Handling malformed messages

- Set a default type and subtype as DLT_LOG
when extended header is not provided
- Add test to a malformed message

Author: Ahmed Haggag

dlt/core/core_base.py

@@ -211,9 +211,15 @@ def use_extended_header(self):
         """Returns True if the DLTMessage has extended header"""
         return self.standardheader.htyp & DLT_HTYP_UEH
 
+    @property
+    def _is_extended_header_exists(self):
+        return self.extendedheader and self.extendedheader.msin
+
     @property
     def is_mode_verbose(self):
         """Returns True if the DLTMessage is set to verbose mode"""
+        if not self._is_extended_header_exists:
+            return self.verbose
         return self.extendedheader.msin & DLT_MSIN_VERB
 
     @property
@@ -290,6 +296,8 @@ def ctrl_return_type_string(self):
     @property
     def type(self):
         """Returns message type of the DLTMessage"""
+        if not self._is_extended_header_exists:
+            return DLT_TYPE_LOG
         return (self.extendedheader.msin & DLT_MSIN_MSTP) >> DLT_MSIN_MSTP_SHIFT
 
     @property
@@ -301,6 +309,8 @@ def type_string(self):
     @property
     def subtype(self):
         """Returns message subtype of the DLTMessage"""
+        if not self._is_extended_header_exists:
+            return DLT_TYPE_LOG
         return (self.extendedheader.msin & DLT_MSIN_MTIN) >> DLT_MSIN_MTIN_SHIFT
 
     @property
@@ -329,7 +339,7 @@ def payload_decoded(self):
         """
         text = b""
         if self.is_mode_non_verbose and not self.is_type_control and self.noar == 0:
-            buf = ctypes.create_string_buffer("\000" * DLT_DAEMON_TEXTSIZE)
+            buf = ctypes.create_string_buffer(b"\000" * DLT_DAEMON_TEXTSIZE)
             dltlib.dlt_message_payload(ctypes.byref(self), buf, DLT_DAEMON_TEXTSIZE, DLT_OUTPUT_ASCII, self.verbose)
             return b"[%s] #%s#" % (self.message_id_string, buf.value[4:].rstrip(b"\000"))
 

tests/dlt_message_unit_test.py

@@ -8,10 +8,25 @@
 import pytest
 
 from dlt.dlt import DLTMessage
-from tests.utils import create_messages, stream_one, stream_with_params, stream_multiple, msg_benoit, control_one
+from tests.utils import (
+    create_messages,
+    stream_one,
+    stream_with_params,
+    stream_multiple,
+    stream_multiple_with_malformed_message_at_begining,
+    msg_benoit,
+    control_one,
+)
 
 
 class TestsDLTMessageUnit(object):
+    def test_malformed_message(self):
+        msgs = create_messages(stream_multiple_with_malformed_message_at_begining, from_file=True)
+
+        assert msgs[0].message_id == 1279675715
+        assert len(msgs) == 3
+        assert not msgs[0].extendedheader
+
     def test_compare_default_attrs(self):
         attrs = {"extendedheader.apid": "DA1", "extendedheader.ctid": "DC1"}
         msg = create_messages(stream_one)

tests/utils.py

@@ -11,6 +11,7 @@
 
 
 stream_one = io.BytesIO(b"5\x00\x00 MGHS\xdd\xf6e\xca&\x01DA1\x00DC1\x00\x02\x0f\x00\x00\x00\x02\x00\x00\x00\x00")
+
 stream_with_params = (
     b"DLT\x01\xc2<\x85W\xc7\xc5\x02\x00MGHS=r\x00\xa0MGHS\x00\x00\x02B\x00X\xd4\xf1A\x08"
     b"ENV\x00LVLM\x00\x02\x00\x00-\x00CLevelMonitor::notification() => commandType\x00#"
@@ -30,6 +31,20 @@
     b" currently available 3.7G of space).\nEnforced usage limit is thus 385.9M.\x00"
 )
 
+stream_multiple_with_malformed_message_at_begining = (
+    b"DLT\x01\xfar\xc5c\xf7j\x03\x00\x00\x00\x00\x00\x00\x00\x00LCMFLOW WUP invalidDLT\x01"
+    b"\xfar\xc5c\x0bo\x03\x00XORA'\x01\x00\x1bXORA\x16\x02\x00\x00\x00\x00\x00\x00\x00"
+    b"\x00\x00\x00\x00\x11\x04\x00\x00\x00\x00DLT\x01\xfar\xc5c?o\x03"
+    b"DLT\x01#o\xd1WD>\x0c\x00MGHS5\x00\x00YMGHS\x00\x01\x80\xd1&\x01DA1\x00DC1\x00\x03\x00\x00\x00"
+    b"\x07\x01\x00SYS\x00\x01\x00FILE\xff\xff\x16\x00File transfer manager.\x12\x00"
+    b"DLT System ManagerremoDLT\x01#o\xd1Wo>\x0c\x00MGHS=\x00\x01PMGHS\x00\x00\x03\xf4\x00"
+    b"\x01i\xa6A\x05SYS\x00JOUR\x00\x02\x00\x00\x1b\x002011/11/11 11:11:18.005274\x00\x00\x02\x00\x00"
+    b"\t\x006.005274\x00\x00\x02\x00\x00\x16\x00systemd-journal[748]:\x00\x00\x02\x00\x00\x0f\x00"
+    b"Informational:\x00\x00\x02\x00\x00\xcf\x00Runtime journal (/run/log/journal/) is currently"
+    b" using 8.0M.\nMaximum allowed usage is set to 385.9M.\nLeaving at least 578.8M free (of"
+    b" currently available 3.7G of space).\nEnforced usage limit is thus 385.9M.\x00"
+)
+
 msg_benoit = (
     b"DLT\x01\xa5\xd1\xceW\x90\xb9\r\x00MGHS=\x00\x00RMGHS\x00\x00\n[\x00\x0f\x9b#A\x01DEMODATA\x00"
     b"\x82\x00\x002\x00Logging from the constructor of a global instance\x00"