Gary Sharp
318 lines
13 KiB
C#
318 lines
13 KiB
C#
using System;
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using System.Collections.Generic;
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using System.ComponentModel;
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using System.Linq;
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using System.Net;
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using System.Net.NetworkInformation;
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using System.Runtime.InteropServices;
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using System.Threading;
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namespace Disco.Client.Interop
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{
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internal class EndpointDiscovery
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{
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[DllImport("dnsapi", EntryPoint = "DnsQuery_W", CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
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private static extern int DnsQuery([MarshalAs(UnmanagedType.VBByRefStr)] ref string pszName, NativeDnsQueryTypes wType, NativeDnsQueryOptions options, int aipServers, ref IntPtr ppQueryResults, int pReserved);
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[DllImport("dnsapi", CharSet = CharSet.Auto, SetLastError = true)]
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private static extern void DnsRecordListFree(IntPtr pRecordList, int FreeType);
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private const int DNS_ERROR_RCODE_NAME_ERROR = 0x232B;
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private const int DNS_ERROR_BAD_PACKET = 0x251E;
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public static Tuple<Uri, string> DiscoverServer(Uri forcedServerUri)
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{
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// 1. Check first command line argument for server name
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if (forcedServerUri != null)
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return Tuple.Create(forcedServerUri, "Manual");
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// 2. Check for a DNS SRV record for _discoict._tcp.domain
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var domainSuffixes = new List<string>();
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var primaryDomain = IPGlobalProperties.GetIPGlobalProperties().DomainName;
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if (!string.IsNullOrEmpty(primaryDomain))
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domainSuffixes.Add(primaryDomain);
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var networkInterfaces = NetworkInterface.GetAllNetworkInterfaces()
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.Where(ni => ni.OperationalStatus == OperationalStatus.Up);
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foreach (var ni in networkInterfaces)
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{
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var domainSuffix = ni.GetIPProperties().DnsSuffix;
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if (!string.IsNullOrWhiteSpace(domainSuffix))
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{
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if (domainSuffix.Equals("mshome.net", StringComparison.OrdinalIgnoreCase))
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continue;
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if (!domainSuffixes.Contains(domainSuffix, StringComparer.OrdinalIgnoreCase))
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domainSuffixes.Add(domainSuffix);
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}
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}
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foreach (var domain in domainSuffixes)
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{
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var dnsRecords = GetSRVRecords("_discoict._tcp." + domain);
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if (dnsRecords.Count > 0)
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{
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var firstRecord = dnsRecords.OrderBy(r => r.Priority).ThenByDescending(r => r.Weight).First();
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if (firstRecord.Port == 443)
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return Tuple.Create(new Uri($"https://{firstRecord.Target}"), "SRV");
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else
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return Tuple.Create(new Uri($"https://{firstRecord.Target}:{firstRecord.Port}"), "SRV");
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}
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}
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// 3. Detect VicSmart network and try resolving with Disco ICT Online Services
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if (TryResolveVicSmartServer(domainSuffixes, out var vicSmartServerUrl))
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return Tuple.Create(vicSmartServerUrl, "VicSmart");
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// 4. Legacy: Ping 'disco' and assume port 9292
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using (Ping p = new Ping())
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{
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try
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{
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PingReply pr = p.Send("disco", 2000);
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if (pr.Status == IPStatus.Success)
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return Tuple.Create(new Uri("http://disco:9292"), "Legacy");
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}
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catch (Exception)
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{
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}
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}
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throw new Exception("Could not locate Disco ICT server on the network.");
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}
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private static bool TryResolveVicSmartServer(List<string> domainSuffixes, out Uri serverUrl)
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{
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if (IsVicSmartNetwork(domainSuffixes))
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{
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var potentialVicSmartAddresses = NetworkInterface.GetAllNetworkInterfaces()
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.Where(ni => ni.OperationalStatus == OperationalStatus.Up)
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.SelectMany(ni => ni.GetIPProperties().UnicastAddresses)
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.Where(ua => ua.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
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.Select(ua => ua.Address.GetAddressBytes())
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.Where(a => a[0] == 10)
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.Select(a => (ushort)((a[1] >> 4) & 0x000F) | ((a[1] << 4) & 0x00F0) | ((a[2] << 12) & 0xF000) | ((a[2] << 4) & 0x0F00))
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.Distinct()
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.Select(a => $"{a:x4}.vicsmart.discoict.com")
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.ToList();
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foreach (var potentialAddress in potentialVicSmartAddresses)
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{
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var records = GetTxtRecords(potentialAddress);
