internal IPv6Address GetRandomPrefix(HashSet <IPv6Address> hashedUsedPrefixes)
{
Random random = new Random();
Byte[] addressBytes = new byte[16];
IPv6SubnetMask mask = new IPv6SubnetMask(new IPv6SubnetMaskIdentifier(PrefixDelgationInfo.PrefixLength));
Byte[] addressMaskBytes = mask.GetMaskBytes();
Byte[] ipAddressBytes = PrefixDelgationInfo.Prefix.GetBytes();
IPv6SubnetMask delegatedMask = new IPv6SubnetMask(new IPv6SubnetMaskIdentifier(PrefixDelgationInfo.AssignedPrefixLength));
Byte[] delegatedMaskBytes = delegatedMask.GetMaskBytes();
Int32 randomizationIndex = -1;
for (int i = 0; i < 16; i++)
{
if (addressMaskBytes[i] != 255)
{
randomizationIndex = i;
break;
}
else
{
addressBytes[i] = ipAddressBytes[i];
}
}
IPv6Address nextNetworkAddress;
Int32 trysLeft = _maxTriesForRandom;
do
{
if (randomizationIndex >= 0)
{
Boolean lengthAndAssigendLengthInSameByte = PrefixDelgationInfo.PrefixLength / 8 == (PrefixDelgationInfo.AssignedPrefixLength - 1) / 8;
if (lengthAndAssigendLengthInSameByte == true)
{
Byte diff = (Byte)(delegatedMaskBytes[randomizationIndex] - addressMaskBytes[randomizationIndex]);
ByteHelper.AddRandomBits(random, addressBytes, randomizationIndex, diff, ipAddressBytes[randomizationIndex]);
}
else
{
addressBytes[randomizationIndex] = (Byte)(addressMaskBytes[randomizationIndex] + random.Next(0, 255 - addressMaskBytes[randomizationIndex] + 1));
}
for (int i = randomizationIndex + 1; i < 16; i++)
{
if (delegatedMaskBytes[i] == 255)
{
addressBytes[i] = (Byte)random.Next(0, 256);
}
else
{
addressBytes[i] = (Byte)(random.Next(0, delegatedMaskBytes[i]));
ByteHelper.AddRandomBits(random, addressBytes, i, delegatedMaskBytes[i], 0);
break;
}
}
}
nextNetworkAddress = IPv6Address.FromByteArray(addressBytes);
} while (trysLeft-- > 0 && hashedUsedPrefixes.Contains(nextNetworkAddress) == true);
return(nextNetworkAddress);
}
