RUST-BUG-082: report SX2 answer source counts

Author: Threepwood-7

scripts/rust-live-wire-hideme.py

@@ -140,6 +140,12 @@ def _multipacket_subop_counts(opcode: int, payload: bytes) -> Counter[str]:
     return counts
 
 
+def _answer_sources2_source_count(payload: bytes) -> int | None:
+    if len(payload) < 19:
+        return None
+    return int.from_bytes(payload[17:19], "little")
+
+
 def summarize_source_exchange_packets(packet_dump_dir: Path) -> dict[str, Any]:
     counts: Counter[str] = Counter()
     for dump_file in packet_dump_dir.glob("emulebb-rust-ed2k-tcp-dump-*.jsonl"):
@@ -160,6 +166,18 @@ def summarize_source_exchange_packets(packet_dump_dir: Path) -> dict[str, Any]:
                 counts[f"{direction}RequestSources2"] += 1
             elif opcode_int == OP_ANSWERSOURCES2:
                 counts[f"{direction}AnswerSources2"] += 1
+                payload_hex = str(record.get("payload_hex") or "")
+                try:
+                    payload = bytes.fromhex(payload_hex)
+                except ValueError:
+                    payload = b""
+                source_count = _answer_sources2_source_count(payload)
+                if source_count is None:
+                    counts[f"{direction}MalformedAnswerSources2"] += 1
+                else:
+                    counts[f"{direction}AnswerSources2SourceCount"] += source_count
+                    if source_count == 0:
+                        counts[f"{direction}EmptyAnswerSources2"] += 1
             elif opcode_int in {OP_MULTIPACKET, OP_MULTIPACKET_EXT, OP_MULTIPACKET_EXT2}:
                 payload_hex = str(record.get("payload_hex") or "")
                 try:
@@ -172,6 +190,9 @@ def summarize_source_exchange_packets(packet_dump_dir: Path) -> dict[str, Any]:
     return {
         "requestSources2Sent": counts["sendRequestSources2"] + counts["sendEmbeddedRequestSources2"],
         "answerSources2Received": counts["recvAnswerSources2"],
+        "answerSources2SourceCount": counts["recvAnswerSources2SourceCount"],
+        "emptyAnswerSources2Received": counts["recvEmptyAnswerSources2"],
+        "malformedAnswerSources2Received": counts["recvMalformedAnswerSources2"],
         "embeddedRequestSources2Sent": counts["sendEmbeddedRequestSources2"],
         "standaloneRequestSources2Sent": counts["sendRequestSources2"],
         "counts": dict(sorted(counts.items())),

tests/python/test_rust_live_wire_hideme.py

@@ -62,6 +62,13 @@ def test_source_exchange_summary_counts_embedded_sx2_requests(tmp_path: Path) ->
     module = load_live_wire_module()
     dump_path = tmp_path / "emulebb-rust-ed2k-tcp-dump-test.jsonl"
     request_filename_ext_info = bytes([1, 0, 0, 0, 0])
+    answer_sources2_payload = (
+        bytes([4])
+        + bytes(range(16))
+        + (2).to_bytes(2, "little")
+        + (bytes([192, 0, 2, 1]) + (4662).to_bytes(2, "little") + bytes(23))
+        + (bytes([192, 0, 2, 2]) + (4663).to_bytes(2, "little") + bytes(23))
+    )
     multipacket_ext_payload = (
         bytes(range(16))
         + (12345).to_bytes(8, "little")
@@ -79,7 +86,7 @@ def test_source_exchange_summary_counts_embedded_sx2_requests(tmp_path: Path) ->
         {
             "direction": "recv",
             "opcode": module.OP_ANSWERSOURCES2,
-            "payload_hex": "",
+            "payload_hex": answer_sources2_payload.hex(),
         },
     ]
     dump_path.write_text("\n".join(json.dumps(row) for row in records), encoding="utf-8")
@@ -90,6 +97,8 @@ def test_source_exchange_summary_counts_embedded_sx2_requests(tmp_path: Path) ->
     assert summary["embeddedRequestSources2Sent"] == 1
     assert summary["standaloneRequestSources2Sent"] == 0
     assert summary["answerSources2Received"] == 1
+    assert summary["answerSources2SourceCount"] == 2
+    assert summary["emptyAnswerSources2Received"] == 0
 
 
 def test_source_exchange_summary_counts_ext2_embedded_sx2_requests(tmp_path: Path) -> None:
@@ -120,6 +129,28 @@ def test_source_exchange_summary_counts_ext2_embedded_sx2_requests(tmp_path: Pat
     assert summary["embeddedRequestSources2Sent"] == 1
 
 
+def test_source_exchange_summary_counts_empty_sx2_answers(tmp_path: Path) -> None:
+    module = load_live_wire_module()
+    dump_path = tmp_path / "emulebb-rust-ed2k-tcp-dump-test.jsonl"
+    answer_sources2_payload = bytes([4]) + bytes(range(16)) + (0).to_bytes(2, "little")
+    dump_path.write_text(
+        json.dumps(
+            {
+                "direction": "recv",
+                "opcode": module.OP_ANSWERSOURCES2,
+                "payload_hex": answer_sources2_payload.hex(),
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    summary = module.summarize_source_exchange_packets(tmp_path)
+
+    assert summary["answerSources2Received"] == 1
+    assert summary["answerSources2SourceCount"] == 0
+    assert summary["emptyAnswerSources2Received"] == 1
+
+
 def test_run_downloads_returns_after_first_completion(monkeypatch) -> None:
     module = load_live_wire_module()
     transfer_hashes = [