Tests and documentation for systemd integration

Some tests and documentation for the systemd notification feature.
Also fixes some corner case issues detected while writing the tests.

docs/requirements.rst

@@ -49,6 +49,8 @@ Supports:
 
 * IPv4 TCP
 * IPv4 DNS
+* IPv6 TCP
+* IPv6 DNS
 
 Requires:
 
@@ -72,3 +74,19 @@ Additional Suggested Software
 
 - You may want to use autossh, available in various package management
   systems
+- If you are using systemd, sshuttle can notify it when the connection to
+  the remote end is established and the firewall rules are installed
+
+.. code-block:: ini
+   :emphasize-lines: 6
+
+   [Unit]
+   Description=sshuttle
+   After=network.target
+   
+   [Service]
+   Type=notify
+   ExecStart=/usr/bin/sshuttle --dns --remote <user>@<server> <subnets...>
+   
+   [Install]
+   WantedBy=multi-user.target

sshuttle/sdnotify.py

 import socket
 import os
-from sshuttle.helpers import debug1, debug2, debug3
+from sshuttle.helpers import debug1
 
 def _notify(message):
     addr = os.environ.get("NOTIFY_SOCKET", None)
@@ -12,17 +12,18 @@ def _notify(message):
     
     try:
         sock = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
-    except socket.error as e:
-        debug1("Error creating socket to notify to systemd: %s\n" % e)
+    except (OSError, IOError) as e:
+        debug1("Error creating socket to notify systemd: %s\n" % e)
+        return False
 
-    if not (sock and message): 
+    if not message: 
         return False
 
     assert isinstance(message, bytes)
 
     try:
         return (sock.sendto(message, addr) > 0)
-    except socket.error as e:
+    except (OSError, IOError) as e:
         debug1("Error notifying systemd: %s\n" % e)
         return False
 

sshuttle/tests/client/test_sdnotify.py

+from mock import Mock, patch, call
+import sys
+import io
+import socket
+
+import sshuttle.sdnotify
+
+
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify_invalid_socket_path(mock_get):
+    mock_get.return_value = 'invalid_path'
+    assert not sshuttle.sdnotify.send(sshuttle.sdnotify.ready())
+
+
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify_socket_not_there(mock_get):
+    mock_get.return_value = '/run/valid_nonexistent_path'
+    assert not sshuttle.sdnotify.send(sshuttle.sdnotify.ready())
+
+
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify_no_message(mock_get):
+    mock_get.return_value = '/run/valid_path'
+    assert not sshuttle.sdnotify.send()
+
+
+@patch('sshuttle.sdnotify.socket.socket')
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify_socket_error(mock_get, mock_socket):
+    mock_get.return_value = '/run/valid_path'
+    mock_socket.side_effect = socket.error('test error')
+    assert not sshuttle.sdnotify.send(sshuttle.sdnotify.ready())
+
+
+@patch('sshuttle.sdnotify.socket.socket')
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify_sendto_error(mock_get, mock_socket):
+    message = sshuttle.sdnotify.ready()
+    socket_path = '/run/valid_path'
+
+    sock = Mock()
+    sock.sendto.side_effect = socket.error('test error')
+    mock_get.return_value = '/run/valid_path'
+    mock_socket.return_value = sock
+
+    assert not sshuttle.sdnotify.send(message)
+    assert sock.sendto.mock_calls == [
+        call(message, socket_path),
+    ]
+
+
+@patch('sshuttle.sdnotify.socket.socket')
+@patch('sshuttle.sdnotify.os.environ.get')
+def test_notify(mock_get, mock_socket):
+    messages = [sshuttle.sdnotify.ready(), sshuttle.sdnotify.status('Running')]
+    socket_path = '/run/valid_path'
+
+    sock = Mock()
+    sock.sendto.return_value = 1
+    mock_get.return_value = '/run/valid_path'
+    mock_socket.return_value = sock
+    
+    assert sshuttle.sdnotify.send(*messages)
+    assert sock.sendto.mock_calls == [
+        call(b'\n'.join(messages), socket_path),
+    ]