[NPM-4140] Fix test failures that appear in KMT

[pimlu]

What does this PR do?

This PR fixes test failures that only appeared once I turned on KMT:

1. Disables ProtocolClassificationEnabled in ebpfless (since the same global config is used by all tests, and it seems some config currently "leaks" between tests... we should look into that later)
2. Changes the query pattern for findConnection -- previously it would take the first connection it found and keep that forever. For ebpfless, it needs to replace that connection if it gets newer data.
3. Changes to TestShortWrite -- something strange happened with this one. After setting SO_SNDBUF to 5000, you would expect it to buffer that much writes (the kernel actually sets SO_SNDBUF to 10k, so you would expect 10KB of buffer). But that depends on the kernel apparently. I was only able to fix it by draining the read-end at the final phase of the test. If that's not the right thing to do let me know - we should probably do a quick call since this is hard to explain.
   • In ubuntu 22.04 (kernel 5.15.0), it lets you write 42741 bytes before it's full. And it will really send all that over the wire.
   • But in ubuntu 24.04 (kernel 6.8.0), it still lets you write 42741 bytes, but only 10KB travels over the wire and then it stops progressing until you read from the other end.

Motivation

Turning on kernel matrix testing

Describe how you validated your changes

Ebpfless test suite should still passs:

DD_REMOTE_CONFIGURATION_ENABLED=false TEST_EBPFLESS_OVERRIDE=true sudo -E go test -tags=linux,linux_bpf,npm,process,test ./pkg/network/tracer -v --run TestTracerSuite/eBPFless

KMT should pass in this stacked PR: [NPM-4140] Enable ebpfless tests in CI/KMT

Possible Drawbacks / Trade-offs

Additional Notes

[agent-platform-auto-pr]

Uncompressed package size comparison

Comparison with ancestor 9547dfc03072f74ca030a69a7db3fbaa3e042783

Diff per package

package	diff	status	size	ancestor	threshold
datadog-agent-amd64-deb	0.00MB	✅	928.92MB	928.92MB	0.50MB
datadog-agent-x86_64-rpm	0.00MB	✅	938.66MB	938.66MB	0.50MB
datadog-agent-x86_64-suse	0.00MB	✅	938.66MB	938.66MB	0.50MB
datadog-agent-arm64-deb	0.00MB	✅	916.09MB	916.09MB	0.50MB
datadog-agent-aarch64-rpm	0.00MB	✅	925.81MB	925.81MB	0.50MB
datadog-dogstatsd-amd64-deb	0.00MB	✅	59.01MB	59.01MB	0.50MB
datadog-dogstatsd-x86_64-rpm	0.00MB	✅	59.09MB	59.09MB	0.50MB
datadog-dogstatsd-x86_64-suse	0.00MB	✅	59.09MB	59.09MB	0.50MB
datadog-dogstatsd-arm64-deb	0.00MB	✅	56.50MB	56.50MB	0.50MB
datadog-heroku-agent-amd64-deb	0.00MB	✅	477.89MB	477.89MB	0.50MB
datadog-iot-agent-amd64-deb	0.00MB	✅	93.88MB	93.88MB	0.50MB
datadog-iot-agent-x86_64-rpm	0.00MB	✅	93.95MB	93.95MB	0.50MB
datadog-iot-agent-x86_64-suse	0.00MB	✅	93.95MB	93.95MB	0.50MB
datadog-iot-agent-arm64-deb	0.00MB	✅	89.93MB	89.93MB	0.50MB
datadog-iot-agent-aarch64-rpm	0.00MB	✅	90.00MB	90.00MB	0.50MB

Decision

✅ Passed

[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=53949978 --os-family=ubuntu

Note: This applies to commit 511d7bb

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 37a5b7ec-3f65-4912-8a15-cd59e69b4521

Baseline: 9547dfc
Comparison: 511d7bb
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_logs	% cpu utilization	+3.40	[+0.30, +6.51]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+0.45	[+0.41, +0.50]	1	Logs bounds checks dashboard
➖	file_tree	memory utilization	+0.36	[+0.31, +0.41]	1	Logs
➖	quality_gate_idle	memory utilization	+0.35	[+0.31, +0.39]	1	Logs bounds checks dashboard
➖	file_to_blackhole_0ms_latency	egress throughput	+0.08	[-0.77, +0.93]	1	Logs
➖	file_to_blackhole_0ms_latency_http2	egress throughput	+0.03	[-0.88, +0.93]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.02	[-0.76, +0.81]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	+0.01	[-0.63, +0.64]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	+0.00	[-0.67, +0.67]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.01	[-0.03, +0.01]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	-0.01	[-0.87, +0.84]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.30, +0.27]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.26	[-0.73, +0.21]	1	Logs
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	-0.44	[-1.31, +0.43]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.88	[-0.95, -0.82]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	-1.81	[-2.61, -1.01]	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_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 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, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.