().
        """
        self.removeReader(selectable)
        f = faildict.get(why.__class__)
        if f:
            if (
                isRead
                and why.__class__ == error.ConnectionDone
                and IHalfCloseableDescriptor.providedBy(selectable)
            ):
                selectable.readConnectionLost(f)
            else:
                self.removeWriter(selectable)
                selectable.connectionLost(f)
        else:
            self.removeWriter(selectable)
            selectable.connectionLost(failure.Failure(why))


@implementer(IReactorTCP, IReactorUDP, IReactorMulticast)
class PosixReactorBase(_DisconnectSelectableMixin, ReactorBase):
    """
    A basis for reactors that use file descriptors.

    @ivar _childWaker: L{None} or a reference to the L{_SIGCHLDWaker}
        which is used to properly notice child process termination.
    """

    _childWaker = None

    # Callable that creates a waker, overrideable so that subclasses can
    # substitute their own implementation:
    def _wakerFactory(self) -> _IWaker:
        return _Waker()

    def installWaker(self):
        """
        Install a `waker' to allow threads and signals to wake up the IO thread.

        We use the self-pipe trick (http://cr.yp.to/docs/selfpipe.html) to wake
        the reactor. On Windows we use a pair of sockets.
        """
        if not self.waker:
            self.waker = self._wakerFactory()
            self._internalReaders.add(self.waker)
            self.addReader(self.waker)

    def _signalsFactory(self) -> SignalHandling:
        """
        Customize reactor signal handling to support child processes on POSIX
        platforms.
        """
        baseHandling = super()._signalsFactory()
        # If we're on a platform that uses signals for process event signaling
        if platformType == "posix":
            # Compose ...
            return _MultiSignalHandling(
                (
                    # the base signal handling behavior ...
                    baseHandling,
                    # with our extra SIGCHLD handling behavior.
                    _ChildSignalHandling(
                        self._addInternalReader,
                        self._removeInternalReader,
                    ),
                )
            )

        # Otherwise just use the base behavior
        return baseHandling

    # IReactorProcess

    def spawnProcess(
        self,
        processProtocol,
        executable,
        args=(),
        env={},
        path=None,
        uid=None,
        gid=None,
        usePTY=0,
        childFDs=None,
    ):
        if platformType == "posix":
            if usePTY:
                if childFDs is not None:
                    raise ValueError(
                        "Using childFDs is not supported with usePTY=True."
                    )
                return process.PTYProcess(
                    self, executable, args, env, path, processProtocol, uid, gid, usePTY
                )
            else:
                return process.Process(
                    self,
                    executable,
                    args,
                    env,
                    path,
                    processProtocol,
                    uid,
                    gid,
                    childFDs,
                )
        elif platformType == "win32":
            if uid is not None:
                raise ValueError("Setting UID is unsupported on this platform.")
            if gid is not None:
                raise ValueError("Setting GID is unsupported on this platform.")
            if usePTY:
                raise ValueError("The usePTY parameter is not supported on Windows.")
            if childFDs:
                raise ValueError("Customizing childFDs is not supported on Windows.")

            if win32process:
                from twisted.internet._dumbwin32proc import Process

                return Process(self, processProtocol, executable, args, env, path)
            else:
                raise NotImplementedError(
                    "spawnProcess not available since pywin32 is not installed."
                )
        else:
            raise NotImplementedError(
                "spawnProcess only available on Windows or POSIX."
            )

    # IReactorUDP

    def listenUDP(self, port, protocol, interface="", maxPacketSize=8192):
        """Connects a given L{DatagramProtocol} to the given numeric UDP port.

        @returns: object conforming to L{IListeningPort}.
        """
        p = udp.Port(port, protocol, interface, maxPacketSize, self)
        p.startListening()
        return p

    # IReactorMulticast

    def listenMulticast(
        self, port, protocol, interface="", maxPacketSize=8192, listenMultiple=False
    ):
        """Connects a given DatagramProtocol to the given numeric UDP port.

        EXPERIMENTAL.

