TechnitiumSoftware/DnsServer · error · InvalidDataException

Failed to load DNS zone file: the zone file does not contain

Error message

Failed to load DNS zone file: the zone file does not contain any records.

What it means

Thrown by AuthZoneManager.LoadZoneFrom in zone-file version 4 (the current format, which serializes AuthZoneInfo and per-record auth info) when the record count read from the stream is less than 1. Version 4 stores the zone info separately and then the record array, so a zero record array is rejected immediately before parsing.

Source

Thrown at DnsServerCore/Dns/ZoneManagers/AuthZoneManager.cs:548

                        return zoneInfo;
                    }

                case 4:
                    {
                        //read zone info
                        AuthZoneInfo zoneInfo = new AuthZoneInfo(bR, lastModified);

                        //create zone
                        ApexZone apexZone = CreateEmptyApexZone(zoneInfo);
                        zoneInfo = new AuthZoneInfo(apexZone);

                        try
                        {
                            //read all zone records
                            DnsResourceRecord[] records = new DnsResourceRecord[bR.ReadInt32()];
                            if (records.Length < 1)
                                throw new InvalidDataException("Failed to load DNS zone file: the zone file does not contain any records.");

                            for (int i = 0; i < records.Length; i++)
                            {
                                records[i] = new DnsResourceRecord(s);
                                records[i].Tag = AuthRecordInfo.ReadGenericRecordInfoFrom(bR, records[i].Type);
                            }

                            //load and init zone
                            LoadAndInitZone(zoneInfo, records);
                        }
                        catch
                        {
                            DeleteZone(zoneInfo);
                            throw;
                        }

                        return zoneInfo;
                    }

View on GitHub (pinned to d0484b6c1e)

Solutions

Restore from backup or re-create/re-transfer the zone.
Make the writer refuse to persist a zone with zero records, and write atomically (temp + rename).
Validate the record count before invoking LoadZoneFrom.

Defensive patterns

Strategy: validation

Validate before calling

bool ZoneV4HasRecords(string path)
{
    using var fs = File.OpenRead(path);
    using var br = new BinaryReader(fs);
    if (Encoding.ASCII.GetString(br.ReadBytes(2)) != "DZ") return false;
    if (br.ReadByte() != 4) return false;
    // AuthZoneInfo header length is variable; this check is best done after a full header parse
    return true;
}

Try / catch

try { zoneManager.LoadZoneFrom(fs, lastModified); }
catch (InvalidDataException ex) when (ex.Message.Contains("does not contain any records"))
{
    // v4 zero records — restore backup or re-create/re-transfer
}

Prevention

Refuse to persist a zone with zero records.
Write zone files atomically (temp + rename).
Keep backups and validate record counts before loading.

When it happens

Trigger: Loading a version-4 zone file whose record-count integer is 0 — empty record list following a valid AuthZoneInfo header.

Common situations: A zone saved before any records existed, a truncated/partial write of the record section, or a corrupt count field.

Related errors

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/42e0be8b4bcd4fba. Report an issue: GitHub.