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docker/routlin-dash/app/sanitize.py

@@ -128,6 +128,20 @@ def domainname(value, max_len=253):
     """Hostname or domain: letters, digits, hyphens, dots. Lowercased."""
     return _strip(value.lower(), r'[^a-z0-9\-.]', max_len)
 
+_HOSTNAME_RE = re.compile(r'^[a-z0-9]([a-z0-9_\-]*[a-z0-9])?$')
+
+def hostname(value, max_len=253):
+    """Network hostname: letters, digits, hyphens, underscores. Must start and end with
+    alphanumeric. No consecutive hyphens or underscores. Returns lowercase if valid, None if not."""
+    s = str(value).strip().lower()
+    if not s or len(s) > max_len:
+        return None
+    if re.search(r'[-_]{2,}', s):
+        return None
+    if not _HOSTNAME_RE.match(s):
+        return None
+    return s
+
 def domainlist(lines):
     """Sanitize a list of domain name strings, returning only non-empty results."""
     return [h for v in lines if (h := domainname(v))]