Added DnsQuery class

net/base/dns_query.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 <string>
+
+#include "base/rand_util.h"
+#include "net/base/address_family.h"
+#include "net/base/dns_util.h"
+
+#include <iostream>
+
+namespace net {
+
+namespace {
+
+void PackUint16BE(char buf[2], uint16 v) {
+  buf[1] = v & 0xff;
+  buf[0] = v >> 8;
+}
+
+}
+
+// DNS query consists of a 12-byte header followed by a question section,
+// for details, see RFC 1035 section 4.1.1.  This header template sets RD
+// bit, which directs the name server to pursue query recursively, and sets
+// the QDCOUNT to 1, meaning the question section has a single entry.  The
+// first two bytes of the header form a 16-bit query ID to be copied in the
+// corresponding reply by the name server; it's set to 0 here and is
+// randomized every time the underlying buffer is fetched.
+static const char kHeader[] = {0x00, 0x00, 0x01, 0x00, 0x00, 0x01,
+                               0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+static const int kHeaderLen = arraysize(kHeader);
+
+DnsQuery::DnsQuery(const std::string& hostname,
+                   AddressFamily address_family,
+                   int port)
+    : port_(port),
+      id_(0),
+      qtype_(kDNS_A),

[cbentzel, 2011/05/26 17:32:40]

I'd add a function such as QtypeFromAddressFamily() so qtype_ is only
initialized once. This can just be in the anonymous namespace.

[agayev, 2011/05/26 22:55:55]

Done.

+      qclass_(kClassIN) {
+  if (address_family == ADDRESS_FAMILY_IPV6)
+    qtype_ = kDNS_AAAA;
+  else if (address_family != ADDRESS_FAMILY_IPV4)
+    NOTREACHED();
+
+  if (!net::DNSDomainFromDot(hostname, &qname_))
+    return;
+
+  size_t query_size = kHeaderLen + qname_.size() +
+    sizeof(qtype_) + sizeof(qclass_);
+  std::vector<char> query(query_size);

[cbentzel, 2011/05/26 17:32:40]

Why don't you do this directly into the IOBuffer? This is causing additional
memory copies [from the vector<char> to the io_buffer_->data()], additional
memory allocations/frees, and default constructors. I'm also a bit worried about
memcpy'ing directly into the vector's data. 

[agayev, 2011/05/26 22:55:55]

Done.

+
+  size_t iterator = 0;
+  memcpy(&query[iterator], kHeader, kHeaderLen);
+  iterator += kHeaderLen;
+  memcpy(&query[iterator], &qname_[0], qname_.size());
+  iterator += qname_.size();
+  PackUint16BE(&query[iterator], qtype_);
+  iterator += sizeof(qtype_);
+  PackUint16BE(&query[iterator], qclass_);
+
+  io_buffer_ = new IOBufferWithSize(query.size());
+  memcpy(io_buffer_->data(), &query[0], query.size());
+
+  RandomizeId();
+  // RFC2181 section 11: A full domain name is limited to 255 octets
+  // (including the separators).
+  static const int kMaxQuerySize = kHeaderLen + 255 +
+    sizeof(qtype_) + sizeof(qclass_);
+  DCHECK(io_buffer_->size() > kHeaderLen &&
+         io_buffer_->size() <= kMaxQuerySize);
+}
+
+void DnsQuery::RandomizeId() {
+  DCHECK(IsValid());
+  id_ = base::RandUint64() & 0xffff;

[cbentzel, 2011/05/26 17:32:40]

Is this random enough? I haven't looked. 

[agayev, 2011/05/26 22:55:55]

This is the primitive used by all other randomness functions.

+  PackUint16BE(io_buffer_->data(), id_);

[cbentzel, 2011/05/26 17:32:40]

You should probably use htons here. 

[agayev, 2011/05/26 22:55:55]

No, since I'm doing it big-endian anyway.

+}
+
+int DnsQuery::port() const {
+  DCHECK(IsValid());
+  return port_;
+}
+
+uint16 DnsQuery::id() const {
+  DCHECK(IsValid());
+  return id_;
+}
+
+uint16 DnsQuery::qtype() const {
+  DCHECK(IsValid());
+  return qtype_;
+}
+
+uint16 DnsQuery::qclass() const {
+  DCHECK(IsValid());
+  return qclass_;
+}
+
+const std::string& DnsQuery::qname() const {
+  DCHECK(IsValid());
+  return qname_;
+}
+
+size_t DnsQuery::size() const {
+  DCHECK(IsValid());
+  return io_buffer_->size();
+}
+
+IOBuffer* DnsQuery::io_buffer() {
+  DCHECK(IsValid());
+  RandomizeId();
+  return io_buffer_.get();
+}
+
+char* DnsQuery::data() const {
+  DCHECK(IsValid());
+  return io_buffer_->data();
+}
+
+}  // namespace net