Implement DnsResolver for Windows

src/libraries/Common/src/Interop/Windows/Dnsapi/Interop.DnsApi.cs

@@ -0,0 +1,68 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Dnsapi
+    {
+        // ---- Query types we use ----
+        internal const ushort DNS_TYPE_A = 0x0001;
+        internal const ushort DNS_TYPE_NS = 0x0002;
+        internal const ushort DNS_TYPE_CNAME = 0x0005;
+        internal const ushort DNS_TYPE_SOA = 0x0006;
+        internal const ushort DNS_TYPE_PTR = 0x000c;
+        internal const ushort DNS_TYPE_MX = 0x000f;
+        internal const ushort DNS_TYPE_TEXT = 0x0010;
+        internal const ushort DNS_TYPE_AAAA = 0x001c;
+        internal const ushort DNS_TYPE_SRV = 0x0021;
+
+        // ---- DnsQueryEx return codes / Win32 error codes ----
+        internal const int DNS_REQUEST_PENDING = 9506;
+        internal const int ERROR_SUCCESS = 0;
+        internal const int DNS_INFO_NO_RECORDS = 9501;
+        internal const int DNS_ERROR_RCODE_FORMAT_ERROR = 9001;
+        internal const int DNS_ERROR_RCODE_SERVER_FAILURE = 9002;
+        internal const int DNS_ERROR_RCODE_NAME_ERROR = 9003;
+        internal const int DNS_ERROR_RCODE_NOT_IMPLEMENTED = 9004;
+        internal const int DNS_ERROR_RCODE_REFUSED = 9005;
+
+        // ---- DnsQueryEx options ----
+        internal const ulong DNS_QUERY_STANDARD = 0x00000000;
+        internal const ulong DNS_QUERY_RETURN_MESSAGE = 0x00020000;
+
+        // ---- Query request versions ----
+        internal const uint DNS_QUERY_REQUEST_VERSION1 = 0x1;
+        internal const uint DNS_QUERY_REQUEST_VERSION3 = 0x3;
+
+        // ---- DNS_ADDR address family marker — addresses are stored in SOCKADDR form ----
+        internal const ushort AF_INET = 2;
+        internal const ushort AF_INET6 = 23;
+
+        // ---- DNS_CUSTOM_SERVER server types ----
+        internal const uint DNS_CUSTOM_SERVER_TYPE_UDP = 0x1;
+        internal const uint DNS_CUSTOM_SERVER_TYPE_DOH = 0x2;
+
+        // ---- DNS_CUSTOM_SERVER usage flags ----
+        internal const ulong DNS_CUSTOM_SERVER_UDP_FALLBACK = 0x1;
+
+        // ---- DnsFreeType for DnsFree ----
+        internal const int DnsFreeFlat = 0;
+        internal const int DnsFreeRecordList = 1;
+        internal const int DnsFreeParsedMessageFields = 2;
+
+        [LibraryImport(Libraries.Dnsapi, EntryPoint = "DnsQueryEx")]
+        internal static unsafe partial int DnsQueryEx(
+            DNS_QUERY_REQUEST* pQueryRequest,
+            DNS_QUERY_RESULT* pQueryResults,
+            DNS_QUERY_CANCEL* pCancelHandle);
+
+        [LibraryImport(Libraries.Dnsapi, EntryPoint = "DnsCancelQuery")]
+        internal static unsafe partial int DnsCancelQuery(DNS_QUERY_CANCEL* pCancelHandle);
+
+        [LibraryImport(Libraries.Dnsapi, EntryPoint = "DnsFree")]
+        internal static partial void DnsFree(IntPtr pData, int freeType);
+    }
+}