        @returns: object conforming to IListeningPort.
        """
        p = udp.MulticastPort(
            port, protocol, interface, maxPacketSize, self, listenMultiple
        )
        p.startListening()
        return p

    # IReactorUNIX

    def connectUNIX(self, address, factory, timeout=30, checkPID=0):
        assert unixEnabled, "UNIX support is not present"
        c = unix.Connector(address, factory, timeout, self, checkPID)
        c.connect()
        return c

    def listenUNIX(self, address, factory, backlog=50, mode=0o666, wantPID=0):
        assert unixEnabled, "UNIX support is not present"
        p = unix.Port(address, factory, backlog, mode, self, wantPID)
        p.startListening()
        return p

    # IReactorUNIXDatagram

    def listenUNIXDatagram(self, address, protocol, maxPacketSize=8192, mode=0o666):
        """
        Connects a given L{DatagramProtocol} to the given path.

        EXPERIMENTAL.

        @returns: object conforming to L{IListeningPort}.
        """
        assert unixEnabled, "UNIX support is not present"
        p = unix.DatagramPort(address, protocol, maxPacketSize, mode, self)
        p.startListening()
        return p

    def connectUNIXDatagram(
        self, address, protocol, maxPacketSize=8192, mode=0o666, bindAddress=None
    ):
        """
        Connects a L{ConnectedDatagramProtocol} instance to a path.

        EXPERIMENTAL.
        """
        assert unixEnabled, "UNIX support is not present"
        p = unix.ConnectedDatagramPort(
            address, protocol, maxPacketSize, mode, bindAddress, self
        )
        p.startListening()
        return p

    # IReactorSocket (no AF_UNIX on Windows)

    if unixEnabled:
        _supportedAddressFamilies: Sequence[socket.AddressFamily] = (
            socket.AF_INET,
            socket.AF_INET6,
            socket.AF_UNIX,
        )
    else:
        _supportedAddressFamilies = (
            socket.AF_INET,
            socket.AF_INET6,
        )

    def adoptStreamPort(self, fileDescriptor, addressFamily, factory):
        """
        Create a new L{IListeningPort} from an already-initialized socket.

        This just dispatches to a suitable port implementation (eg from
        L{IReactorTCP}, etc) based on the specified C{addressFamily}.

        @see: L{twisted.internet.interfaces.IReactorSocket.adoptStreamPort}
        """
        if addressFamily not in self._supportedAddressFamilies:
            raise error.UnsupportedAddressFamily(addressFamily)

        if unixEnabled and addressFamily == socket.AF_UNIX:
            p = unix.Port._fromListeningDescriptor(self, fileDescriptor, factory)
        else:
            p = tcp.Port._fromListeningDescriptor(
                self, fileDescriptor, addressFamily, factory
            )
        p.startListening()
        return p

    def adoptStreamConnection(self, fileDescriptor, addressFamily, factory):
        """
        @see:
            L{twisted.internet.interfaces.IReactorSocket.adoptStreamConnection}
        """
        if addressFamily not in self._supportedAddressFamilies:
            raise error.UnsupportedAddressFamily(addressFamily)

        if unixEnabled and addressFamily == socket.AF_UNIX:
            return unix.Server._fromConnectedSocket(fileDescriptor, factory, self)
        else:
            return tcp.Server._fromConnectedSocket(
                fileDescriptor, addressFamily, factory, self
            )

    def adoptDatagramPort(
        self, fileDescriptor, addressFamily, protocol, maxPacketSize=8192
    ):
        if addressFamily not in (socket.AF_INET, socket.AF_INET6):
            raise error.UnsupportedAddressFamily(addressFamily)

        p = udp.Port._fromListeningDescriptor(
            self, fileDescriptor, addressFamily, protocol, maxPacketSize=maxPacketSize
        )
        p.startListening()
        return p

    # IReactorTCP

    def listenTCP(self, port, factory, backlog=50, interface=""):
        p = tcp.Port(port, factory, backlog, interface, self)
        p.startListening()
        return p

    def connectTCP(self, host, port, factory, timeout=30, bindAddress=None):
        c = tcp.Connector(host, port, factory, timeout, bindAddress, self)
        c.connect()
        return c