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foreach (var record in records)
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{
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if (!record.Content.StartsWith("https://", StringComparison.OrdinalIgnoreCase))
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continue;
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if (Uri.TryCreate(record.Content, UriKind.Absolute, out var discoveredUri))
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{
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serverUrl = discoveredUri;
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return true;
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}
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}
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}
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}
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serverUrl = null;
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return false;
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}
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private static bool IsVicSmartNetwork(List<string> domainSuffixes)
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{
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if (domainSuffixes.Any(s => string.Equals("services.education.vic.gov.au", s, StringComparison.OrdinalIgnoreCase)) ||
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domainSuffixes.Any(s => string.Equals("education.vic.gov.au", s, StringComparison.OrdinalIgnoreCase))
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)
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return true;
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IPHostEntry doeWanDnsEntry;
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try
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{
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doeWanDnsEntry = Dns.GetHostEntry("broadband.doe.wan");
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if (doeWanDnsEntry.AddressList.Length > 0)
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return true;
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}
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catch (Exception)
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{ }
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return false;
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}
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private static List<DnsTxtRecord> GetTxtRecords(string name)
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{
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IntPtr resourceRecordsPointer = IntPtr.Zero;
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var records = new List<DnsTxtRecord>();
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var retry = 5;
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retry:
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try
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{
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int queryResult = DnsQuery(ref name, NativeDnsQueryTypes.DNS_TYPE_TEXT, NativeDnsQueryOptions.DNS_QUERY_STANDARD, 0, ref resourceRecordsPointer, 0);
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if (queryResult != 0)
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{
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if (queryResult == DNS_ERROR_RCODE_NAME_ERROR)
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return records;
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else if (queryResult == DNS_ERROR_BAD_PACKET && retry > 0)
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{
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// Sometimes a BAD_PACKET error is returned, retry a few times
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Thread.Sleep(200);
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retry--;
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goto retry;
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}
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else
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throw new Win32Exception(queryResult);
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}
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NativeDnsTxtRecord record;
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for (var resourceRecordPointer = resourceRecordsPointer; !resourceRecordPointer.Equals(IntPtr.Zero); resourceRecordPointer = record.pNext)
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{
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record = Marshal.PtrToStructure<NativeDnsTxtRecord>(resourceRecordPointer);
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if (record.wType == (ushort)NativeDnsQueryTypes.DNS_TYPE_TEXT)
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records.Add(DnsTxtRecord.FromNativeRecord(record));
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}
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}
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finally
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{
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if (resourceRecordsPointer != IntPtr.Zero)
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DnsRecordListFree(resourceRecordsPointer, 0);
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}
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return records;
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}
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private static List<DnsSrvRecord> GetSRVRecords(string name)
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{
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IntPtr resourceRecordsPointer = IntPtr.Zero;
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var records = new List<DnsSrvRecord>();
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var retry = 5;
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retry:
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try
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{
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int queryResult = DnsQuery(ref name, NativeDnsQueryTypes.DNS_TYPE_SRV, NativeDnsQueryOptions.DNS_QUERY_STANDARD, 0, ref resourceRecordsPointer, 0);
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if (queryResult != 0)
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{
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if (queryResult == DNS_ERROR_RCODE_NAME_ERROR)
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return records;
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else if (queryResult == DNS_ERROR_BAD_PACKET && retry > 0)
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{
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// Sometimes a BAD_PACKET error is returned, retry a few times
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Thread.Sleep(200);
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retry--;
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goto retry;
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}
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else
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throw new Win32Exception(queryResult);
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}
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NativeDnsSrvRecord record;
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for (var resourceRecordPointer = resourceRecordsPointer; !resourceRecordPointer.Equals(IntPtr.Zero); resourceRecordPointer = record.pNext)
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{
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record = Marshal.PtrToStructure<NativeDnsSrvRecord>(resourceRecordPointer);
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if (record.wType == (ushort)NativeDnsQueryTypes.DNS_TYPE_SRV)
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records.Add(DnsSrvRecord.FromNativeRecord(record));
