nixos/sshguard: create ipsets before starting, and clean up after stopping. #65995
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…pping. The fix for #62874 introduced a race condition on startup: the postStart commands that configure the firewall run concurrently with sshguard's creation of the ipsets that the rules depend on. Unfortunately iptables fails hard when referencing an ipset that doesn't exist, so this causes non-deterministic crashlooping until sshguard wins the race. This change fixes that race condition by always creating the ipset and reconfiguring the firewall before starting sshguard, so that the order of operations is always deterministic. This change also cleans up the ipsets on sshguard shutdown, so that removing sshguard from a running system doesn't leave state behind. Fixes #65985.
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This should also be backported to 19.03 ideally, because right now sshguard sometimes fails to start (if the race condition hits too many times, systemd stops retrying). |
ofborg
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6.topic: nixos
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Thank you for it, I've tested it in a new VM, looks legit. Do you mind cherry picking this to 19.03? |
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@danderson --- Sorry about the bug, and thank you for fixing. |
Janik-Haag
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The fix for #62874 introduced a race condition on startup: the postStart
commands that configure the firewall run concurrently with sshguard's
creation of the ipsets that the rules depend on. Unfortunately iptables
fails hard when referencing an ipset that doesn't exist, so this causes
non-deterministic crashlooping until sshguard wins the race.
This change fixes that race condition by always creating the ipset and
reconfiguring the firewall before starting sshguard, so that the order
of operations is always deterministic.
This change also cleans up the ipsets on sshguard shutdown, so that
removing sshguard from a running system doesn't leave state behind.
Motivation for this change
Fixes #65985.
Things done
sandboxinnix.confon non-NixOS)nix-shell -p nix-review --run "nix-review wip"./result/bin/)nix path-info -Sbefore and after)Notify maintainers
cc @sargon