[GH-ISSUE #74] Panic on reenabling previously invalid zone #346

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opened 2026-03-13 14:43:25 +03:00 by kerem · 1 comment

kerem commented

2026-03-13 14:43:25 +03:00

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Originally created by @abligh on GitHub (Aug 19, 2015).
Original GitHub issue: https://github.com/abh/geodns/issues/74

This crash is similar to #69 but with a different cause (and different fix)

To replicate:

Alter dns/example.com so it is invalid (e.g. put an x at the top)
Start geodns
Alter dns/example.com so it is valid (e.g. remove the inserted x)
Wait for geodns to reload example.com
Perform any dig query for that zone e.g. to dig A weight.example.com @....

This produces a panic at:

    z.Metrics.Queries.Mark(1)

on line 34 of zone.go, because z.Metrics is {nil, nil, nil, nil}.

This cause of this problem is that when the zone is first loaded, Metrics is initialised to {nil, nil, nil, nil}. SetupMetrics is never called because the zone is invalid, but the old zone is kept around (presumably because in more complex circumstances it could have useful metrics in which should not be zeroed. When the zone is made loadable, old is non-nil, so the previous Metrics struct is copied, but not initialised, so it remains nil. The fix (coming right up) is to initialise any nil members of the Metrics struct whatever the value of old on entry.

Patch coming right up.

Originally created by @abligh on GitHub (Aug 19, 2015). Original GitHub issue: https://github.com/abh/geodns/issues/74 This crash is similar to #69 but with a different cause (and different fix) To replicate: - Alter `dns/example.com` so it is invalid (e.g. put an `x` at the top) - Start `geodns` - Alter `dns/example.com` so it is valid (e.g. remove the inserted `x`) - Wait for `geodns` to reload `example.com` - Perform any `dig` query for that zone e.g. to `dig A weight.example.com @....` This produces a panic at: ``` z.Metrics.Queries.Mark(1) ``` on line 34 of `zone.go`, because z.Metrics is `{nil, nil, nil, nil}`. This cause of this problem is that when the zone is first loaded, `Metrics` is initialised to `{nil, nil, nil, nil}`. `SetupMetrics` is never called because the zone is invalid, but the old zone is kept around (presumably because in more complex circumstances it could have useful metrics in which should not be zeroed. When the zone is made loadable, `old` is non-nil, so the previous `Metrics` `struct` is copied, but not initialised, so it remains `nil`. The fix (coming right up) is to initialise any `nil` members of the `Metrics` struct whatever the value of `old` on entry. Patch coming right up.