    # IReactorSSL (sometimes, not implemented)

    def connectSSL(
        self, host, port, factory, contextFactory, timeout=30, bindAddress=None
    ):
        if tls is not None:
            tlsFactory = tls.TLSMemoryBIOFactory(contextFactory, True, factory)
            return self.connectTCP(host, port, tlsFactory, timeout, bindAddress)
        elif ssl is not None:
            c = ssl.Connector(
                host, port, factory, contextFactory, timeout, bindAddress, self
            )
            c.connect()
            return c
        else:
            assert False, "SSL support is not present"

    def listenSSL(self, port, factory, contextFactory, backlog=50, interface=""):
        if tls is not None:
            tlsFactory = tls.TLSMemoryBIOFactory(contextFactory, False, factory)
            port = self.listenTCP(port, tlsFactory, backlog, interface)
            port._type = "TLS"
            return port
        elif ssl is not None:
            p = ssl.Port(port, factory, contextFactory, backlog, interface, self)
            p.startListening()
            return p
        else:
            assert False, "SSL support is not present"

    def _removeAll(self, readers, writers):
        """
        Remove all readers and writers, and list of removed L{IReadDescriptor}s
        and L{IWriteDescriptor}s.

        Meant for calling from subclasses, to implement removeAll, like::

          def removeAll(self):
              return self._removeAll(self._reads, self._writes)

        where C{self._reads} and C{self._writes} are iterables.
        """
        removedReaders = set(readers) - self._internalReaders
        for reader in removedReaders:
            self.removeReader(reader)

        removedWriters = set(writers)
        for writer in removedWriters:
            self.removeWriter(writer)

        return list(removedReaders | removedWriters)


class _PollLikeMixin:
    """
    Mixin for poll-like reactors.

    Subclasses must define the following attributes::

      - _POLL_DISCONNECTED - Bitmask for events indicating a connection was
        lost.
      - _POLL_IN - Bitmask for events indicating there is input to read.
      - _POLL_OUT - Bitmask for events indicating output can be written.

    Must be mixed in to a subclass of PosixReactorBase (for
    _disconnectSelectable).
    """

    def _doReadOrWrite(self, selectable, fd, event):
        """
        fd is available for read or write, do the work and raise errors if
        necessary.
        """
        why = None
        inRead = False
        if event & self._POLL_DISCONNECTED and not (event & self._POLL_IN):
            # Handle disconnection.  But only if we finished processing all
            # the pending input.
            if fd in self._reads:
                # If we were reading from the descriptor then this is a
                # clean shutdown.  We know there are no read events pending
                # because we just checked above.  It also might be a
                # half-close (which is why we have to keep track of inRead).
                inRead = True
                why = CONNECTION_DONE
            else:
                # If we weren't reading, this is an error shutdown of some
                # sort.
                why = CONNECTION_LOST
        else:
            # Any non-disconnect event turns into a doRead or a doWrite.
            try:
                # First check to see if the descriptor is still valid.  This
                # gives fileno() a chance to raise an exception, too.
                # Ideally, disconnection would always be indicated by the
                # return value of doRead or doWrite (or an exception from
                # one of those methods), but calling fileno here helps make
                # buggy applications more transparent.
                if selectable.fileno() == -1:
                    # -1 is sort of a historical Python artifact.  Python
                    # files and sockets used to change their file descriptor
                    # to -1 when they closed.  For the time being, we'll
                    # continue to support this anyway in case applications
                    # replicated it, plus abstract.FileDescriptor.fileno
                    # returns -1.  Eventually it'd be good to deprecate this
                    # case.
                    why = _NO_FILEDESC
                else:
                    if event & self._POLL_IN:
                        # Handle a read event.
                        why = selectable.doRead()
                        inRead = True
                    if not why and event & self._POLL_OUT:
                        # Handle a write event, as long as doRead didn't
                        # disconnect us.
                        why = selectable.doWrite()
                        inRead = False
            except BaseException:
                # Any exception from application code gets logged and will
                # cause us to disconnect the selectable.
                why = sys.exc_info()[1]
                log.err()
        if why:
            self._disconnectSelectable(selectable, why, inRead)


@implementer(IReactorFDSet)
class _ContinuousPolling(_PollLikeMixin, _DisconnectSelectableMixin):
    """
    Schedule reads and writes based on the passage of time, rather than
    notification.

