Mostly implement hybrid TTY/socket mode for sudo and SSH.

Presently there is still no mechanism to add :attr:`tty_stream` to the
multiplexer after connection is successful, but for now it's not
expected that anything will be logged to it anyway.

Closes #148.

docs/internals.rst

@@ -402,27 +402,12 @@ Helper Functions
 
 .. currentmodule:: mitogen.master
 
-.. function:: create_child (\*args)
-
-    Create a child process whose stdin/stdout is connected to a socket,
-    returning `(pid, socket_obj)`.
+.. autofunction:: create_child
 
 
 .. currentmodule:: mitogen.master
 
-.. function:: tty_create_child (\*args)
-
-    Return a file descriptor connected to the master end of a pseudo-terminal,
-    whose slave end is connected to stdin/stdout/stderr of a new child process.
-    The child is created such that the pseudo-terminal becomes its controlling
-    TTY, ensuring access to /dev/tty returns a new file descriptor open on the
-    slave end.
-
-    :param list args:
-        :py:func:`os.execl` argument list.
-
-    :returns:
-        `(pid, fd)`
+.. autofunction:: tty_create_child
 
 
 .. currentmodule:: mitogen.master

mitogen/fork.py

@@ -108,7 +108,7 @@ class Stream(mitogen.parent.Stream):
             # Decouple the socket from the lifetime of the Python socket object.
             fd = os.dup(parentfp.fileno())
             parentfp.close()
-            return self.pid, fd
+            return self.pid, fd, None
         else:
             parentfp.close()
             self._wrap_child_main(childfp)
@@ -155,6 +155,6 @@ class Stream(mitogen.parent.Stream):
             # Don't trigger atexit handlers, they were copied from the parent.
             os._exit(0)
 
-    def _connect_bootstrap(self):
+    def _connect_bootstrap(self, extra_fd):
         # None required.
         pass

mitogen/parent.py

@@ -243,6 +243,12 @@ def create_socketpair():
 
 
 def create_child(*args):
+    """
+    Create a child process whose stdin/stdout is connected to a socket.
+
+    :returns:
+        `(pid, socket_obj, :data:`None`)`
+    """
     parentfp, childfp = create_socketpair()
     # When running under a monkey patches-enabled gevent, the socket module
     # yields file descriptors who already have O_NONBLOCK, which is
@@ -263,7 +269,7 @@ def create_child(*args):
 
     LOG.debug('create_child() child %d fd %d, parent %d, cmd: %s',
               proc.pid, fd, os.getpid(), Argv(args))
-    return proc.pid, fd
+    return proc.pid, fd, None
 
 
 def _acquire_controlling_tty():
@@ -271,13 +277,26 @@ def _acquire_controlling_tty():
     if sys.platform == 'linux2':
         # On Linux, the controlling tty becomes the first tty opened by a
         # process lacking any prior tty.
-        os.close(os.open(os.ttyname(0), os.O_RDWR))
+        os.close(os.open(os.ttyname(2), os.O_RDWR))
     if sys.platform.startswith('freebsd') or sys.platform == 'darwin':
         # On BSD an explicit ioctl is required.
-        fcntl.ioctl(0, termios.TIOCSCTTY)
+        fcntl.ioctl(2, termios.TIOCSCTTY)
 
