148 lines
4.7 KiB
C#
148 lines
4.7 KiB
C#
//----------------------------------------------------------------------------
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//----------------------------------------------------------------------------
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namespace System.ServiceModel.Channels
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{
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Net;
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using System.Net.NetworkInformation;
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using System.Net.Sockets;
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using System.Runtime;
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using System.Security.Permissions;
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using System.ServiceModel;
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using System.ServiceModel.Dispatcher;
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using System.Text;
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static class DnsCache
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{
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const int mruWatermark = 64;
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static MruCache<string, DnsCacheEntry> resolveCache = new MruCache<string, DnsCacheEntry>(mruWatermark);
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static readonly TimeSpan cacheTimeout = TimeSpan.FromSeconds(2);
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// Double-checked locking pattern requires volatile for read/write synchronization
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static volatile string machineName;
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static object ThisLock
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{
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get
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{
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return resolveCache;
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}
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}
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public static string MachineName
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{
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get
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{
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if (machineName == null)
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{
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lock (ThisLock)
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{
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if (machineName == null)
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{
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try
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{
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machineName = Dns.GetHostEntry(String.Empty).HostName;
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}
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catch (SocketException exception)
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{
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DiagnosticUtility.TraceHandledException(exception,
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TraceEventType.Information);
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// we fall back to the NetBios machine if Dns fails
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machineName = UnsafeNativeMethods.GetComputerName(ComputerNameFormat.PhysicalNetBIOS);
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}
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}
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}
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}
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return machineName;
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}
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}
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public static IPHostEntry Resolve(Uri uri)
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{
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string hostName = uri.DnsSafeHost;
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IPHostEntry hostEntry = null;
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DateTime now = DateTime.UtcNow;
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lock (ThisLock)
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{
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DnsCacheEntry cacheEntry;
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if (resolveCache.TryGetValue(hostName, out cacheEntry))
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{
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if (now.Subtract(cacheEntry.TimeStamp) > cacheTimeout)
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{
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resolveCache.Remove(hostName);
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}
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else
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{
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if (cacheEntry.HostEntry == null)
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{
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throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(
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new EndpointNotFoundException(SR.GetString(SR.DnsResolveFailed, hostName)));
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}
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hostEntry = cacheEntry.HostEntry;
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}
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}
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}
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if (hostEntry == null)
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{
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SocketException dnsException = null;
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try
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{
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hostEntry = Dns.GetHostEntry(hostName);
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}
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catch (SocketException e)
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{
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dnsException = e;
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}
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lock (ThisLock)
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{
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// MruCache doesn't have a this[] operator, so we first remove (just in case it exists already)
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resolveCache.Remove(hostName);
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resolveCache.Add(hostName, new DnsCacheEntry(hostEntry, now));
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}
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if (dnsException != null)
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{
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throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(
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new EndpointNotFoundException(SR.GetString(SR.DnsResolveFailed, hostName), dnsException));
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}
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}
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return hostEntry;
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}
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class DnsCacheEntry
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{
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IPHostEntry hostEntry;
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DateTime timeStamp;
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public DnsCacheEntry(IPHostEntry hostEntry, DateTime timeStamp)
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{
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this.hostEntry = hostEntry;
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this.timeStamp = timeStamp;
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}
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public IPHostEntry HostEntry
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{
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get
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{
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return hostEntry;
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}
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}
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public DateTime TimeStamp
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{
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get
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{
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return timeStamp;
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}
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}
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}
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}
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}
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