[Network Path] Ignore gopacket unsupported layers to avoid false negatives, fix UDP payload calculation

[ken-schneider]

What does this PR do?

Ignores unsupported layers for all of our packet parsers. While the responses we care about usually won't have additional layers beyond what we're have decoders for, we have seen several cases where a UDP ICMP response to our traceroute has additional layers after the UDP header.

Specifically the problem for Windows UDP traceroutes was that while the outer packet parser ignored unsupported layers, the inner packet parser did not.

The other bug resolved with this PR has to do with the payload calculation for UDP traceroute. Currently, the payload is the same at each TTL leading to an identical UDP checksum. This makes it more difficult to ensure we're matching the right packet with the right TTL and could lead hops being shown at the wrong TTL, especially in a (forthcoming) parallelized traceroute.

Motivation

We've seen this impact UDP traceroutes on Windows.

Describe how you validated your changes

Validated my changes by running TCP and UDP traceroutes on Windows and ensuring that we're still seeing the expected hops. For Linux, I ran TCP traceroute with the agent.

Possible Drawbacks / Trade-offs

Additional Notes

[agent-platform-auto-pr]

Static quality checks ✅

Please find below the results from static quality gates

Info

Result	Quality gate	On disk size	On disk size limit	On wire size	On wire size limit
✅	static_quality_gate_agent_deb_amd64	844.66MiB	858.45MiB	203.53MiB	214.3MiB
✅	static_quality_gate_docker_agent_amd64	929.14MiB	942.69MiB	310.7MiB	321.56MiB

[agent-platform-auto-pr]

Uncompressed package size comparison

Comparison with ancestor d5b752a2a3e4ed0f67e8423cf890a308dd60b86f

Diff per package

package	diff	status	size	ancestor	threshold
datadog-agent-amd64-deb	0.00MB	✅	873.45MB	873.44MB	0.50MB
datadog-agent-x86_64-rpm	0.00MB	✅	883.18MB	883.18MB	0.50MB
datadog-agent-x86_64-suse	0.00MB	✅	883.18MB	883.18MB	0.50MB
datadog-agent-arm64-deb	0.00MB	✅	861.33MB	861.33MB	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	✅	445.70MB	445.70MB	0.50MB
datadog-iot-agent-amd64-deb	0.00MB	✅	86.23MB	86.23MB	0.50MB
datadog-iot-agent-x86_64-rpm	0.00MB	✅	86.30MB	86.30MB	0.50MB
datadog-iot-agent-x86_64-suse	0.00MB	✅	86.30MB	86.30MB	0.50MB
datadog-iot-agent-arm64-deb	0.00MB	✅	82.50MB	82.50MB	0.50MB
datadog-iot-agent-aarch64-rpm	0.00MB	✅	82.57MB	82.57MB	0.50MB
datadog-agent-aarch64-rpm	-0.00MB	✅	871.05MB	871.05MB	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=55126387 --os-family=ubuntu

Note: This applies to commit e4fb533

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 6f3569de-f021-4419-b91f-9fd0610c61b6

Baseline: d5b752a
Comparison: e4fb533
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	+1.45	[-1.65, +4.55]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	+1.06	[+0.98, +1.14]	1	Logs
➖	file_to_blackhole_1000ms_latency	egress throughput	+0.57	[-0.20, +1.34]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	+0.07	[-0.73, +0.86]	1	Logs
➖	file_to_blackhole_0ms_latency_http1	egress throughput	+0.04	[-0.89, +0.98]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.01	[-0.02, +0.04]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	+0.00	[-0.63, +0.63]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.29, +0.27]	1	Logs
➖	quality_gate_idle	memory utilization	-0.02	[-0.04, +0.01]	1	Logs bounds checks dashboard
➖	file_to_blackhole_100ms_latency	egress throughput	-0.02	[-0.73, +0.69]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	-0.03	[-0.89, +0.82]	1	Logs
➖	file_to_blackhole_0ms_latency_http2	egress throughput	-0.08	[-0.98, +0.82]	1	Logs
➖	file_tree	memory utilization	-0.11	[-0.18, -0.04]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.34	[-0.80, +0.12]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	-0.41	[-0.49, -0.34]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	-1.06	[-1.93, -0.19]	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 lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, 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_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.

[ken-schneider]

This is due to us returning the parsed IP header. This doesn't work correctly on macOS because the packet is encoded in network byte order, but the ipv4Header.Parse() function expects the packet to be in macOS's byte order.

Since I want to keep changes with this PR (since I'm planning to backport) to a minimum I'm going to address this in another clean up PR.

[ken-schneider]

/merge

[dd-devflow]

Devflow running: /merge

View all feedbacks in Devflow UI.

---

2025-02-06 16:08:57 UTC ℹ️ MergeQueue: waiting for PR to be ready

This merge request is not mergeable yet, because of pending checks/missing approvals. It will be added to the queue as soon as checks pass and/or get approvals.
Note: if you pushed new commits since the last approval, you may need additional approval.
You can remove it from the waiting list with /remove command.

---

2025-02-06 16:11:30 UTC ℹ️ MergeQueue: merge request added to the queue

The median merge time in main is 29m.

---

2025-02-06 16:46:42 UTC ℹ️ MergeQueue: This merge request was merged

[agent-platform-auto-pr]

The backport to 7.63.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-7.63.x 7.63.x
# Navigate to the new working tree
cd .worktrees/backport-7.63.x
# Create a new branch
git switch --create backport-33719-to-7.63.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 fffa7854b7503559a8f16e66074ec29b43f7e3d3
# Push it to GitHub
git push --set-upstream origin backport-33719-to-7.63.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-7.63.x

Then, create a pull request where the base branch is 7.63.x and the compare/head branch is backport-33719-to-7.63.x.