OCPBUGS-99208: iptables-alerter: ignore Azure Monitor Agent rules - #3088
OCPBUGS-99208: iptables-alerter: ignore Azure Monitor Agent rules#3088danwinship wants to merge 1 commit into
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@danwinship: This pull request references Jira Issue OCPBUGS-99208, which is invalid:
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Summary by CodeRabbit
WalkthroughThe iptables alerter now excludes rules containing Changesiptables alerter filtering
Estimated code review effort: 1 (Trivial) | ~2 minutes Merge Risk: ⚪ Minimal · up to This is a localized change to suppress known Azure Monitor Agent iptables alerts; no actionable merge-blocking risk remains after normal checks and review. Suggested reviewers: ✅ Pre-merge checks override appliedThe pre-merge checks have been overridden successfully. You can now proceed with the merge. Overridden by ❌ Failed checks (2 errors, 1 inconclusive)
✅ Passed checks (21 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: danwinship The full list of commands accepted by this bot can be found here. The pull request process is described here DetailsNeeds approval from an approver in each of these files:
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@danwinship: This pull request references Jira Issue OCPBUGS-99208, which is valid. The bug has been moved to the POST state. 3 validation(s) were run on this bug
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Inline comments:
In `@bindata/network/iptables-alerter/002-script.yaml`:
- Line 40: Reuse the existing 127.0.0.1:8421 exclusion in the per-pod iptables
scan around the pod-selection pipeline at lines 80-83, not only in the
node-level pre-scan. Ensure pod rules containing only the Azure Monitor Agent
endpoint are filtered out before reporting a false-positive event.
- Line 40: Update the iptables filtering pipeline to remove the inline comment
from the continuation line and replace the grep-based 127.0.0.1:8421 exclusion
with an awk filter that handles all-matching exclusions without causing pipefail
failure; place any explanatory comment on its own line.
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@danwinship: This pull request references Jira Issue OCPBUGS-99208, which is valid. 3 validation(s) were run on this bug
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Actionable comments posted: 1
🤖 Prompt for all review comments with AI agents
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Inline comments:
In `@bindata/network/iptables-alerter/002-script.yaml`:
- Around line 36-41: Add a Go *_test.go file for the 002-script.yaml iptables
alerter script, covering both pre-scan filters: excluding rules containing
127.0.0.1:8421 and selecting the first rule beginning with -A. Verify the script
produces the expected output for both cases.
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| (nsenter -n -t "${netns_pid}" iptables-save || true; | ||
| nsenter -n -t "${netns_pid}" ip6tables-save || true) 2>/dev/null | \ | ||
| awk '/^-A/ {print; exit}' | ||
| awk '/127\.0\.0\.1:8421/ {next} /^-A/ {print; exit}' |
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what is running at 8421 ? is it a http endpoint from azure monitor agent pod ?
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For iptables-alerter's purposes, it's not important what the rule actually does. This is just saying that the "warn about pods that use iptables rules" policy doesn't apply to rules that look like that.
(OCPBUGS-99208 has the full rules in question:
iptables -t nat -A OUTPUT -p tcp -d 169.254.169.254 --dport 80 -j DNAT --to-destination 127.0.0.1:8421
iptables -t nat -A PREROUTING -p tcp -d 169.254.169.254 --dport 80 -j DNAT --to-destination 127.0.0.1:8421
so yes, they're intercepting calls (within their own pod) to the cloud metadata server on 169.254.169.254 and redirecting them to a server within the pod, for some reason.)
3 participants
In (some?) ARO clusters, there is an upstream Azure Monitor Agent that creates iptables rules in its pods. There's a bug telling the ARO team they need to get rid of them (https://redhat.atlassian.net/browse/OCPBUGS-99624). Make CNO ignore them now rather than logging errors about them (since it's not something end users can fix).