improve get_own_ip

posttroll/publisher.py

@@ -12,17 +12,36 @@
 
 
 def get_own_ip():
-    """Get the host's ip number."""
+    """Get the host's ip number.
+
+    Tries multiple methods to determine the host's IP address:
+    1. Connect to an external server (8.8.8.8:80) to determine the outgoing IP
+    2. Resolve the local hostname
+    3. Fall back to localhost (127.0.0.1)
+    """
+    # Method 1: Connect to external server to get outgoing IP
     sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
     try:
         sock.connect(("8.8.8.8", 80))
-    except socket.gaierror:
-        ip_ = "127.0.0.1"
-    else:
         ip_ = sock.getsockname()[0]
+        return ip_
+    except (socket.gaierror, OSError):
+        # Network not available or unreachable
+        pass
     finally:
         sock.close()
-    return ip_
+
+    # Method 2: Try to resolve local hostname
+    try:
+        hostname = socket.gethostname()
+        ip_ = socket.gethostbyname(hostname)
+        if ip_ and ip_ != "127.0.0.1":
+            return ip_
+    except (socket.gaierror, OSError):
+        pass
+
+    # Method 3: Fall back to localhost
+    return "127.0.0.1"
 
 
 class Publisher:

posttroll/tests/test_pubsub.py

@@ -1,6 +1,7 @@
 """Test the publishing and subscribing facilities."""
 
 import logging
+import socket
 import time
 import unittest
 from contextlib import contextmanager
@@ -46,6 +47,68 @@ def free_port():
     return portnum
 
 
+def test_get_own_ip_uses_socket_outgoing_address():
+    """Use the outgoing socket address when external connect succeeds."""
+    from posttroll import publisher as publisher_module
+
+    mocked_sock = mock.Mock()
+    mocked_sock.getsockname.return_value = ("10.1.2.3", 12345)
+
+    with mock.patch("posttroll.publisher.socket.socket", return_value=mocked_sock):
+        assert publisher_module.get_own_ip() == "10.1.2.3"
+
+    mocked_sock.connect.assert_called_once_with(("8.8.8.8", 80))
+    mocked_sock.close.assert_called_once()
+
+
+def test_get_own_ip_falls_back_to_hostname_resolution_on_oserror():
+    """If external connect fails, use resolved hostname ip when available."""
+    from posttroll import publisher as publisher_module
+
+    mocked_sock = mock.Mock()
+    mocked_sock.connect.side_effect = OSError("network unreachable")
+
+    with (
+        mock.patch("posttroll.publisher.socket.socket", return_value=mocked_sock),
+        mock.patch("posttroll.publisher.socket.gethostname", return_value="my-host"),
+        mock.patch("posttroll.publisher.socket.gethostbyname", return_value="192.168.1.50"),
+    ):
+        assert publisher_module.get_own_ip() == "192.168.1.50"
+
+    mocked_sock.close.assert_called_once()
+
+
+@pytest.mark.parametrize(
+    "hostname_side_effect,hostname_ip",
+    [
+        (None, "127.0.0.1"),
+        (socket.gaierror("lookup failed"), None),
+    ],
+    ids=["hostname_returns_loopback", "hostname_lookup_raises"],
+)
+def test_get_own_ip_returns_localhost_when_no_non_loopback_ip(hostname_side_effect, hostname_ip):
+    """Return localhost when external lookup fails and no usable host ip exists."""
+    from posttroll import publisher as publisher_module
+
+    mocked_sock = mock.Mock()
+    mocked_sock.connect.side_effect = OSError("network unreachable")
+    gethostbyname_mock = mock.Mock()
+    if hostname_side_effect is not None:
+        gethostbyname_mock.side_effect = hostname_side_effect
+    else:
+        gethostbyname_mock.return_value = hostname_ip
+
+    with (
+        mock.patch("posttroll.publisher.socket.socket", return_value=mocked_sock),
+        mock.patch("posttroll.publisher.socket.gethostname", return_value="my-host"),
+        mock.patch("posttroll.publisher.socket.gethostbyname", gethostbyname_mock),
+    ):
+        assert publisher_module.get_own_ip() == "127.0.0.1"
+
+    gethostbyname_mock.assert_called_once_with("my-host")
+    mocked_sock.close.assert_called_once()
+
+
 class TestPubSub(unittest.TestCase):
     """Testing the publishing and subscribing capabilities."""