[afpacket] Fix race with Close() seen in CI

[pimlu]

Sister PR in gopacket: Separate Stop() from Close()

What does this PR do?

Unfortunately there's a race I missed in Allow Close() to cancel ZeroCopyReadPacketData: The []byte returned by ZeroCopyReadPacketData() is mmapped, not garbage collected, so it's unsafe to Close() a TPacket while that's still in use.

Rarely, tests would segfault after it tries to read from the unmapped page.

Motivation

Fix CI

Describe how you validated your changes

Run TestTCPCollectionDisabled 500 times, it should not segfault:

DD_REMOTE_CONFIGURATION_ENABLED=false sudo -E go test -race -count 500 -tags=linux,linux_bpf,npm,process,test ./pkg/network/tracer -v --run TestTracerSuite/eBPFless/TestTCPCollectionDisabled

Possible Drawbacks / Trade-offs

Additional Notes

[agent-platform-auto-pr]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv aws.create-vm --pipeline-id=54913051 --os-family=ubuntu

Note: This applies to commit 1bceddc

[agent-platform-auto-pr]

Uncompressed package size comparison

Comparison with ancestor f14e02a0cdfdcdd553a9fe637d6267e6337eff4f

Diff per package

package	diff	status	size	ancestor	threshold
datadog-agent-amd64-deb	0.01MB	⚠️	873.45MB	873.44MB	0.50MB
datadog-agent-x86_64-rpm	0.01MB	⚠️	883.19MB	883.18MB	0.50MB
datadog-agent-x86_64-suse	0.01MB	⚠️	883.19MB	883.18MB	0.50MB
datadog-agent-arm64-deb	0.00MB	✅	861.33MB	861.33MB	0.50MB
datadog-agent-aarch64-rpm	0.00MB	✅	871.05MB	871.05MB	0.50MB
datadog-dogstatsd-amd64-deb	0.00MB	✅	59.09MB	59.09MB	0.50MB
datadog-dogstatsd-x86_64-rpm	0.00MB	✅	59.16MB	59.16MB	0.50MB
datadog-dogstatsd-x86_64-suse	0.00MB	✅	59.16MB	59.16MB	0.50MB
datadog-dogstatsd-arm64-deb	0.00MB	✅	56.56MB	56.56MB	0.50MB
datadog-heroku-agent-amd64-deb	0.00MB	✅	445.68MB	445.68MB	0.50MB
datadog-iot-agent-amd64-deb	0.00MB	✅	86.22MB	86.22MB	0.50MB
datadog-iot-agent-x86_64-rpm	0.00MB	✅	86.29MB	86.29MB	0.50MB
datadog-iot-agent-x86_64-suse	0.00MB	✅	86.29MB	86.29MB	0.50MB
datadog-iot-agent-arm64-deb	0.00MB	✅	82.49MB	82.49MB	0.50MB
datadog-iot-agent-aarch64-rpm	0.00MB	✅	82.56MB	82.56MB	0.50MB

Decision

⚠️ Warning

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: bac49555-6534-4c76-aa3d-7784b0a23dce

Baseline: f14e02a
Comparison: 1bceddc
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_idle	memory utilization	+0.35	[+0.32, +0.39]	1	Logs bounds checks dashboard
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.35	[-0.42, +1.12]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+0.05	[-0.01, +0.12]	1	Logs bounds checks dashboard
➖	file_to_blackhole_0ms_latency_http2	egress throughput	+0.04	[-0.86, +0.94]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.03	[-0.75, +0.81]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.27, +0.29]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.01, +0.01]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.02	[-0.68, +0.63]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	-0.03	[-0.86, +0.80]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	-0.03	[-0.67, +0.61]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.04	[-0.85, +0.78]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.08	[-0.54, +0.38]	1	Logs
➖	file_tree	memory utilization	-0.16	[-0.23, -0.09]	1	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	-0.69	[-1.56, +0.18]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.89	[-1.02, -0.75]	1	Logs
➖	quality_gate_logs	% cpu utilization	-1.70	[-4.73, +1.32]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http1	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http1	memory_usage	10/10
✅	file_to_blackhole_0ms_latency_http2	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency_http2	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency_linear_load	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_300ms_latency	lost_bytes	10/10
✅	file_to_blackhole_300ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10
✅	quality_gate_logs	lost_bytes	10/10
✅	quality_gate_logs	memory_usage	10/10

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.