Added DnsQuery class

net/base/dns_query_unittest.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/base/dns_query.h"
+#include "net/base/dns_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+
+// DNS query consists of a header followed by a question.  Header format
+// and question format are described below.  For the meaning of specific
+// fields, please see RFC 1035.
+
+// Header format.
+//                                  1  1  1  1  1  1
+//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      ID                       |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |QR|   Opcode  |AA|TC|RD|RA|   Z    |   RCODE   |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    QDCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ANCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    NSCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ARCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+// Question format.
+//                                  1  1  1  1  1  1
+//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                                               |
+//  /                     QNAME                     /
+//  /                                               /
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     QTYPE                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     QCLASS                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+TEST(DnsQueryTest, ConstructorTest) {
+  const std::string kHostname = "www.google.com";
+  const int kPort = 80;
+
+  DnsQuery q1(kHostname, ADDRESS_FAMILY_IPV4, kPort);
+  EXPECT_TRUE(q1.IsValid());
+  EXPECT_EQ(kPort, q1.port());
+  EXPECT_EQ(kDNS_A, q1.qtype());
+  EXPECT_EQ(kHostname, q1.hostname());
+
+  uint8 id_hi = q1.id() >> 8, id_lo = q1.id() & 0xff;

[cbentzel, 2011/06/01 17:17:03]

I'm pretty sure this will do a logical shift instead of an arithmetic shift, but
maybe mask id_hi with 0xff to make sure?

[agayev, 2011/06/01 19:15:01]

id_hi is a single byte, masking it with 0xff is a no-op.  Do you really want
that?

[cbentzel, 2011/06/01 19:41:21]

Oops, I was thinking of it as uint16. No, the mask is not necessary.

+
+  // See the top of the file for the description of a DNS query.
+  const uint8 query_data[] = {
+    // Header
+    id_hi, id_lo,
+    0x01, 0x00,               // Flags -- set RD (recursion desired) bit.
+    0x00, 0x01,               // Set QDCOUNT (question count) to 1, all the
+                              // rest are 0 for a query.
+    0x00, 0x00,
+    0x00, 0x00,
+    0x00, 0x00,
+
+    // Question
+    0x03, 0x77, 0x77, 0x77,   // QNAME: www.google.com in DNS format.
+    0x06, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65,
+    0x03, 0x63, 0x6f, 0x6d, 0x00,
+
+    0x00, 0x01,               // QTYPE: A query
+    0x00, 0x01,               // QCLASS: IN class
+  };
+
+  int expected_size = arraysize(query_data);
+  EXPECT_EQ(expected_size, q1.size());
+  EXPECT_EQ(0, memcmp(q1.data(), query_data, q1.size()));
+
+  // Query with a long hostname.
+  const char hostname_too_long[] = "123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.123456789.1234";
+
+  DnsQuery q2(hostname_too_long, ADDRESS_FAMILY_IPV4, 80);
+  EXPECT_FALSE(q2.IsValid());
+}
+
+TEST(DnsQueryTest, IOBufferAccessRandomizesIdTest) {
+  const std::string kHostname = "www.google.com";
+  const int kPort = 80;
+
+  DnsQuery q1(kHostname, ADDRESS_FAMILY_IPV4, kPort);
+  EXPECT_TRUE(q1.IsValid());
+  EXPECT_EQ(kPort, q1.port());
+  EXPECT_EQ(kDNS_A, q1.qtype());
+  EXPECT_EQ(kHostname, q1.hostname());
+
+  uint8 id_hi = q1.id() >> 8, id_lo = q1.id() & 0xff;
+
+  // See the top of the file for the description of a DNS query.
+  uint8 query_data[] = {
+    // Header
+    id_hi, id_lo,
+    0x01, 0x00,               // Flags -- set RD (recursion desired) bit.
+    0x00, 0x01,               // Set QDCOUNT (question count) to 1, all the
+                              // rest are 0 for a query.
+    0x00, 0x00,
+    0x00, 0x00,
+    0x00, 0x00,
+
+    // Question
+    0x03, 0x77, 0x77, 0x77,   // QNAME: www.google.com in DNS format.
+    0x06, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65,
+    0x03, 0x63, 0x6f, 0x6d, 0x00,
+
+    0x00, 0x01,               // QTYPE: A query
+    0x00, 0x01,               // QCLASS: IN class
+  };
+
+  int expected_size = arraysize(query_data);
+  EXPECT_EQ(expected_size, q1.size());
+  EXPECT_EQ(0, memcmp(q1.data(), query_data, q1.size()));
+
+  q1.io_buffer();             // Simulate a write, ID has changed.
+  EXPECT_FALSE(id_hi == q1.data()[0]);

[cbentzel, 2011/06/01 17:17:03]

The bytes will occasionally match, so this test will fail about .8% of the time
(1 - (255/256)^2) assuming pure randomness.

I'd suggest removing it.

[agayev, 2011/06/01 19:15:01]

Decreased the probability of a failure to 1/2^16, is that good enough?

+  EXPECT_FALSE(id_lo == q1.data()[1]);
+}
+
+}  // namespace net