virttest: Fix UnboundLocalError in restart_guest_network()

[BulaYoungR]

Fix a bug in restart_guest_network() where restart_cmd variable was used before initialization when mac_addr parameter is None.

Error occurred at line 1761:
restart_cmd += "%s %s; " % (dhcp_cmd, release_flag)

The += operator attempted to append to restart_cmd, but the variable was never initialized in the else branch (when mac_addr is None).

The variable restart_cmd is only initialized in the if mac_addr block (line 1754), so when execution reaches the else block, restart_cmd does not exist, causing:
UnboundLocalError: local variable 'restart_cmd' referenced before assignment

Fix: Change line 1761 from += to = to properly initialize the variable:
restart_cmd = "%s %s; " % (dhcp_cmd, release_flag)

Committer: Bolatbek Issakh bissakh@redhat.com

[gemini-code-assist]

Summary of Changes

Hello @BulaYoungR, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical runtime error in the network utility function restart_guest_network(). The fix ensures that a command string variable is properly initialized under all execution paths, preventing an UnboundLocalError and improving the robustness of guest network restart operations.

Highlights

• Bug Fix: Addressed an UnboundLocalError in the restart_guest_network() function that occurred when the mac_addr parameter was None.
• Initialization Logic: Corrected the initialization of the restart_cmd variable by changing an additive assignment (+=) to a direct assignment (=) in the else branch, ensuring the variable is always defined before use.

Changelog

• virttest/utils_net.py
  • Fixed an UnboundLocalError by ensuring the 'restart_cmd' variable is correctly initialized in all code paths.

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[BulaYoungR]

Before fix

(.libvirt-ci-venv-ci-runtest-Ts1Wmd) [root@ampere-mtsnow-altramax-12 libvirt-ci-latest-venv]# bin/avocado run --vt-type libvirt --vt-omit-data-loss --vt-machine-type arm64-mmio virtual_network.iface_bridge.default.shared_physical_network --job-timeout 1200 --vt-connect-uri qemu:///system
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
JOB ID     : f55cff5401c26e8dfd9d3b2ea16423cf2a7fe5d2
JOB LOG    : /var/log/avocado/job-results/job-2026-02-11T09.52-f55cff5/job.log
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.iface_bridge.default.shared_physical_network: STARTED
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.iface_bridge.default.shared_physical_network: ERROR: local variable 'restart_cmd' referenced before assignment (62.23 s)
RESULTS    : PASS 0 | ERROR 1 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML   : /var/log/avocado/job-results/job-2026-02-11T09.52-f55cff5/results.html
JOB TIME   : 63.62 s

After fix

(.libvirt-ci-venv-ci-runtest-Ts1Wmd) [root@ampere-mtsnow-altramax-12 libvirt-ci-latest-venv]# bin/avocado run --vt-type libvirt --vt-omit-data-loss --vt-machine-type arm64-mmio virtual_network.iface_bridge.default.shared_physical_network --job-timeout 1200 --vt-connect-uri qemu:///system
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
JOB ID     : 80157eeb5be4c600ca25161f53e4bf2b3b2173af
JOB LOG    : /var/log/avocado/job-results/job-2026-02-11T09.56-80157ee/job.log
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.iface_bridge.default.shared_physical_network: STARTED
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.iface_bridge.default.shared_physical_network: PASS (141.00 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML   : /var/log/avocado/job-results/job-2026-02-11T09.56-80157ee/results.html
JOB TIME   : 142.57 s

[gemini-code-assist]

Code Review

This pull request addresses an UnboundLocalError in restart_guest_network() by correctly initializing the restart_cmd variable. The error occurred when mac_addr was None, as the variable was used with += before being assigned a value. The fix, changing += to =, is correct and effectively resolves the bug. The change is approved.