src/libraries/Common/src/Interop/Windows/Dnsapi/Interop.DnsTypes.cs

@@ -0,0 +1,199 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class Dnsapi
+    {
+        // DNS_QUERY_REQUEST (v1) — Win8 / Server 2012+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_QUERY_REQUEST
+        {
+            public uint Version;
+            public char* QueryName;    // PCWSTR
+            public ushort QueryType;
+            public ulong QueryOptions;
+            public DNS_ADDR_ARRAY* pDnsServerList;
+            public uint InterfaceIndex;
+            public delegate* unmanaged[Stdcall]<nint, nint, void> pQueryCompletionCallback; // PDNS_QUERY_COMPLETION_ROUTINE
+            public IntPtr pQueryContext;
+        }
+
+        // DNS_QUERY_REQUEST3 — Win11 Build 22000+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_QUERY_REQUEST3
+        {
+            public uint Version;
+            public char* QueryName;
+            public ushort QueryType;
+            public ulong QueryOptions;
+            public DNS_ADDR_ARRAY* pDnsServerList;
+            public uint InterfaceIndex;
+            public delegate* unmanaged[Stdcall]<nint, nint, void> pQueryCompletionCallback;
+            public IntPtr pQueryContext;
+            public int IsNetworkQueryRequired;   // BOOL
+            public uint RequiredNetworkIndex;
+            public uint cCustomServers;
+            public DNS_CUSTOM_SERVER* pCustomServers;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_QUERY_RESULT
+        {
+            public uint Version;
+            public int QueryStatus;
+            public ulong QueryOptions;
+            public IntPtr pQueryRecords;     // DNS_RECORD*
+            public IntPtr Reserved;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_QUERY_CANCEL
+        {
+            public fixed byte Reserved[32];
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_ADDR
+        {
+            // SOCKET_ADDRESS-like: 32 bytes of SOCKADDR_STORAGE-ish + extras.
+            // DnsApi documents this struct as 64 bytes total with the first 32
+            // being the SOCKADDR (IPv4/IPv6 SOCKADDR fits within).
+            public fixed byte MaxSa[32];
+            public uint DnsAddrUserDword0;
+            public uint DnsAddrUserDword1;
+            public uint DnsAddrUserDword2;
+            public uint DnsAddrUserDword3;
+            public uint DnsAddrUserDword4;
+            public uint DnsAddrUserDword5;
+            public uint DnsAddrUserDword6;
+            public uint DnsAddrUserDword7;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_ADDR_ARRAY
+        {
+            public uint MaxCount;
+            public uint AddrCount;
+            public uint Tag;
+            public ushort Family;
+            public ushort WordReserved;
+            public uint Flags;
+            public uint MatchFlag;
+            public uint Reserved1;
+            public uint Reserved2;
+            // followed by AddrCount entries of DNS_ADDR
+            // (we allocate the trailing array contiguously)
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_CUSTOM_SERVER
+        {
+            public uint dwServerType;       // DNS_CUSTOM_SERVER_TYPE_*
+            public ulong ullFlags;
+            public char* pwszTemplate;      // PCWSTR (DoH only)
+            public fixed byte ServerAddr[32]; // SOCKADDR
+        }
+
+        // ---- DNS_RECORD (variable layout: header + Data union) ----
+        // We declare the fixed header layout and read the data area as a byte blob,
+        // re-interpreting per record type. The Data union follows the header; because the
+        // header contains two pointers, its size (and therefore the Data offset) depends on
+        // the pointer width - 24 bytes on 32-bit and 32 bytes on 64-bit. Callers must use
+        // sizeof(DNS_RECORD_HEADER) rather than a hard-coded offset.
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_RECORD_HEADER
+        {
+            public IntPtr pNext;        // DNS_RECORD*
+            public char* pName;         // PCWSTR
+            public ushort wType;
+            public ushort wDataLength;  // not always reliable; use type to interpret
+            public uint Flags;          // contains Section in the low bits
+            public uint dwTtl;
+            public uint dwReserved;
+            // followed by Data union
+        }
+
+        // ---- Section field within DNS_RECORD.Flags ----
+        // The Section is the lowest 2 bits of the DW_FLAGS field.
+        internal const uint DNSREC_SECTION_MASK = 0x3;
+        internal const uint DNSREC_QUESTION = 0;
+        internal const uint DNSREC_ANSWER = 1;
+        internal const uint DNSREC_AUTHORITY = 2;
+        internal const uint DNSREC_ADDITIONAL = 3;
+
+        // ---- Data unions ----
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct DNS_A_DATA
+        {
+            public uint IpAddress; // network byte order
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct DNS_AAAA_DATA
+        {
+            public InlineArray16<byte> Ip6Address;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_PTR_DATA
+        {
+            public char* pNameHost; // PCWSTR
+        }
+
+        // Same shape as DNS_PTR_DATA — Windows uses DNS_PTR_DATA for NS/CNAME too,
+        // but typed aliases keep call sites self-documenting.
+#pragma warning disable CS0649 // fields populated via native marshalling
+        internal unsafe struct DNS_CNAME_DATA
+        {
+            public char* pNameHost;
+        }
+
+        internal unsafe struct DNS_NS_DATA
+        {
+            public char* pNameHost;
+        }
+#pragma warning restore CS0649
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_MX_DATA
+        {
+            public char* pNameExchange; // PCWSTR
+            public ushort wPreference;
+            public ushort Pad;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_SRV_DATA
+        {
+            public char* pNameTarget; // PCWSTR
+            public ushort wPriority;
+            public ushort wWeight;
+            public ushort wPort;
+            public ushort Pad;
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_TXT_DATA
+        {
+            public uint dwStringCount;
+            // followed by dwStringCount entries of PCWSTR
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal unsafe struct DNS_SOA_DATA
+        {
+            public char* pNamePrimaryServer;    // PCWSTR
+            public char* pNameAdministrator;    // PCWSTR
+            public uint dwSerialNo;
+            public uint dwRefresh;
+            public uint dwRetry;
+            public uint dwExpire;
+            public uint dwDefaultTtl;
+        }
+    }
+}

src/libraries/Common/src/Interop/Windows/Interop.Libraries.cs

@@ -12,6 +12,7 @@ internal static partial class Libraries
         internal const string Credui = "credui.dll";
         internal const string Crypt32 = "crypt32.dll";
         internal const string CryptUI = "cryptui.dll";
+        internal const string Dnsapi = "dnsapi.dll";
         internal const string Dsrole = "dsrole.dll";
         internal const string Gdi32 = "gdi32.dll";
         internal const string HttpApi = "httpapi.dll";