    This is useful for supporting polling filesystem files, which C{epoll(7)}
    does not support.

    The implementation uses L{_PollLikeMixin}, which is a bit hacky, but
    re-implementing and testing the relevant code yet again is unappealing.

    @ivar _reactor: The L{EPollReactor} that is using this instance.

    @ivar _loop: A C{LoopingCall} that drives the polling, or L{None}.

    @ivar _readers: A C{set} of C{FileDescriptor} objects that should be read
        from.

    @ivar _writers: A C{set} of C{FileDescriptor} objects that should be
        written to.
    """

    # Attributes for _PollLikeMixin
    _POLL_DISCONNECTED = 1
    _POLL_IN = 2
    _POLL_OUT = 4

    def __init__(self, reactor):
        self._reactor = reactor
        self._loop = None
        self._readers = set()
        self._writers = set()

    def _checkLoop(self):
        """
        Start or stop a C{LoopingCall} based on whether there are readers and
        writers.
        """
        if self._readers or self._writers:
            if self._loop is None:
                from twisted.internet.task import _EPSILON, LoopingCall

                self._loop = LoopingCall(self.iterate)
                self._loop.clock = self._reactor
                # LoopingCall seems unhappy with timeout of 0, so use very
                # small number:
                self._loop.start(_EPSILON, now=False)
        elif self._loop:
            self._loop.stop()
            self._loop = None

    def iterate(self):
        """
        Call C{doRead} and C{doWrite} on all readers and writers respectively.
        """
        for reader in list(self._readers):
            self._doReadOrWrite(reader, reader, self._POLL_IN)
        for writer in list(self._writers):
            self._doReadOrWrite(writer, writer, self._POLL_OUT)

    def addReader(self, reader):
        """
        Add a C{FileDescriptor} for notification of data available to read.
        """
        self._readers.add(reader)
        self._checkLoop()

    def addWriter(self, writer):
        """
        Add a C{FileDescriptor} for notification of data available to write.
        """
        self._writers.add(writer)
        self._checkLoop()

    def removeReader(self, reader):
        """
        Remove a C{FileDescriptor} from notification of data available to read.
        """
        try:
            self._readers.remove(reader)
        except KeyError:
            return
        self._checkLoop()

    def removeWriter(self, writer):
        """
        Remove a C{FileDescriptor} from notification of data available to
        write.
        """
        try:
            self._writers.remove(writer)
        except KeyError:
            return
        self._checkLoop()

    def removeAll(self):
        """
        Remove all readers and writers.
        """
        result = list(self._readers | self._writers)
        # Don't reset to new value, since self.isWriting and .isReading refer
        # to the existing instance:
        self._readers.clear()
        self._writers.clear()
        return result

    def getReaders(self):
        """
        Return a list of the readers.
        """
        return list(self._readers)

    def getWriters(self):
        """
        Return a list of the writers.
        """
        return list(self._writers)

    def isReading(self, fd):
        """
        Checks if the file descriptor is currently being observed for read
        readiness.

        @param fd: The file descriptor being checked.
        @type fd: L{twisted.internet.abstract.FileDescriptor}
        @return: C{True} if the file descriptor is being observed for read
            readiness, C{False} otherwise.
        @rtype: C{bool}
        """
        return fd in self._readers

    def isWriting(self, fd):
        """
        Checks if the file descriptor is currently being observed for write
        readiness.

        @param fd: The file descriptor being checked.
        @type fd: L{twisted.internet.abstract.FileDescriptor}
        @return: C{True} if the file descriptor is being observed for write
            readiness, C{False} otherwise.
        @rtype: C{bool}
        """
        return fd in self._writers


if tls is not None or ssl is not None:
    classImplements(PosixReactorBase, IReactorSSL)
if unixEnabled:
    classImplements(PosixReactorBase, IReactorUNIX, IReactorUNIXDatagram)
if processEnabled:
    classImplements(PosixReactorBase, IReactorProcess)
if getattr(socket, "fromfd", None) is not None:
    classImplements(PosixReactorBase, IReactorSocket)

__all__ = ["PosixReactorBase"]