 
 def tty_create_child(*args):
+    """
+    Return a file descriptor connected to the master end of a pseudo-terminal,
+    whose slave end is connected to stdin/stdout/stderr of a new child process.
+    The child is created such that the pseudo-terminal becomes its controlling
+    TTY, ensuring access to /dev/tty returns a new file descriptor open on the
+    slave end.
+
+    :param list args:
+        :py:func:`os.execl` argument list.
+
+    :returns:
+        `(pid, tty_fd, None)`
+    """
     master_fd, slave_fd = os.openpty()
     mitogen.core.set_block(slave_fd)
     disable_echo(master_fd)
@@ -295,7 +314,47 @@ def tty_create_child(*args):
     os.close(slave_fd)
     LOG.debug('tty_create_child() child %d fd %d, parent %d, cmd: %s',
               proc.pid, master_fd, os.getpid(), Argv(args))
-    return proc.pid, master_fd
+    return proc.pid, master_fd, None
+
+
+def hybrid_tty_create_child(*args):
+    """
+    Like :func:`tty_create_child`, except attach stdin/stdout to a socketpair
+    like :func:`create_child`, but leave stderr and the controlling TTY
+    attached to a TTY.
+
+    :param list args:
+        :py:func:`os.execl` argument list.
+
+    :returns:
+        `(pid, socketpair_fd, tty_fd)`
+    """
+    master_fd, slave_fd = os.openpty()
+    parentfp, childfp = create_socketpair()
+
+    mitogen.core.set_block(slave_fd)
+    mitogen.core.set_block(childfp)
+    disable_echo(master_fd)
+    disable_echo(slave_fd)
+
+    proc = subprocess.Popen(
+        args=args,
+        stdin=childfp,
+        stdout=childfp,
+        stderr=slave_fd,
+        preexec_fn=_acquire_controlling_tty,
+        close_fds=True,
+    )
+
+    os.close(slave_fd)
+    childfp.close()
+    # Decouple the socket from the lifetime of the Python socket object.
+    stdio_fd = os.dup(parentfp.fileno())
+    parentfp.close()
+
+    LOG.debug('hybrid_tty_create_child() pid=%d stdio=%d, tty=%d, cmd: %s',
+              proc.pid, stdio_fd, master_fd, Argv(args))
+    return proc.pid, stdio_fd, master_fd
 
 
 def write_all(fd, s, deadline=None):
@@ -319,7 +378,7 @@ def write_all(fd, s, deadline=None):
         written += n
 
 
-def iter_read(fd, deadline=None):
+def iter_read(fds, deadline=None):
     bits = []
     timeout = None
 
@@ -329,26 +388,27 @@ def iter_read(fd, deadline=None):
             if timeout == 0:
                 break
 
-        rfds, _, _ = select.select([fd], [], [], timeout)
+        rfds, _, _ = select.select(fds, [], [], timeout)
         if not rfds:
             continue
 
-        s, disconnected = mitogen.core.io_op(os.read, fd, 4096)
-        IOLOG.debug('iter_read(%r) -> %r', fd, s)
-        if disconnected or not s:
-            raise mitogen.core.StreamError(
-                'EOF on stream; last 300 bytes received: %r' %
-                (''.join(bits)[-300:],)
-            )
+        for fd in rfds:
+            s, disconnected = mitogen.core.io_op(os.read, fd, 4096)
+            IOLOG.debug('iter_read(%r) -> %r', fd, s)
+            if disconnected or not s:
+                raise mitogen.core.StreamError(
+                    'EOF on stream; last 300 bytes received: %r' %
+                    (''.join(bits)[-300:],)
+                )
 
-        bits.append(s)
-        yield s
+            bits.append(s)
+            yield s
 
     raise mitogen.core.TimeoutError('read timed out')
 
 
 def discard_until(fd, s, deadline):
-    for buf in iter_read(fd, deadline):
+    for buf in iter_read([fd], deadline):
         if IOLOG.level == logging.DEBUG:
             for line in buf.splitlines():
                 IOLOG.debug('discard_until: discarding %r', line)
@@ -414,6 +474,36 @@ def _proxy_connect(name, method_name, kwargs, econtext):
     }
 
 
+class TtyLogStream(mitogen.core.BasicStream):
+    """
+    For "hybrid TTY/socketpair" mode, after a connection has been setup, a
+    spare TTY file descriptor will exist that cannot be closed, and to which
+    SSH or sudo may continue writing log messages.
+
+    The descriptor cannot be closed since the UNIX TTY layer will send a
+    termination signal to any processes whose controlling TTY is the TTY that
+    has been closed.
+
+    TtyLogStream takes over this descriptor and creates corresponding log
+    messages for anything written to it.
+    """
+
+    def __init__(self, tty_fd, stream):
+        self.receive_side = mitogen.core.Side(stream, tty_fd)
+        self.transmit_side = self.receive_side
+        self.stream = stream
+
+    def __repr__(self):
+        return 'mitogen.parent.TtyLogStream(%r)' % (self.stream,)
+
+    def on_receive(self, broker):
+        buf = self.receive_side.read()
+        if not buf:
+            return self.on_disconnect(broker)
+
+        LOG.debug('%r.on_receive(): %r', self, buf)
+
+
 class Stream(mitogen.core.Stream):
     """
     Base for streams capable of starting new slaves.
@@ -597,21 +687,21 @@ class Stream(mitogen.core.Stream):
 
