[DO NOT MERGE] Diagnostic test for QEMU s390x netlink issue#506
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[DO NOT MERGE] Diagnostic test for QEMU s390x netlink issue#506
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packit copr-build |
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COPR lost native s390x builders around March 2026 and switched to QEMU user-mode emulation on x86_64. QEMU doesn't properly byte-swap netlink RTM_GETLINK rtattr structs when emulating big-endian s390x on a little-endian host, causing Go's net.InterfaceByName() to fail with 'parsenetlinkrouteattr: invalid argument'. We confirmed this is a QEMU bug, not a code issue: - Native s390x (Koji): all tests pass - Native x86_64: all tests pass - QEMU s390x (COPR): only netlink RTM_GETLINK tests fail - Diagnostic test (PR #506) shows RTM_GETADDR works, RTM_GETLINK doesn't, sysfs/procfs alternatives work fine A patch has been submitted to QEMU upstream. Removing s390x from COPR targets until the QEMU fix lands. This only affects CI testing, not the official Fedora package. Koji still builds s390x with real hardware and Fedora users are unaffected.
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Summary: COPR lost native s390x builders around March 2026 and switched to QEMU user-mode emulation on x86_64. QEMU doesn't properly byte-swap netlink RTM_GETLINK rtattr structs when emulating big-endian s390x on a little-endian host, causing Go's net.InterfaceByName() to fail with 'parsenetlinkrouteattr: invalid argument'. We confirmed this is a QEMU bug, not a code issue: - Native s390x (Koji): all tests pass - Native x86_64: all tests pass - QEMU s390x (COPR): only netlink RTM_GETLINK tests fail - Diagnostic test (PR #506) shows RTM_GETADDR works, RTM_GETLINK doesn't, sysfs/procfs alternatives work fine A patch has been submitted to QEMU upstream. Removing s390x from COPR targets until the QEMU fix lands. This only affects CI testing, not the official Fedora package. Koji still builds s390x with real hardware and Fedora users are unaffected. https://gitlab.com/qemu-project/qemu/-/work_items/2485#note_3236597357 Pull Request resolved: #508 Reviewed By: vvfedorenko Differential Revision: D100185224 Pulled By: ESoapW fbshipit-source-id: 9070472bd76975b7dbb94de3514ffa300ba19f50
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Closing this PR. The diagnostic test served its purpose and we found the root cause. What we foundThe netdiag test helped us trace the issue to a one-character off-by-one bug in QEMU's Key evidence from the diagnostic
StatusThe bug has been in QEMU since 2016 (commit |
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DO NOT MERGE - diagnostic only
Adding a test package (netdiag/) to figure out exactly which network interface detection methods break under QEMU s390x emulation. We've been seeing parsenetlinkrouteattr: invalid argument on COPR s390x builds since they lost native builders around Mar 13.
This tests netlink, sysfs, procfs, and raw socket paths independently and prints a summary table. Expecting netlink methods to fail while sysfs/procfs alternatives work fine, which would confirm the issue is QEMU's incomplete byte-order translation of netlink rtattr structs.
Will close after reviewing COPR build logs.