Allow unknown TLVs to pass through

python_otbr_api/tlv_parser.py

@@ -5,6 +5,9 @@
 from dataclasses import dataclass, field
 from enum import IntEnum
 import struct
+import logging
+
+_LOGGER = logging.getLogger(__name__)
 
 
 class TLVError(Exception):
@@ -124,7 +127,7 @@ def _encode_item(item: MeshcopTLVItem) -> bytes:
     return struct.pack(f"!BB{data_len}s", item.tag, data_len, item.data)
 
 
-def encode_tlv(items: dict[MeshcopTLVType, MeshcopTLVItem]) -> str:
+def encode_tlv(items: dict[MeshcopTLVType | int, MeshcopTLVItem]) -> str:
     """Encode a TLV encoded dataset to a hex string.
 
     Raises if the TLV is invalid.
@@ -137,7 +140,7 @@ def encode_tlv(items: dict[MeshcopTLVType, MeshcopTLVItem]) -> str:
     return result.hex()
 
 
-def _parse_item(tag: MeshcopTLVType, data: bytes) -> MeshcopTLVItem:
+def _parse_item(tag: MeshcopTLVType | int, data: bytes) -> MeshcopTLVItem:
     """Parse a TLV encoded dataset item."""
     if tag == MeshcopTLVType.ACTIVETIMESTAMP:
         return Timestamp(tag, data)
@@ -149,7 +152,7 @@ def _parse_item(tag: MeshcopTLVType, data: bytes) -> MeshcopTLVItem:
     return MeshcopTLVItem(tag, data)
 
 
-def parse_tlv(data: str) -> dict[MeshcopTLVType, MeshcopTLVItem]:
+def parse_tlv(data: str) -> dict[MeshcopTLVType | int, MeshcopTLVItem]:
     """Parse a TLV encoded dataset.
 
     Raises if the TLV is invalid.
@@ -160,19 +163,37 @@ def parse_tlv(data: str) -> dict[MeshcopTLVType, MeshcopTLVItem]:
         raise TLVError("invalid tlvs") from err
     result = {}
     pos = 0
-    while pos < len(data_bytes):
-        try:
-            tag = MeshcopTLVType(data_bytes[pos])
-        except ValueError as err:
-            raise TLVError(f"unknown type {data_bytes[pos]}") from err
+    length = len(data_bytes)
+
+    while pos < length:
+        if pos + 2 > length:
+            raise TLVError("truncated tlv header")
+
+        raw_tag = data_bytes[pos]
         pos += 1
+
+        # Unknown tags should still be passed through
+        tag: MeshcopTLVType | int
+
+        try:
+            tag = MeshcopTLVType(raw_tag)
+        except ValueError:
+            tag = raw_tag
+
         _len = data_bytes[pos]
         pos += 1
+
+        if pos + _len > length:
+            raise TLVError(f"expected {_len} bytes for tag {tag!r}, got {length - pos}")
+
         val = data_bytes[pos : pos + _len]
-        if len(val) < _len:
-            raise TLVError(f"expected {_len} bytes for {tag.name}, got {len(val)}")
         pos += _len
+
+        # Once we have the value, we can log a warning about the unknown TLV
+        if not isinstance(tag, MeshcopTLVType):
+            _LOGGER.warning("unknown TLV type %d=%r", raw_tag, val)
+
         if tag in result:
-            raise TLVError(f"duplicated tag {tag.name}")
+            raise TLVError(f"duplicated tag {tag!r}")
         result[tag] = _parse_item(tag, val)
     return result

tests/test_tlv_parser.py

@@ -47,14 +47,15 @@ def test_encode_tlv() -> None:
         MeshcopTLVType.SECURITYPOLICY: MeshcopTLVItem(
             MeshcopTLVType.SECURITYPOLICY, bytes.fromhex("02a0f7f8")
         ),
+        189: MeshcopTLVItem(189, bytes.fromhex("abcdef")),
     }
     dataset_tlv = encode_tlv(dataset)
     assert (
         dataset_tlv
         == (
             "0E080000000000010000000300000F35060004001FFFE0020811111111222222220708FDAD"
             "70BFE5AA15DD051000112233445566778899AABBCCDDEEFF030E4F70656E54687265616444"
-            "656D6F010212340410445F2B5CA6F2A93A55CE570A70EFEECB0C0402A0F7F8"
+            "656D6F010212340410445F2B5CA6F2A93A55CE570A70EFEECB0C0402A0F7F8BD03ABCDEF"
         ).lower()
     )
 
@@ -64,7 +65,7 @@ def test_parse_tlv() -> None:
     dataset_tlv = (
         "0E080000000000010000000300000F35060004001FFFE0020811111111222222220708FDAD70BF"
         "E5AA15DD051000112233445566778899AABBCCDDEEFF030E4F70656E54687265616444656D6F01"
-        "0212340410445F2B5CA6F2A93A55CE570A70EFEECB0C0402A0F7F8"
+        "0212340410445F2B5CA6F2A93A55CE570A70EFEECB0C0402A0F7F8BD03ABCDEF"
     )
     dataset = parse_tlv(dataset_tlv)
     assert dataset == {
@@ -98,6 +99,7 @@ def test_parse_tlv() -> None:
         MeshcopTLVType.CHANNELMASK: MeshcopTLVItem(
             MeshcopTLVType.CHANNELMASK, bytes.fromhex("0004001fffe0")
         ),
+        189: MeshcopTLVItem(189, bytes.fromhex("abcdef")),
     }
 
 
@@ -138,12 +140,17 @@ def test_parse_tlv_apple() -> None:
         (
             "FF",
             TLVError,
-            "unknown type 255",
+            "truncated tlv header",
+        ),
+        (
+            "FF01",
+            TLVError,
+            "expected 1 bytes for tag 255, got 0",
         ),
         (
             "030E4F70656E54687265616444656D",
             TLVError,
-            "expected 14 bytes for NETWORKNAME, got 13",
+            "expected 14 bytes for tag <MeshcopTLVType.NETWORKNAME: 3>, got 13",
         ),
         (
             "030E4F70656E54687265616444656DFF",