19026 NGINX web servers (Linux) plugin now supports IPv6

The NGINX web server (Linux) agent plugin now supports IPv6 addresses.
Previously they could not be configured via the GUI and checks using
IPv6 addresses (either due to auto-detection or manual configuration) failed.

Jira: SUP-26587
Change-Id: I95b80790d8329a55fae8d368986ffcda8f408bd0

Author: whme

.werks/19026.md

@@ -0,0 +1,18 @@
+[//]: # (werk v2)
+# NGINX web servers (Linux) plugin now supports IPv6
+
+key        | value
+---------- | ---
+date       | 2026-01-08T09:25:39+00:00
+version    | 2.4.0p19
+class      | feature
+edition    | cee
+component  | agents
+level      | 1
+compatible | yes
+
+NGINX web server (Linux) agent plugin now supports IPv6 addresses.
+
+Previously they could not be configured via the GUI and checks using IPv6 addresses (either due to auto-detection or manual configuration) failed.
+
+With this update, users can configure IPv6 addresses for the NGINX agent plugin via the GUI without encountering errors. Checks using IPv6 addresses will now succeed automatically after the update, requiring no additional action.

agents/plugins/nginx_status.py

@@ -17,6 +17,7 @@
 # create an nginx_status.cfg file in MK_CONFDIR and populate the servers
 # list to prevent executing the detection mechanism.
 
+import ipaddress
 import os
 import re
 import sys
@@ -120,6 +121,21 @@ def try_detect_servers(ssl_ports):
     return results
 
 
+def _is_ip_v6_address(address: str) -> bool:
+    """Check if the given address is an IPv6 address."""
+    try:
+        return ipaddress.ip_address(address).version == 6
+    except ValueError:
+        return False
+
+
+def _make_url(proto: str, address: str, port: int, page: str) -> str:
+    """Construct a URL from its components, taking care of IPv6 addresses."""
+    if _is_ip_v6_address(address):
+        return "%s://[%s]:%s/%s" % (proto, address, port, page)
+    return "%s://%s:%s/%s" % (proto, address, port, page)
+
+
 def main():  # pylint: disable=too-many-branches
     config_dir = os.getenv("MK_CONFDIR", "/etc/check_mk")
     config_file = config_dir + "/nginx_status.cfg"
@@ -155,7 +171,7 @@ def main():  # pylint: disable=too-many-branches
             if proto not in ["http", "https"]:
                 raise ValueError("Scheme '%s' is not allowed" % proto)
 
-            url = "%s://%s:%s/%s" % (proto, address, port, page)
+            url = _make_url(proto, address, port, page)
             # Try to fetch the status page for each server
             try:
                 request = Request(url, headers={"Accept": "text/plain", "User-Agent": USER_AGENT})
@@ -164,9 +180,8 @@ def main():  # pylint: disable=too-many-branches
                 if "SSL23_GET_SERVER_HELLO:unknown protocol" in str(e):
                     # HACK: workaround misconfigurations where port 443 is used for
                     # serving non ssl secured http
-                    url = "http://%s:%s/%s" % (address, port, page)
                     fd = urlopen(  # pylint: disable=consider-using-with
-                        url
+                        _make_url("http", address, port, page)
                     )  # nosec B310 # BNS:6b61d9
                 else:
                     raise