Allow raw ip addresses

app/checker.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import contextlib
 import dataclasses
 import logging
 import time
@@ -32,19 +33,26 @@ def check_endpoint(ep, default_timeout: float, timestamp_ns: int) -> CheckResult
     timeout = ep.timeout_seconds or default_timeout
     start = time.monotonic()
 
-    try:
-        resolved_ip = dns_resolver.resolve(ep.host, ep.dns_server, timeout)
-    except dns.exception.DNSException as e:
-        return CheckResult(
-            endpoint_name=ep.name, host=ep.host, scheme=ep.scheme, port=ep.port,
-            success=False, status_code=None, expected_status=ep.expected_status,
-            response_time_ms=None, resolved_ip=None,
-            error=f"dns_error: {e}", timestamp_ns=timestamp_ns,
-        )
+    if dns_resolver.is_ip_literal(ep.host):
+        # Nothing to resolve — connect straight to the given IP. dns_server
+        # is not required/used in this case (see config.py).
+        resolved_ip = ep.host
+        pin = contextlib.nullcontext()
+    else:
+        try:
+            resolved_ip = dns_resolver.resolve(ep.host, ep.dns_server, timeout)
+        except dns.exception.DNSException as e:
+            return CheckResult(
+                endpoint_name=ep.name, host=ep.host, scheme=ep.scheme, port=ep.port,
+                success=False, status_code=None, expected_status=ep.expected_status,
+                response_time_ms=None, resolved_ip=None,
+                error=f"dns_error: {e}", timestamp_ns=timestamp_ns,
+            )
+        pin = dns_resolver.pin_resolution(ep.host, resolved_ip)
 
-    url = f"{ep.scheme}://{ep.host}:{ep.port}{ep.path}"
+    url = f"{ep.scheme}://{dns_resolver.format_host_for_url(ep.host)}:{ep.port}{ep.path}"
     try:
-        with dns_resolver.pin_resolution(ep.host, resolved_ip):
+        with pin:
             resp = requests.get(
                 url, timeout=timeout, verify=ep.verify_tls, allow_redirects=True
             )