     def connect(self):
         LOG.debug('%r.connect()', self)
-        self.pid, fd = self.start_child()
+        self.pid, fd, extra_fd = self.start_child()
         self.name = '%s.%s' % (self.name_prefix, self.pid)
         self.receive_side = mitogen.core.Side(self, fd)
         self.transmit_side = mitogen.core.Side(self, os.dup(fd))
         LOG.debug('%r.connect(): child process stdin/stdout=%r',
                   self, self.receive_side.fd)
 
-        self._connect_bootstrap()
+        self._connect_bootstrap(extra_fd)
 
     def _ec0_received(self):
         LOG.debug('%r._ec0_received()', self)
         write_all(self.transmit_side.fd, self.get_preamble())
         discard_until(self.receive_side.fd, 'EC1\n', time.time() + 10.0)
 
-    def _connect_bootstrap(self):
+    def _connect_bootstrap(self, extra_fd):
         deadline = time.time() + self.connect_timeout
         discard_until(self.receive_side.fd, 'EC0\n', deadline)
         self._ec0_received()

mitogen/ssh.py

@@ -52,9 +52,13 @@ class PasswordError(mitogen.core.StreamError):
 
 
 class Stream(mitogen.parent.Stream):
-    create_child = staticmethod(mitogen.parent.tty_create_child)
+    create_child = staticmethod(mitogen.parent.hybrid_tty_create_child)
     python_path = 'python2.7'
 
+    #: Once connected, points to the corresponding TtyLogStream, allowing it to
+    #: be disconnected at the same time this stream is being torn down.
+    tty_stream = None
+
     #: The path to the SSH binary.
     ssh_path = 'ssh'
 
@@ -83,6 +87,10 @@ class Stream(mitogen.parent.Stream):
         if ssh_args:
             self.ssh_args = ssh_args
 
+    def on_disconnect(self, broker):
+        self.tty_stream.on_disconnect(broker)
+        super(Stream, self).on_disconnect(broker)
+
     def get_boot_command(self):
         bits = [self.ssh_path]
         # bits += ['-o', 'BatchMode yes']
@@ -124,10 +132,12 @@ class Stream(mitogen.parent.Stream):
     password_incorrect_msg = 'SSH password is incorrect'
     password_required_msg = 'SSH password was requested, but none specified'
 
-    def _connect_bootstrap(self):
+    def _connect_bootstrap(self, extra_fd):
+        self.tty_stream = mitogen.parent.TtyLogStream(extra_fd, self)
+
         password_sent = False
         it = mitogen.parent.iter_read(
-            fd=self.receive_side.fd,
+            fds=[self.receive_side.fd, extra_fd],
             deadline=self.connect_deadline
         )
 
@@ -145,6 +155,7 @@ class Stream(mitogen.parent.Stream):
                 if self.password is None:
                     raise PasswordError(self.password_required_msg)
                 LOG.debug('sending password')
-                self.transmit_side.write(self.password + '\n')
+                self.tty_stream.transmit_side.write(self.password + '\n')
                 password_sent = True
+
         raise mitogen.core.StreamError('bootstrap failed')

mitogen/sudo.py

@@ -103,7 +103,12 @@ class PasswordError(mitogen.core.StreamError):
 
 
 class Stream(mitogen.parent.Stream):
-    create_child = staticmethod(mitogen.parent.tty_create_child)
+    create_child = staticmethod(mitogen.parent.hybrid_tty_create_child)
+
+    #: Once connected, points to the corresponding TtyLogStream, allowing it to
+    #: be disconnected at the same time this stream is being torn down.
+    tty_stream = None
+
     sudo_path = 'sudo'
     username = 'root'
     password = None
@@ -131,6 +136,10 @@ class Stream(mitogen.parent.Stream):
         super(Stream, self).connect()
         self.name = 'sudo.' + self.username
 
