fix(w3c trace context): consider traceparent format version ff invalid

This is a follow up to commit
f283a4b
which added some tests for parsing newer versions. One of the tests used
format version "ff", which the W3C trace context specification
explicitly defines as invalid. This commit fixes that test and also the
regex used for parsing the traceparent header, so that a header with
version ff will be rejected as invalid.

Signed-off-by: Bastian Krol <bastian.krol@ibm.com>

instana/w3c_trace_context/traceparent.py

@@ -9,7 +9,7 @@
 
 class Traceparent:
     SPECIFICATION_VERSION = "00"
-    TRACEPARENT_REGEX = re.compile("^[0-9a-f]{2}-(?!0{32})([0-9a-f]{32})-(?!0{16})([0-9a-f]{16})-[0-9a-f]{2}")
+    TRACEPARENT_REGEX = re.compile("^[0-9a-f][0-9a-e]-(?!0{32})([0-9a-f]{32})-(?!0{16})([0-9a-f]{16})-[0-9a-f]{2}")
 
     def validate(self, traceparent):
         """

tests/w3c_trace_context/test_traceparent.py

@@ -16,13 +16,17 @@ def test_validate_valid(self):
     def test_validate_newer_version(self):
         # Although the incoming traceparent header sports a newer version number, we should still be able to parse the
         # parts that we understand (and consider it valid).
-        traceparent = "ff-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01-12345-abcd"
+        traceparent = "fe-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01-12345-abcd"
         self.assertEqual(traceparent, self.tp.validate(traceparent))
 
     def test_validate_unknown_flags(self):
         traceparent = "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-ee"
         self.assertEqual(traceparent, self.tp.validate(traceparent))
 
+    def test_validate_invalid_traceparent_version(self):
+        traceparent = "ff-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01"
+        self.assertIsNone(self.tp.validate(traceparent))
+
     def test_validate_invalid_traceparent(self):
         traceparent = "00-4bxxxxx3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01"
         self.assertIsNone(self.tp.validate(traceparent))
@@ -48,7 +52,7 @@ def test_get_traceparent_fields_unsampled(self):
     def test_get_traceparent_fields_newer_version(self):
         # Although the incoming traceparent header sports a newer version number, we should still be able to parse the
         # parts that we understand (and consider it valid).
-        traceparent = "ff-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01-12345-abcd"
+        traceparent = "fe-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01-12345-abcd"
         version, trace_id, parent_id, sampled_flag = self.tp.get_traceparent_fields(traceparent)
         self.assertEqual(trace_id, "4bf92f3577b34da6a3ce929d0e0e4736")
         self.assertEqual(parent_id, "00f067aa0ba902b7")