Make Record.RR() always deterministic#190
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mholt merged 1 commit intolibdns:masterfrom Sep 2, 2025
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`SvcParams.String()` used to iterate over keys in a random order, which meant that calling `ServiceBinding.RR()` could return different `Data` for identical records. This commit sorts the keys in lexicographic order, making the result deterministic. Furthermore, since it seems useful for code to assume that it can safely roundtrip between `Record.RR()` and `RR.Parse()` and that `Record.RR()` is deterministic, I've now documented this. These are both already the case, but a formal guarantee should make external usage easier. Related to libdns#189.
mholt
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Sep 2, 2025
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SvcParams.String()used to iterate over keys in a random order, which meant that callingServiceBinding.RR()could return differentDatafor identical records. This commit sorts the keys in lexicographic order, making the result deterministic.Furthermore, since it seems useful for code to assume that it can safely roundtrip between
Record.RR()andRR.Parse()and thatRecord.RR()is deterministic, I've now documented this. These are both already the case, but a formal guarantee should make external usage easier.Related to #189.
RFC 9460 §2.1 says that we're allowed to place the keys in any order that we want, so I decided to sort the keys lexicographically since that was the easiest to implement. However, the canonical order is to sort by the key index, but this would require for us to hardcode the key↔index mapping.