misc masquerade fixes

[Fredi-raspall]

• Contains logging improvements and clean-up in masquerading code
• Improves logic to admit / deny existing masquerading flows on reconfigs.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

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Run ID: 28aba09a-9395-4b38-84f1-2cc23f0fcc80

📥 Commits

Reviewing files that changed from the base of the PR and between ea41ce1 and 123b742.

📒 Files selected for processing (1)

• nat/src/masquerade/flows.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• nat/src/masquerade/flows.rs

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📝 Walkthrough

Walkthrough

Changes

Masquerade allocation now uses destination VPC discriminants consistently, reports missing pools distinctly, adjusts reservation logging, and validates both NAT coverage and source-IP inclusion when checking existing masquerading flows.

Masquerade allocation and flow validation

Layer / File(s)	Summary
Allocation errors and pool-key identity nat/src/masquerade/allocation.rs, nat/src/masquerade/apalloc/{mod.rs,display.rs,test_alloc.rs}	Adds NoPoolFound, updates error classification, and uses dst_vpcd consistently for pool keys, display, lookup, and tests.
Pool reservation handling nat/src/masquerade/apalloc/{mod.rs,port_alloc.rs}	IPv4 and IPv6 reservations return NoPoolFound when pools are absent, with consolidated reservation and updated denial logging.
Masquerading flow compatibility nat/src/masquerade/flows.rs	Re-reservation logs include additional context, and expose checks require both masquerade-range coverage and source-IP inclusion.

Possibly related PRs

• githedgehog/dataplane#1598: Modifies the same masquerading flow compatibility logic.
• githedgehog/dataplane#1628: Modifies the same peering and expose compatibility path.

Suggested reviewers: qmonnet

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	The title is related but too generic to identify the main change.	Rename it to describe the primary change, such as masquerading flow reconfiguration fixes.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description matches the PR's logging and masquerading-flow reconfiguration changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@nat/src/masquerade/flows.rs`:
- Around line 121-130: The masquerade flow-retention check in the peering
`valexp()` loop must honor negative ranges before retaining a flow. Update the
`nat.as_range` and `expose.ips()` matching logic to use the effective expose
matcher or otherwise reject IPs covered by `nat.not_as` and source IPs covered
by `expose.nots`, while preserving the existing positive-range requirements.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ab46ef3f-33cc-48f4-8fda-d389a5498a04

📥 Commits

Reviewing files that changed from the base of the PR and between fcb9dd8 and a5511d6.

📒 Files selected for processing (6)

• nat/src/masquerade/allocation.rs
• nat/src/masquerade/apalloc/display.rs
• nat/src/masquerade/apalloc/mod.rs
• nat/src/masquerade/apalloc/port_alloc.rs
• nat/src/masquerade/apalloc/test_alloc.rs
• nat/src/masquerade/flows.rs

[Copilot]

Pull request overview

This PR refines the NAT masquerade subsystem’s reconfiguration behavior and observability, focusing on clearer logging and more accurate validation of whether existing masqueraded flows remain admissible after config changes.

Changes:

• Adjust flow revalidation logic to require both the existing masquerade IP and the flow source IP to still be permitted by a matching expose during reconfig.
• Improve/standardize allocator and flow logging, and add a dedicated NoPoolFound allocator error for re-reserve paths.
• Rename allocator pool table key field dst_id → dst_vpcd for clarity/consistency (including tests and display output).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
nat/src/masquerade/flows.rs	Tightens reconfig validation for existing masquerade flows and improves related logging.
nat/src/masquerade/apalloc/test_alloc.rs	Updates tests to match dst_vpcd field rename.
nat/src/masquerade/apalloc/port_alloc.rs	Minor logging tweak for explicit well-known port reservation denial.
nat/src/masquerade/apalloc/mod.rs	Renames pool key field; improves re-reserve behavior with NoPoolFound and warn-level logging.
nat/src/masquerade/apalloc/display.rs	Updates display output to match dst_vpcd rename.
nat/src/masquerade/allocation.rs	Adjusts error messages and introduces NoPoolFound mapped to DoneReason::Filtered.

[qmonnet]

Would be cleaner with early exit here instead:

        if !alloced_ip_valid {
            debug!("Flow is no longer valid for masquerading between {src_vpcd} -- {dst_vpcd}");
            flow_info.invalidate_pair();
            return;
        }
        if !compatible_expose_found {
            debug!("Masquerade ip {ip} is no longer allowed over peering {src_vpcd} -- {dst_vpcd}");
            flow_info.invalidate_pair();
            return;
        }

Then less indent for the last block - the code would be less nested, the conditions easier to follow.

[Fredi-raspall]

Fixed