test: fix addnode functional test failure on OpenBSD

This is the functional test counterpart of PR bitcoin#28891 /
commit 007d6f0.

test/functional/rpc_net.py

@@ -9,6 +9,7 @@
 
 from decimal import Decimal
 from itertools import product
+import platform
 import time
 
 import test_framework.messages
@@ -220,8 +221,10 @@ def test_addnode_getaddednodeinfo(self):
         ip_port = "127.0.0.1:{}".format(p2p_port(2))
         self.nodes[0].addnode(node=ip_port, command='add')
         # try to add an equivalent ip
-        ip_port2 = "127.1:{}".format(p2p_port(2))
-        assert_raises_rpc_error(-23, "Node already added", self.nodes[0].addnode, node=ip_port2, command='add')
+        # (note that OpenBSD doesn't support the IPv4 shorthand notation with omitted zero-bytes)
+        if platform.system() != "OpenBSD":
+            ip_port2 = "127.1:{}".format(p2p_port(2))
+            assert_raises_rpc_error(-23, "Node already added", self.nodes[0].addnode, node=ip_port2, command='add')
         # check that the node has indeed been added
         added_nodes = self.nodes[0].getaddednodeinfo()
         assert_equal(len(added_nodes), 1)