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Fix External-DHCP APIPA/Link-local address on L2 networks by nvazquez · Pull Request #14333 · apache/cloudstack · GitHub
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Fix External-DHCP APIPA/Link-local address on L2 networks - #14333

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shapeblue:l2-external-dchp-ip-fix
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Fix External-DHCP APIPA/Link-local address on L2 networks#14333
nvazquez wants to merge 1 commit into
apache:4.22from
shapeblue:l2-external-dchp-ip-fix

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@nvazquez

@nvazquez nvazquez commented Oct 7, 2026

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Description

This PR an issue observed on L2 Networks with external DHCP server:

On an L2 guest network with an external DHCP server, CloudStack learns a Windows VM's IP address as the self-assigned (APIPA / link-local) address 169.254.149.120. It recorded that as the NIC's IP and never refreshed it. More than 30 minutes later, listVirtualMachines still reports 169.254.149.120, while the guest really has 172.25.16.236 (DHCP). The QEMU guest agent reports 172.25.16.236, and SSH on 172.25.16.236:22 is reachable.

Types of changes

  • Breaking change (fix or feature that would cause existing functionality to change)
  • New feature (non-breaking change which adds functionality)
  • Bug fix (non-breaking change which fixes an issue)
  • Enhancement (improves an existing feature and functionality)
  • Cleanup (Code refactoring and cleanup, that may add test cases)
  • Build/CI
  • Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

  • Major
  • Minor

Bug Severity

  • BLOCKER
  • Critical
  • Major
  • Minor
  • Trivial

Screenshots (if appropriate):

How Has This Been Tested?

How did you try to break this feature and the system with this change?

@nvazquez nvazquez added this to the 4.22.2 milestone Oct 7, 2026
@nvazquez

nvazquez commented Oct 7, 2026

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@blueorangutan package

@blueorangutan

blueorangutan commented Oct 7, 2026

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@nvazquez a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

@codecov

codecov Bot commented Oct 7, 2026 •
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Codecov Report

❌ Patch coverage is 66.66667% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 18.02%. Comparing base (2974af8) to head (3c97325).

Files with missing lines Patch % Lines
.../src/main/java/com/cloud/vm/UserVmManagerImpl.java 0.00% 7 Missing ⚠️
...ls/src/main/java/com/cloud/utils/net/NetUtils.java 85.71% 2 Missing ⚠️
Additional details and impacted files 
@@             Coverage Diff              @@
##               4.22   #14333      +/-   ##
============================================
- Coverage     18.02%   18.02%   -0.01%     
- Complexity    16250    16262      +12     
============================================
  Files          5936     5936              
  Lines        535823   535847      +24     
  Branches      65612    65617       +5     
============================================
+ Hits          96582    96586       +4     
- Misses       428242   428263      +21     
+ Partials      10999    10998       -1
Flag Coverage Δ
uitests 4.04% <ø> (ø)
unittests 19.09% <66.66%> (-0.01%) ⬇️

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weizhouapache
weizhouapache approved these changes Oct 7, 2026
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code lgtm

@blueorangutan

blueorangutan commented Oct 7, 2026

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Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 19442

@nvazquez

nvazquez commented Oct 7, 2026

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@blueorangutan test

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blueorangutan commented Oct 7, 2026

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@nvazquez a [SL] Trillian-Jenkins test job (ol8 mgmt + kvm-ol8) has been kicked to run smoke tests

@nvazquez
nvazquez requested a balanced review from Copilot October 7, 2026 14:25
Copilot AI reviewed Oct 7, 2026
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Copilot review overview

🟡 Changes recommended

Legacy APIPA values can remain exposed, and malformed IPv6 zone input can throw unexpectedly.

Review effort: Balanced
Findings: 2 Medium severity

Open (2)
What changed in this PR

Fixes stale APIPA/link-local addresses reported for externally DHCP-managed L2 VM NICs.

Changes:

  • Adds IPv4/IPv6 link-local detection utilities.
  • Filters link-local addresses from KVM guest-agent results.
  • Retries NICs containing previously recorded APIPA addresses.
File Description
NetUtils.java Adds link-local address helpers.
NetUtilsTest.java Tests link-local detection.
UserVmManagerImpl.java Handles and retries APIPA NIC addresses.
LibvirtGetVmIpAddressCommandWrapper.java Ignores link-local guest addresses.
LibvirtGetVmIpAddressCommandWrapperTest.java Tests APIPA and DHCP parsing.

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Comment thread server/src/main/java/com/cloud/vm/UserVmManagerImpl.java
for (NicVO nic : nics) {
if (nic.getIPv4Address() == null) {
// also retry NICs holding a link-local (APIPA) address recorded before the guest obtained its DHCP lease
if (nic.getIPv4Address() == null || NetUtils.isLinkLocalIp4(nic.getIPv4Address())) {
Comment thread utils/src/main/java/com/cloud/utils/net/NetUtils.java
if (ip == null) {
return false;
}
final String address = ip.split("%")[0];
@blueorangutan

blueorangutan commented Oct 8, 2026

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[SF] Trillian test result (tid-17089)
Environment: kvm-ol8 (x2), zone: Advanced Networking with Mgmt server ol8
Total time taken: 49968 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr14333-t17089-kvm-ol8.zip
Smoke tests completed. 149 look OK, 0 have errors, 0 did not run
Only failed and skipped tests results shown below:

Test Result Time (s) Test File

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@weizhouapache weizhouapache weizhouapache approved these changes
@shwstppr shwstppr Awaiting requested review from shwstppr
@kiranchavala kiranchavala Awaiting requested review from kiranchavala
@NuxRo NuxRo Awaiting requested review from NuxRo
@Pearl1594 Pearl1594 Awaiting requested review from Pearl1594
@vladimirpetrov vladimirpetrov Awaiting requested review from vladimirpetrov
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component:kvm component:networking type:bug

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4.22.2

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4 participants

@nvazquez @blueorangutan @weizhouapache