fix(gotracer): respect context_propagation for Go HTTP/gRPC header in…

[mohd-ibadullah]

Summary

When context_propagation is disabled, Go HTTP/gRPC clients still inject traceparent headers because the Go-specific propagation path only checks kernel capabilities and ignores the configured propagation mode.

This change aligns gotracer behavior with tpinjector and generictracer by requiring header propagation to be explicitly enabled before registering propagation probes or enabling header injection.

Fixes #2276

Changes

• Add headerPropagationEnabled()
• Gate g_bpf_header_propagation on both kernel support and ContextPropagation.HasHeaders()
• Align g_bpf_traceparent_enabled with generictracer
• Register HTTP/gRPC propagation probes only when header propagation is enabled
• Add regression tests covering propagation constants and probe registration

Validation

• Added unit tests for disabled, tcp, headers, and all propagation modes
• Verified probe registration behavior matches configured propagation mode
• Verified Go gRPC instrumentation remains registered independently of propagation mode

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: mohd-ibadullah / name: ibad (fd9bc6e)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.49%. Comparing base (62333b5) to head (54e10c5).
⚠️ Report is 52 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2292      +/-   ##
==========================================
+ Coverage   68.83%   69.49%   +0.65%     
==========================================
  Files         308      317       +9     
  Lines       40127    41228    +1101     
==========================================
+ Hits        27623    28653    +1030     
+ Misses      10977    10973       -4     
- Partials     1527     1602      +75     

Flag	Coverage Δ
integration-test	51.73% <100.00%> (+1.72%)	⬆️
integration-test-arm	28.81% <80.00%> (-0.53%)	⬇️
integration-test-vm-5.15-lts	29.29% <80.00%> (-0.59%)	⬇️
integration-test-vm-6.18-lts	28.74% <80.00%> (-0.20%)	⬇️
k8s-integration-test	39.66% <100.00%> (+0.27%)	⬆️
oats-test	37.02% <100.00%> (-0.05%)	⬇️
unittests	62.26% <80.00%> (-0.32%)	⬇️

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[Copilot]

Pull request overview

This PR fixes Go tracer (gotracer) context propagation behavior so that traceparent header injection (HTTP/1, HTTP/2, gRPC) is only enabled when the configured context_propagation mode includes headers, aligning behavior with tpinjector/generictracer and addressing #2276.

Changes:

• Add headerPropagationEnabled() and use it to gate g_bpf_header_propagation and HTTP/HTTP2 propagation uprobe registration.
• Align g_bpf_traceparent_enabled with generictracer (enabled only when TrackRequestHeaders or any context propagation is enabled).
• Add unit tests covering constants and (some) probe-registration expectations across propagation modes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pkg/internal/ebpf/gotracer/gotracer.go	Gates Go header propagation constants/probes on both kernel capability and ContextPropagation.HasHeaders(), and aligns traceparent parsing enablement with other tracers.
pkg/internal/ebpf/gotracer/gotracer_test.go	Adds regression tests for propagation-related constants and for conditional registration of key HTTP/HTTP2 propagation probes.

Comments suppressed due to low confidence (1)

pkg/internal/ebpf/gotracer/gotracer.go:834

• The new header-propagation gating in GoProbes only wraps the net/http and http2 WriteHeaders probes. Several gRPC header-propagation helper probes (e.g., google.golang.org/grpc/internal/transport.(*http2Client).NewStream return probe, (*controlBuffer).executeAndPut, (*loopyWriter).originateStream) are still registered unconditionally even though their eBPF programs early-return when g_bpf_header_propagation=false. To fully “register propagation probes only when header propagation is enabled” (per PR description) and to avoid unnecessary uprobe attachment overhead, consider moving those gRPC propagation-only probes under the same headerPropagationEnabled() condition (while keeping non-propagation gRPC tracing probes always-on).

	if p.headerPropagationEnabled() {
		m["net/http.Header.writeSubset"] = []*ebpfcommon.ProbeDesc{{
			Start: p.bpfObjects.ObiUprobeWriteSubset, // http 1.x context propagation
		}}
		m["golang.org/x/net/http2.(*Framer).WriteHeaders"] = []*ebpfcommon.ProbeDesc{
			{ // http2 context propagation
				Start: p.bpfObjects.ObiUprobeGolangHttp2FramerWriteHeaders,
				End:   p.bpfObjects.ObiUprobeHttp2FramerWriteHeadersReturns,
			},
			{ // for grpc
				Start: p.bpfObjects.ObiUprobeGrpcFramerWriteHeaders,
				End:   p.bpfObjects.ObiUprobeGrpcFramerWriteHeadersReturns,
			},
		}
		m["net/http.(*http2Framer).WriteHeaders"] = []*ebpfcommon.ProbeDesc{{ // http2 context propagation
			Start: p.bpfObjects.ObiUprobeNetHttp2FramerWriteHeaders,
			End:   p.bpfObjects.ObiUprobeHttp2FramerWriteHeadersReturns,
		}}
	}

[mmat11]

looks like a lot of tests are failing, they probably need explicit config for headers context propagation

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

pkg/internal/ebpf/gotracer/gotracer.go:113

• The CAP_SYS_ADMIN/lockdown log in LoadSpecs() is emitted even when header propagation is not requested (e.g., context_propagation: disabled or tcp). Since this message is specifically about Go library-level header injection support, it’s misleading/noisy unless header propagation is enabled in config. Consider gating the log behind ContextPropagation.HasHeaders() so users don’t see propagation warnings when they’ve explicitly disabled it (or enabled tcp-only propagation).

func (p *Tracer) LoadSpecs() ([]*ebpfcommon.SpecBundle, error) {
	if !p.supportsContextPropagation() {
		p.log.Info("Kernel in lockdown mode or missing CAP_SYS_ADMIN.")
	}

[mmat11]

needs linter fix and copilot comment looks valid, lgtm after that