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}
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}
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finally
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{
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if (resourceRecordsPointer != IntPtr.Zero)
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DnsRecordListFree(resourceRecordsPointer, 0);
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}
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return records;
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}
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private enum NativeDnsQueryOptions
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{
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DNS_QUERY_ACCEPT_TRUNCATED_RESPONSE = 1,
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DNS_QUERY_BYPASS_CACHE = 8,
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DNS_QUERY_DONT_RESET_TTL_VALUES = 0x100000,
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DNS_QUERY_NO_HOSTS_FILE = 0x40,
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DNS_QUERY_NO_LOCAL_NAME = 0x20,
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DNS_QUERY_NO_NETBT = 0x80,
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DNS_QUERY_NO_RECURSION = 4,
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DNS_QUERY_NO_WIRE_QUERY = 0x10,
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DNS_QUERY_RESERVED = -16777216,
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DNS_QUERY_RETURN_MESSAGE = 0x200,
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DNS_QUERY_STANDARD = 0,
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DNS_QUERY_TREAT_AS_FQDN = 0x1000,
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DNS_QUERY_USE_TCP_ONLY = 2,
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DNS_QUERY_WIRE_ONLY = 0x100
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}
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private enum NativeDnsQueryTypes
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{
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DNS_TYPE_TEXT = 0x0010,
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DNS_TYPE_SRV = 0x0021
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}
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[StructLayout(LayoutKind.Sequential)]
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private struct NativeDnsSrvRecord
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{
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public IntPtr pNext;
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[MarshalAs(UnmanagedType.LPWStr)]
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public string pName;
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public ushort wType;
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public ushort wDataLength;
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public int flags;
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public int dwTtl;
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public int dwReserved;
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[MarshalAs(UnmanagedType.LPWStr)]
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public string pNameTarget;
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public ushort wPriority;
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public ushort wWeight;
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public ushort wPort;
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public ushort Pad;
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}
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private class DnsSrvRecord
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{
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public string Name { get; set; }
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public int Type { get; set; }
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public int Ttl { get; set; }
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public string Target { get; set; }
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public int Priority { get; set; }
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public int Weight { get; set; }
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public int Port { get; set; }
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public static DnsSrvRecord FromNativeRecord(NativeDnsSrvRecord nativeRecord)
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{
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return new DnsSrvRecord
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{
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Name = nativeRecord.pName,
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Type = nativeRecord.wType,
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Ttl = nativeRecord.dwTtl,
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Target = nativeRecord.pNameTarget,
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Priority = nativeRecord.wPriority,
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Weight = nativeRecord.wWeight,
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Port = nativeRecord.wPort
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};
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}
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}
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[StructLayout(LayoutKind.Sequential)]
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private struct NativeDnsTxtRecord
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{
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public IntPtr pNext;
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[MarshalAs(UnmanagedType.LPWStr)]
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public string pName;
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public ushort wType;
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public ushort wDataLength;
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public int flags;
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public int dwTtl;
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public int dwReserved;
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public uint dwStringLength;
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[MarshalAs(UnmanagedType.LPWStr)]
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public string pStringArray;
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}
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private class DnsTxtRecord
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{
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public string Name { get; set; }
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public int Type { get; set; }
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public int Ttl { get; set; }
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public string Content { get; set; }
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public static DnsTxtRecord FromNativeRecord(NativeDnsTxtRecord nativeRecord)
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{
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return new DnsTxtRecord
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{
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Name = nativeRecord.pName,
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Type = nativeRecord.wType,
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Ttl = nativeRecord.dwTtl,
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Content = nativeRecord.pStringArray,
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};
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}
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}
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}
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}
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