Implement initial Python bindings for Open vSwitch database.

[sliver-openvswitch.git] / python / ovs / socket_util.py

diff --git a/python/ovs/socket_util.py b/python/ovs/socket_util.py
new file mode 100644 (file)
index 0000000..4f4f603
--- /dev/null
+++ b/python/ovs/socket_util.py
@@ -0,0 +1,143 @@
+# Copyright (c) 2010 Nicira Networks
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import errno
+import logging
+import os
+import select
+import socket
+import sys
+
+import ovs.fatal_signal
+
+def make_unix_socket(style, nonblock, bind_path, connect_path):
+    """Creates a Unix domain socket in the given 'style' (either
+    socket.SOCK_DGRAM or socket.SOCK_STREAM) that is bound to 'bind_path' (if
+    'bind_path' is not None) and connected to 'connect_path' (if 'connect_path'
+    is not None).  If 'nonblock' is true, the socket is made non-blocking.
+
+    Returns (error, socket): on success 'error' is 0 and 'socket' is a new
+    socket object, on failure 'error' is a positive errno value and 'socket' is
+    None."""
+
+    try:
+        sock = socket.socket(socket.AF_UNIX, style)
+    except socket.error, e:
+        return get_exception_errno(e), None
+
+    try:
+        if nonblock:
+            set_nonblocking(sock)
+        if bind_path is not None:
+            # Delete bind_path but ignore ENOENT.
+            try:
+                os.unlink(bind_path)
+            except OSError, e:
+                if e.errno != errno.ENOENT:
+                    return e.errno, None
+
+            ovs.fatal_signal.add_file_to_unlink(bind_path)
+            sock.bind(bind_path)
+
+            try:
+                if sys.hexversion >= 0x02060000:
+                    os.fchmod(sock.fileno(), 0700)
+                else:
+                    os.chmod("/dev/fd/%d" % sock.fileno(), 0700)
+            except OSError, e:
+                pass
+        if connect_path is not None:
+            try:
+                sock.connect(connect_path)
+            except socket.error, e:
+                if get_exception_errno(e) != errno.EINPROGRESS:
+                    raise
+        return 0, sock
+    except socket.error, e:
+        sock.close()
+        try:
+            os.unlink(bind_path)
+        except OSError, e:
+            pass
+        if bind_path is not None:
+            ovs.fatal_signal.add_file_to_unlink(bind_path)
+        return get_exception_errno(e), None
+
+def check_connection_completion(sock):
+    p = select.poll()
+    p.register(sock, select.POLLOUT)
+    if len(p.poll(0)) == 1:
+        return get_socket_error(sock)
+    else:
+        return errno.EAGAIN
+
+def get_socket_error(sock):
+    """Returns the errno value associated with 'socket' (0 if no error) and
+    resets the socket's error status."""
+    return sock.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
+
+def get_exception_errno(e):
+    """A lot of methods on Python socket objects raise socket.error, but that
+    exception is documented as having two completely different forms of
+    arguments: either a string or a (errno, string) tuple.  We only want the
+    errno."""
+    if type(e.args) == tuple:
+        return e.args[0]
+    else:
+        return errno.EPROTO
+
+null_fd = -1
+def get_null_fd():
+    """Returns a readable and writable fd for /dev/null, if successful,
+    otherwise a negative errno value.  The caller must not close the returned
+    fd (because the same fd will be handed out to subsequent callers)."""
+    global null_fd
+    if null_fd < 0:
+        try:
+            null_fd = os.open("/dev/null", os.O_RDWR)
+        except OSError, e:
+            logging.error("could not open /dev/null: %s"
+                          % os.strerror(e.errno))
+            return -e.errno
+    return null_fd
+
+def write_fully(fd, buf):
+    """Returns an (error, bytes_written) tuple where 'error' is 0 on success,
+    otherwise a positive errno value, and 'bytes_written' is the number of
+    bytes that were written before the error occurred.  'error' is 0 if and
+    only if 'bytes_written' is len(buf)."""
+    bytes_written = 0
+    if len(buf) == 0:
+        return 0, 0
+    while True:
+        try:
+            retval = os.write(fd, buf)
+            assert retval >= 0
+            if retval == len(buf):
+                return 0, bytes_written + len(buf)
+            elif retval == 0:
+                logging.warning("write returned 0")
+                return errno.EPROTO, bytes_written
+            else:
+                bytes_written += retval
+                buf = buf[:retval]
+        except OSError, e:
+            return e.errno, bytes_written
+
+def set_nonblocking(sock):
+    try:
+        sock.setblocking(0)
+    except socket.error, e:
+        logging.error("could not set nonblocking mode on socket: %s"
+                      % os.strerror(get_socket_error(e)))