BornToBeRoot/NETworkManager · error · Win32Exception

Win32Exception for native error code (int)result

Error message

Win32Exception for native error code (int)result

What it means

GetTable calls the native GetIpNetTable2 (ARP/neighbor table) and, when it returns a non-zero HRESULT/error code, throws new Win32Exception((int)result). The Win32Exception message is derived from the native code (e.g. ERROR_NO_DATA = 'Element not found' when the neighbor table is empty, ERROR_NOT_ENOUGH_MEMORY, or access errors).

Solutions

  1. Treat error 1168 (ERROR_NO_DATA / empty table) as an empty result instead of an exception.
  2. Catch Win32Exception and check NativeErrorCode before surfacing the error to the UI.
  3. Retry after a short delay if the interface was just enabled.
  4. Run with sufficient privileges; verify the machine has at least one active IPv4/IPv6 interface.

Example fix

// before
var result = GetIpNetTable2(AF_UNSPEC, out table);
if (result != 0)
    throw new Win32Exception((int)result);
// after
var result = GetIpNetTable2(AF_UNSPEC, out table);
if (result == 1168) // ERROR_NO_DATA: empty neighbor table
    return Enumerable.Empty<MIB_IPNET_ROW2>();
if (result != 0)
    throw new Win32Exception((int)result);
Defensive patterns

Strategy: try-catch

Validate before calling

null

Try / catch

try
{
    var entries = NeighborTable.GetTable();
}
catch (Win32Exception ex) when (ex.NativeErrorCode == 1168)
{
    // empty ARP table - not an error
    var entries = Enumerable.Empty<NeighborTableEntryInfo>();
}
catch (Win32Exception ex)
{
    Log.Warn($"GetIpNetTable2 failed: {ex.NativeErrorCode} {ex.Message}");
    throw;
}

Prevention

When it happens

Trigger: Calling GetTable (via the public entry that enumerates neighbor entries) on a system/interface with no ARP entries (ERROR_NO_DATA, code 1168), when the API is unavailable, or on allocation failure.

Common situations: Querying immediately after an interface comes up with an empty neighbor cache; running in restricted environments (services with limited access to network stack APIs); older Windows versions without GetIpNetTable2 behavior expectations.

Related errors

AI-assisted analysis of BornToBeRoot/NETworkManager@2780d65469 (2026-09-12). Data as JSON: /api/errors/c29cb43bbfaf39f1. Report an issue: GitHub.

Appendix: source

Thrown at Source/NETworkManager.Models/Network/NeighborTable.cs:161

    /// are suppressed.
    /// </summary>
    private static List<NeighborInfo> GetTable()
    {
        var list = new List<NeighborInfo>();

        var virtualMAC = new PhysicalAddress([0, 0, 0, 0, 0, 0]);
        var broadcastMAC = new PhysicalAddress([255, 255, 255, 255, 255, 255]);

        var aliasMap = GetCachedInterfaceAliasMap();

        var table = IntPtr.Zero;

        try
        {
            var result = GetIpNetTable2(AF_UNSPEC, out table);

            if (result != 0)
                throw new Win32Exception((int)result);

            // First 4 bytes hold NumEntries; the array of MIB_IPNET_ROW2 starts after
            // 4 bytes of padding (the row contains a ULONG64, requiring 8-byte alignment).
            var numEntries = Marshal.ReadInt32(table);
            var rowSize = Marshal.SizeOf<MIB_IPNET_ROW2>();
            var arrayPtr = IntPtr.Add(table, 8);

            for (var i = 0; i < numEntries; i++)
            {
                var row = Marshal.PtrToStructure<MIB_IPNET_ROW2>(IntPtr.Add(arrayPtr, i * rowSize));

                var family = BitConverter.ToUInt16(row.Address, 0);

                IPAddress ipAddress;
                AddressFamily addressFamily;

                switch (family)
                {

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