microvm.nix interface creation logic is racey #289

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opened 2025-08-27 00:52:41 +00:00 by raito · 0 comments
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Upon very fast start of new microVMs with no assigned interfaces:

Aug 27 00:51:28 lix-hv01 microvm@lix-zulip01[2777864]: /var/lib/microvms/lix-zulip01/current/bin/microvm-run: line 53: /sys/class/net/vm-ff9b-wan/ifindex: No such file or directory
Aug 27 00:51:28 lix-hv01 microvm@lix-zulip01[2777864]: /var/lib/microvms/lix-zulip01/current/bin/microvm-run: line 53: /dev/tap: Permission denied

can happen.

This suggest a race in interface creation. It's unsurprising as microvm.nix is a pile of Bash in too many areas and should probably rely more on networkd or similar.

Upon very fast start of new microVMs with no assigned interfaces: ``` Aug 27 00:51:28 lix-hv01 microvm@lix-zulip01[2777864]: /var/lib/microvms/lix-zulip01/current/bin/microvm-run: line 53: /sys/class/net/vm-ff9b-wan/ifindex: No such file or directory Aug 27 00:51:28 lix-hv01 microvm@lix-zulip01[2777864]: /var/lib/microvms/lix-zulip01/current/bin/microvm-run: line 53: /dev/tap: Permission denied ``` can happen. This suggest a race in interface creation. It's unsurprising as microvm.nix is a pile of Bash in too many areas and should probably rely more on networkd or similar.
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Reference: the-distro/infra#289
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