internal static IPHostEntry InternalGetHostByName(string hostName, bool includeIPv6) {
if(Logging.On)Logging.Enter(Logging.Sockets, "DNS", "GetHostByName", hostName);
IPHostEntry ipHostEntry = null;
GlobalLog.Print("Dns.GetHostByName: " + hostName);
if (hostName.Length > MaxHostName // If 255 chars, the last one must be a dot.
|| hostName.Length == MaxHostName && hostName[MaxHostName-1] != '.') {
throw new ArgumentOutOfRangeException("hostName", SR.GetString(SR.net_toolong,
"hostName", MaxHostName.ToString(NumberFormatInfo.CurrentInfo)));
}
//
// IPv6 Changes: IPv6 requires the use of getaddrinfo() rather
// than the traditional IPv4 gethostbyaddr() / gethostbyname().
// getaddrinfo() is also protocol independant in that it will also
// resolve IPv4 names / addresses. As a result, it is the preferred
// resolution mechanism on platforms that support it (Windows 5.1+).
// If getaddrinfo() is unsupported, IPv6 resolution does not work.
//
// Consider : If IPv6 is disabled, we could detect IPv6 addresses
// and throw an unsupported platform exception.
//
// Note : Whilst getaddrinfo is available on WinXP+, we only
// use it if IPv6 is enabled (platform is part of that
// decision). This is done to minimize the number of
// possible tests that are needed.
//
if ( Socket.LegacySupportsIPv6 || includeIPv6) {
//
// IPv6 enabled: use getaddrinfo() to obtain DNS information.
//
ipHostEntry = Dns.GetAddrInfo(hostName);
}
else {
//
// IPv6 disabled: use gethostbyname() to obtain DNS information.
//
IntPtr nativePointer =
UnsafeNclNativeMethods.OSSOCK.gethostbyname(
hostName);
if (nativePointer == IntPtr.Zero) {
// This is for compatiblity with NT4/Win2k
// Need to do this first since if we wait the last error code might be overwritten.
SocketException socketException = new SocketException();
//This block supresses "unknown error" on NT4 when input is
//arbitrary IP address. It simulates same result as on Win2K.
// For Everett compat, we allow this to parse and return IPv6 even when it's disabled.
IPAddress address;
if (IPAddress.TryParse(hostName, out address))
{
ipHostEntry = GetUnresolveAnswer(address);
if(Logging.On)Logging.Exit(Logging.Sockets, "DNS", "GetHostByName", ipHostEntry);
return ipHostEntry;
}
throw socketException;
}
ipHostEntry = NativeToHostEntry(nativePointer);
}
if(Logging.On)Logging.Exit(Logging.Sockets, "DNS", "GetHostByName", ipHostEntry);
return ipHostEntry;
} // GetHostByName
} // NativeToHostEntry
/*****************************************************************************
* Function : gethostbyname
*
* Abstract: Queries DNS for hostname address
*
* Input Parameters: str (String to query)
*
* Returns: Void
******************************************************************************/
/// <include file='doc\DNS.uex' path='docs/doc[@for="Dns.GetHostByName"]/*' />
/// <devdoc>
/// <para>Retrieves the <see cref='System.Net.IPHostEntry'/>
/// information
/// corresponding to the DNS name provided in the host
/// parameter.</para>
/// </devdoc>
public static IPHostEntry GetHostByName(string hostName)
{
//
// demand Unrestricted DnsPermission for this call
//
s_DnsPermission.Demand();
if (hostName == null)
{
throw new ArgumentNullException("hostName");
}
if (hostName.Length > MaxHostName)
{
throw new ArgumentOutOfRangeException(SR.GetString(SR.net_toolong, "hostName", MaxHostName.ToString()));
}
GlobalLog.Print("Dns.GetHostByName: " + hostName);
//
// IPv6 Changes: IPv6 requires the use of getaddrinfo() rather
// than the traditional IPv4 gethostbyaddr() / gethostbyname().
// getaddrinfo() is also protocol independant in that it will also
// resolve IPv4 names / addresses. As a result, it is the preferred
// resolution mechanism on platforms that support it (Windows 5.1+).
// If getaddrinfo() is unsupported, IPv6 resolution does not work.
//
// Consider : If IPv6 is disabled, we could detect IPv6 addresses
// and throw an unsupported platform exception.
//
// Note : Whilst getaddrinfo is available on WinXP+, we only
// use it if IPv6 is enabled (platform is part of that
// decision). This is done to minimize the number of
// possible tests that are needed.
//
if (Socket.SupportsIPv6)
{
//
// IPv6 enabled: use getaddrinfo() to obtain DNS information.
//
return(Dns.GetAddrInfo(hostName));
}
else
{
//
// IPv6 disabled: use gethostbyname() to obtain DNS information.
//
IntPtr nativePointer =
UnsafeNclNativeMethods.OSSOCK.gethostbyname(
hostName);
if (nativePointer == IntPtr.Zero)
{
//This is for compatiblity with NT4
SocketException e = new SocketException();
//This block supresses "unknown error" on NT4 when input is
//arbitrary IP address. It simulates same result as on Win2K.
try {
IPAddress address = IPAddress.Parse(hostName);
IPHostEntry ipHostEntry = new IPHostEntry();
ipHostEntry.HostName = string.Copy(hostName);
ipHostEntry.Aliases = new string[0];
ipHostEntry.AddressList = new IPAddress[] { address };
return(ipHostEntry);
}
catch {
//Report original DNS error (not from IPAddress.Parse())
throw e;
}
}
return(NativeToHostEntry(nativePointer));
}
} // GetHostByName