+    def on_disconnect(self, broker):
+        self.tty_stream.on_disconnect(broker)
+        super(Stream, self).on_disconnect(broker)
+
     def get_boot_command(self):
         # Note: sudo did not introduce long-format option processing until July
         # 2013, so even though we parse long-format options, we always supply
@@ -147,10 +156,12 @@ class Stream(mitogen.parent.Stream):
     password_incorrect_msg = 'sudo password is incorrect'
     password_required_msg = 'sudo password is required'
 
-    def _connect_bootstrap(self):
+    def _connect_bootstrap(self, extra_fd):
+        self.tty_stream = mitogen.parent.TtyLogStream(extra_fd, self)
+
         password_sent = False
         it = mitogen.parent.iter_read(
-            fd=self.receive_side.fd,
+            fds=[self.receive_side.fd, extra_fd],
             deadline=self.connect_deadline,
         )
 
@@ -165,6 +176,6 @@ class Stream(mitogen.parent.Stream):
                 if password_sent:
                     raise PasswordError(self.password_incorrect_msg)
                 LOG.debug('sending password')
-                os.write(self.transmit_side.fd, self.password + '\n')
+                self.tty_stream.transmit_side.write(self.password + '\n')
                 password_sent = True
         raise mitogen.core.StreamError('bootstrap failed')

tests/parent_test.py

@@ -13,7 +13,7 @@ class StreamErrorTest(testlib.RouterMixin, testlib.TestCase):
     def test_direct_eof(self):
         e = self.assertRaises(mitogen.core.StreamError,
             lambda: self.router.local(
-                python_path='/bin/true',
+                python_path='true',
                 connect_timeout=3,
             )
         )
@@ -25,7 +25,7 @@ class StreamErrorTest(testlib.RouterMixin, testlib.TestCase):
         e = self.assertRaises(mitogen.core.StreamError,
             lambda: self.router.local(
                 via=local,
-                python_path='/bin/true',
+                python_path='true',
                 connect_timeout=3,
             )
         )
@@ -77,11 +77,11 @@ class TtyCreateChildTest(unittest2.TestCase):
         # read a password.
         tf = tempfile.NamedTemporaryFile()
         try:
-            pid, fd = self.func(
+            pid, fd, _ = self.func(
                 'bash', '-c', 'exec 2>%s; echo hi > /dev/tty' % (tf.name,)
             )
             deadline = time.time() + 5.0
-            for line in mitogen.parent.iter_read(fd, deadline):
+            for line in mitogen.parent.iter_read([fd], deadline):
                 self.assertEquals('hi\n', line)
                 break
             waited_pid, status = os.waitpid(pid, 0)
@@ -104,7 +104,7 @@ class IterReadTest(unittest2.TestCase):
     def test_no_deadline(self):
         proc = self.make_proc()
         try:
-            reader = self.func(proc.stdout.fileno())
+            reader = self.func([proc.stdout.fileno()])
             for i, chunk in enumerate(reader, 1):
                 self.assertEqual(i, int(chunk))
                 if i > 3:
@@ -114,7 +114,7 @@ class IterReadTest(unittest2.TestCase):
 
     def test_deadline_exceeded_before_call(self):
         proc = self.make_proc()
-        reader = self.func(proc.stdout.fileno(), 0)
+        reader = self.func([proc.stdout.fileno()], 0)
         try:
             got = []
             try:
@@ -128,7 +128,7 @@ class IterReadTest(unittest2.TestCase):
 
     def test_deadline_exceeded_during_call(self):
         proc = self.make_proc()
-        reader = self.func(proc.stdout.fileno(), time.time() + 0.4)
+        reader = self.func([proc.stdout.fileno()], time.time() + 0.4)
         try:
             got = []
             try: