Fix installer CA port check for port 8080

The installer now checks that port 8080 is available and not in use by
any other application.

The port checker has been rewritten to use bind() rather than just
checking if a server responds on localhost. It's much more reliable and
detects more problems.

Original patch by m3gat0nn4ge.

Co-authored-by: Mega Tonnage <m3gat0nn4ge@gmail.com>
Fixes: https://pagure.io/freeipa/issue/7415
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>

ipatests/test_ipapython/test_ipautil.py

@@ -21,6 +21,7 @@
 """
 Test the `ipapython/ipautil.py` module.
 """
+import socket
 import sys
 import tempfile
 
@@ -508,3 +509,42 @@ def test_run_stderr():
     assert "message" not in str(cm.value)
     assert "message" not in str(cm.value.output)
     assert "message" not in str(cm.value.stderr)
+
+
+@pytest.fixture(scope='function')
+def tcp_listen():
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    try:
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, True)
+        # port 0 means the OS selects a random, unused port for the test.
+        s.bind(('', 0))
+        s.listen(1)
+        yield s.getsockname()[-1], s
+    finally:
+        s.close()
+
+
+@pytest.fixture(scope='function')
+def udp_listen():
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    try:
+        # port 0 means the OS selects a random, unused port for the test.
+        s.bind(('', 0))
+        yield s.getsockname()[-1], s
+    finally:
+        s.close()
+
+
+def test_check_port_bindable_tcp(tcp_listen):
+    port, sock = tcp_listen
+    assert not ipautil.check_port_bindable(port)
+    assert not ipautil.check_port_bindable(port, socket.SOCK_STREAM)
+    sock.close()
+    assert ipautil.check_port_bindable(port)
+
+
+def test_check_port_bindable_udp(udp_listen):
+    port, sock = udp_listen
+    assert not ipautil.check_port_bindable(port, socket.SOCK_DGRAM)
+    sock.close()
+    assert ipautil.check_port_bindable(port, socket.SOCK_DGRAM)