protocol: add generated bindings and conformance fixtures

tools/validate_frames.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+"""Validate the bounded Phase 3A datagram header and fixture corpus."""
+
+from __future__ import annotations
+
+import binascii
+import pathlib
+
+ROOT = pathlib.Path(__file__).resolve().parents[1]
+HEADER_BYTES = 21
+MAX_FRAME_BYTES = 65536
+CHANNEL_LIMITS = {1: 1024, 2: 2048, 3: 65515}
+
+
+def classify(raw: bytes) -> str:
+    if len(raw) < HEADER_BYTES:
+        return "invalid:truncated"
+    if raw[:2] != b"VD":
+        return "invalid:magic"
+    if raw[2] != 1:
+        return "invalid:unsupported_version"
+    if raw[3] not in CHANNEL_LIMITS:
+        return "invalid:unknown_channel"
+    if raw[4] != 0:
+        return "invalid:flags"
+    fragment_index, fragment_count = raw[17], raw[18]
+    if fragment_count == 0 or fragment_index >= fragment_count:
+        return "invalid:fragment"
+    payload_length = int.from_bytes(raw[19:21], "big")
+    if payload_length > CHANNEL_LIMITS[raw[3]]:
+        return "invalid:payload_limit"
+    if len(raw) != HEADER_BYTES + payload_length:
+        return "invalid:length_mismatch"
+    if len(raw) > MAX_FRAME_BYTES:
+        return "invalid:frame_limit"
+    return "valid"
+
+
+def main() -> None:
+    lines = (ROOT / "fixtures/conformance/datagram-v1.tsv").read_text(encoding="utf-8").splitlines()
+    assert lines[0] == "id\tversion\tkind\tinput\texpected"
+    for line in lines[1:]:
+        identifier, version, kind, input_value, expected = line.split("\t")
+        assert kind == "datagram" and version == "1"
+        encoded = input_value.removeprefix("hex=")
+        try:
+            actual = classify(binascii.unhexlify(encoded))
+        except binascii.Error:
+            actual = "invalid:hex"
+        assert actual == expected, f"{identifier}: {actual} != {expected}"
+    print("Datagram frame validation passed")
+
+
+if __name__ == "__main__":
+    main()