W3CPropagator rejects versions in which either digit is f

[KalleOlaviNiemitalo]

Description

System.Diagnostics.W3CPropagator rejects the received traceparent value if either digit of the two-digit version field is "f". According to https://www.w3.org/TR/2021/REC-trace-context-1-20211123/#version, only the version "ff" is invalid; others like "0f" or "f1" should not be rejected.

Reproduction Steps

TraceParentDemo.csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <OutputType>Exe</OutputType>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="10.0.0-preview.5.25277.114" />
  </ItemGroup>

</Project>

Program.cs:

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace TraceParentDemo
{
    public static class Program
    {
        public static void Main()
        {
            DistributedContextPropagator propagator = DistributedContextPropagator.CreateW3CPropagator();
            propagator.ExtractTraceIdAndState(new object(), GetHeader, out string traceId, out string traceState);
            Console.WriteLine(traceId ?? "Trace ID is not available");
        }

        private static void GetHeader(object carrier, string fieldName, out string fieldValue, out IEnumerable<string> fieldValues)
        {
            switch (fieldName)
            {
                case "traceparent":
                    fieldValue = "0f-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00";
                    fieldValues = null;
                    break;

                default:
                    fieldValue = null;
                    fieldValues = null;
                    break;
            }
        }
    }
}

dotnet run

Expected behavior

The program should output "0f-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00".

Actual behavior

The program outputs "Trace ID is not available".

Regression?

It is somewhat of a regression. Although the DistributedContextPropagator.CreateW3CPropagator() method is new in version 10 of the System.Diagnostics.DiagnosticSource package, the DistributedContextPropagator.Current property was changed to have the same behaviour by default.

Known Workarounds

Derive your own class from DistributedContextPropagator, copy the code from W3CPropagator, and fix the bug.

Configuration

No response

Other information

The impact of this bug is low because W3C has only defined version "00" of the traceparent header so far. I expect it will take several decades before the version reaches "0f".

This code came from #114583. Note the || operator.

runtime/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/W3CPropagator.cs

Lines 609 to 612 in eef526e

	if (traceParent[0] == 'f' || traceParent[1] == 'f' || IsInvalidTraceParentCharacter(traceParent[0]) || IsInvalidTraceParentCharacter(traceParent[1]))
	{
	return true;
	}

Cc: @tarekgh

[KalleOlaviNiemitalo]

This should be in area-System.Diagnostics.Activity.

[dotnet-policy-service]

Tagging subscribers to this area: @steveisok, @dotnet/dotnet-diag
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-diagnostics-activity
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[KalleOlaviNiemitalo]

Activity.IsW3CId(string id) does not have the same bug.

runtime/src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

Lines 1059 to 1078 in eef526e

	/// <summary>
	/// Returns true if 'id' has the format of a WC3 id see https://w3c.github.io/trace-context
	/// </summary>
	private static bool IsW3CId(string id)
	{
	// A W3CId is
	// * 2 hex chars Version (ff is invalid)
	// * 1 char - char
	// * 32 hex chars traceId
	// * 1 char - char
	// * 16 hex chars spanId
	// * 1 char - char
	// * 2 hex chars flags
	// = 55 chars (see https://w3c.github.io/trace-context)
	// The version (00-fe) is used to indicate that this is a WC3 ID.
	return id.Length == 55 &&
	('0' <= id[0] && id[0] <= '9' || 'a' <= id[0] && id[0] <= 'f') &&
	('0' <= id[1] && id[1] <= '9' || 'a' <= id[1] && id[1] <= 'f') &&
	(id[0] != 'f' || id[1] != 'f');
	}