public void DnsSerialization_NameCompression()
{
DnsMessage message = new DnsMessage();
Dictionary <string, int> namePtrs = new Dictionary <string, int>();
int offset;
byte[] packet;
string name;
message.SetNamePtrs(namePtrs);
// Verify that labels greater than 63 characters throw
// an exception.
try
{
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, new String('a', 64) + ".com.");
Assert.Fail("Exception expected");
}
catch
{
}
// Verify that zero length internal labels throw
// an exception.
try
{
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "test..com.");
Assert.Fail("Exception expected");
}
catch
{
}
// Verify that relative domain names throw an exception.
try
{
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "test.com");
Assert.Fail("Exception expected");
}
catch
{
}
// Verify writing the root domain by itself.
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, ".");
Assert.AreEqual(1, offset);
Assert.AreEqual(0, packet[0]);
Assert.AreEqual(0, namePtrs.Count);
// Verify writing a domain with a single label.
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "a.");
Assert.AreEqual(3, offset);
Assert.AreEqual(1, packet[0]);
Assert.AreEqual('a', (char)packet[1]);
Assert.AreEqual(0, packet[2]);
Assert.AreEqual(1, namePtrs.Count);
Assert.AreEqual(0, namePtrs["a"]);
// Verify writing a domain with a three labels.
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "a.b.c.");
Assert.AreEqual(7, offset);
Assert.AreEqual(1, packet[0]);
Assert.AreEqual('a', (char)packet[1]);
Assert.AreEqual(1, packet[2]);
Assert.AreEqual('b', (char)packet[3]);
Assert.AreEqual(1, packet[4]);
Assert.AreEqual('c', (char)packet[5]);
Assert.AreEqual(0, packet[6]);
Assert.AreEqual(3, namePtrs.Count);
Assert.AreEqual(0, namePtrs["a.b.c"]);
Assert.AreEqual(2, namePtrs["b.c"]);
Assert.AreEqual(4, namePtrs["c"]);
// Write the entire three label domain and verify
// that only a pointer is written.
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "a.b.c.");
message.WriteName(packet, ref offset, "a.b.c.");
Assert.AreEqual(9, offset);
Assert.AreEqual(0xC0, packet[7]);
Assert.AreEqual(0, packet[8]);
// Verify that after writing "a.b.c." and then
// writing "z.b.c." that a pointer is written
// for the "b.c." portion.
namePtrs.Clear();
packet = new byte[512];
offset = 0;
message.WriteName(packet, ref offset, "a.b.c.");
message.WriteName(packet, ref offset, "z.b.c.");
Assert.AreEqual(11, offset);
Assert.AreEqual(1, packet[7]);
Assert.AreEqual('z', (char)packet[8]);
Assert.AreEqual(0xC0, packet[9]);
Assert.AreEqual(2, packet[10]);
// Verify that we can read the two domains just written.
offset = 0;
message.ReadName(packet, ref offset, out name);
Assert.AreEqual("a.b.c.", name);
message.ReadName(packet, ref offset, out name);
Assert.AreEqual("z.b.c.", name);
}
