internal IEnumerable <ManagedDnsCacheEntry> GetDnsCacheEntries()
{
var ret = new List <ManagedDnsCacheEntry>();
var ptr = IntPtr.Zero;
var table = IntPtr.Zero;
if (_dnsGetCacheDataTable.Invoke(out table))
{
ptr = table;
do
{
var entry = (DnsCacheEntry)Marshal.PtrToStructure(ptr, typeof(DnsCacheEntry));
var domainName = Marshal.PtrToStringAuto(entry.pszName);
ret.AddRange(ExtractDnsARecords(domainName));
ret.AddRange(ExtractDnsAAAARecords(domainName));
var temp = ptr;
ptr = entry.pNext;
Win32Interop.DnsFree(entry.pszName, DnsFreeType.FreeFlat);
Win32Interop.DnsFree(temp, DnsFreeType.FreeFlat);
}while (ptr != IntPtr.Zero);
}
return(ret);
}
public void Dispose()
{
if (_dnsapiLibHandle != IntPtr.Zero)
{
if (!Win32Interop.FreeLibrary(_dnsapiLibHandle))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
}
internal DnsCacheHelper()
{
_dnsapiLibHandle = Win32Interop.LoadLibrary(@"dnsapi.dll");
if (_dnsapiLibHandle == IntPtr.Zero)
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
var procAddress = Win32Interop.GetProcAddress(_dnsapiLibHandle, nameof(Win32Interop.DnsGetCacheDataTable));
_dnsGetCacheDataTable = (Win32Interop.DnsGetCacheDataTable)Marshal.GetDelegateForFunctionPointer(procAddress, typeof(Win32Interop.DnsGetCacheDataTable));
}
private IEnumerable <ManagedDnsCacheEntry> ExtractDnsARecords(string domain)
{
var resultPtr = IntPtr.Zero;
var ret = new List <ManagedDnsCacheEntry>();
if (Win32Interop.DnsQuery(ref domain, DnsRecordType.A, (DnsQueryType)0x8010, IntPtr.Zero, ref resultPtr, IntPtr.Zero) == 0)
{
var recordIndexPtr = resultPtr;
do
{
var record = (DnsRecord)Marshal.PtrToStructure(recordIndexPtr, typeof(DnsRecord));
if (record.RecordType == DnsRecordType.A)
{
int size = Marshal.SizeOf(record);
recordIndexPtr += size;
var ipv4 = (DnsARecord)Marshal.PtrToStructure(recordIndexPtr, typeof(DnsARecord));
ret.Add(new ManagedDnsCacheEntry {
DomainName = domain, Address = new IPAddress(ipv4.IpAddress)
});
recordIndexPtr = record.Next;
}
else
{
recordIndexPtr = IntPtr.Zero;
}
} while (recordIndexPtr != IntPtr.Zero);
if (resultPtr != IntPtr.Zero)
{
Win32Interop.DnsFree(resultPtr, DnsFreeType.FreeRecordList);
}
}
return(ret);
}