Fix flaky IP assignment

[neddp]

What is this change about?

Follow-up fix to #2657 to eliminate residual flaky behaviour in IP allocation from reserved CIDR ranges.

PR #2657 fixed the algorithmic logic in find_next_available_ip (pruning by last address, using overlaps?, capturing blocking_ip before mutation). However, the very second integration run in Concourse failed. It looks like the issue is still present under under certain Ruby hash seeds:

Changes:

• IpAddrOrCidr#eql?: now compares both to_i and prefix directly, treating objects with the same base address but different prefix lengths as distinct
• IpAddrOrCidr#hash: now uses [to_i, prefix].hash to satisfy the contract
• find_next_available_ip sort key: changed from ip.to_i to [ip.to_i, ip.prefix] so larger blocks (smaller prefix) always sort before the /32s they contain

Please provide contextual information.

• Fixes flakiness missed by Fix IP Allocation Bug: Reserved Range Not Detected #2657
• The CI failure that prompted this investigation: https://bosh.ci.cloudfoundry.org/teams/main/pipelines/bosh-director/jobs/unit-director-sqlite/builds/581

 -#<Bosh::Director::IpAddrOrCidr:0x000076df19e9bb18
 - @ipaddr=#<IPAddr: IPv4:10.0.11.41/255.255.255.255>>
 +#<Bosh::Director::IpAddrOrCidr:0x000076df19f33760
 + @ipaddr=#<IPAddr: IPv4:10.0.11.34/255.255.255.255>>

 -#<Bosh::Director::IpAddrOrCidr:0x000076df199f91f0
 - @ipaddr=#<IPAddr: IPv4:10.0.11.36/255.255.255.255>>
 +#<Bosh::Director::IpAddrOrCidr:0x000076df199fe240
 + @ipaddr=#<IPAddr: IPv4:10.0.11.35/255.255.255.255>>

What tests have you run against this PR?

• All existing IpAddrOrCidr unit specs pass (spec/unit/bosh/director/ip_addr_or_cidr_spec.rb)
• All existing IpRepo unit specs pass, including the CIDR block tests added by Fix IP Allocation Bug: Reserved Range Not Detected #2657 (spec/unit/bosh/director/deployment_plan/ip_provider/ip_repo_spec.rb)
• New unit tests added for #eql? and #hash covering:
  • Same base address + same prefix: eql? true, equal hashes, deduplicates in Set
  • Same base address + different prefix: eql? false, different hashes, coexist as distinct Set elements
  • Different base address: eql? false
  • Hash contract explicitly verified

How should this change be described in bosh release notes?

Fixed: IP allocation could intermittently assign addresses from reserved CIDR ranges due to non-deterministic Set behaviour in the IP dedup logic.

Does this PR introduce a breaking change?

No. This is a bug fix. The observable behaviour - that IPs are not allocated from reserved ranges — is unchanged; the fix makes it deterministic.

[coderabbitai]

Walkthrough

The changes modify how IP addresses and CIDR blocks are compared and hashed in the IP allocation system. The IpAddrOrCidr class is updated to use structural equality based on both the IP address integer and CIDR prefix, rather than object identity. The corresponding hash function is also updated to reflect this multi-key comparison. Additionally, the sorting behavior in ip_repo.rb is updated to use the same two-key ordering when determining candidate blocking IPs, and comprehensive tests are added to verify the new equality and hashing semantics.

Suggested reviewers

• fmoehler
• s4heid
• rkoster

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Fix flaky IP assignment' is concise and directly related to the main change—addressing non-deterministic behavior in IP allocation. It captures the primary objective without unnecessary detail.
Description check	✅ Passed	The PR description comprehensively covers all required template sections: what the change is about with specific changes listed, contextual information with links and CI failure logs, comprehensive test results, clear release notes guidance, and explicit breaking change assessment. All sections are well-populated and relevant.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix_flaky_ip_assignment

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/bosh-director/lib/bosh/director/ip_addr_or_cidr.rb`:
- Around line 47-51: The equality and hash implementations in IpAddrOrCidr
ignore address family causing IPv4 and IPv6 addresses with the same
integer/prefix to collide; update the eql? method (the equality check that
currently compares `@ipaddr.to_i` and `@ipaddr.prefix`) to also compare the address
family (e.g., `@ipaddr.family` or using ipv4?/ipv6?) and change the hash method to
include the same family value (e.g., include `@ipaddr.family` in the array used to
compute the hash) so that family is part of both equality and hashing.

🪄 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: ASSERTIVE

Plan: Pro

Run ID: 0554b280-a5ef-4ddc-8135-62fbc2037f04

📥 Commits

Reviewing files that changed from the base of the PR and between ef36ef9 and 5041f8d.

📒 Files selected for processing (3)

• src/bosh-director/lib/bosh/director/deployment_plan/ip_provider/ip_repo.rb
• src/bosh-director/lib/bosh/director/ip_addr_or_cidr.rb
• src/bosh-director/spec/unit/bosh/director/ip_addr_or_cidr_spec.rb