Validate host links with PSL rules

src/common/gen-public-suffix.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+import sys
+import urllib.request
+from pathlib import Path
+
+URL = "https://raw.githubusercontent.com/publicsuffix/list/main/public_suffix_list.dat"
+
+
+def parse_rules(text: str):
+    rules = []
+    for raw in text.splitlines():
+        line = raw.strip()
+        if not line or line.startswith("//"):
+            continue
+        if " " in line or "\t" in line:
+            line = line.split()[0]
+        rules.append(line.lower())
+    return sorted(set(rules))
+
+
+def emit_header(path: str, rules):
+    with open(path, "w", encoding="utf-8", newline="\n") as out:
+        out.write("#pragma once\n")
+        out.write("static const char * const public_suffix_rules[] = {\n")
+        for rule in rules:
+            escaped = rule.replace("\\", "\\\\").replace('"', '\\"')
+            out.write(f'\t"{escaped}",\n')
+        out.write("};\n")
+        out.write(
+            "static const unsigned int public_suffix_rules_len = sizeof(public_suffix_rules) / sizeof(public_suffix_rules[0]);\n"
+        )
+
+
+def main():
+    if len(sys.argv) != 2:
+        raise SystemExit("usage: gen-public-suffix.py <output>")
+    output = Path(sys.argv[1])
+    fallback = Path(__file__).with_name("public_suffix_data.h")
+    try:
+        with urllib.request.urlopen(URL, timeout=30) as resp:
+            data = resp.read().decode("utf-8")
+        rules = parse_rules(data)
+        emit_header(str(output), rules)
+    except Exception:
+        if not fallback.exists():
+            raise
+        output.write_bytes(fallback.read_bytes())
+
+
+if __name__ == "__main__":
+    main()