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;

[agl, 2011/05/30 18:35:30]

please flip these two lines.

[agayev, 2011/05/31 15:19:06]

Will do.

+  buf[0] = v >> 8;
+}
+
+uint16 QTypeFromAddressFamily(AddressFamily address_family) {
+  uint16 qtype = kDNS_A;

[agl, 2011/05/30 18:35:30]

switch (address_family) {
  case ADDRESS_FAMILY_IPV4:
    return kDNS_A;
  case ADDRESS_FAMILY_IPV6:
    return kDNS_AAAA;
  default:
    NOTREACHED() << "Bad address family";
    return kDNS_A;
}

[agayev, 2011/05/31 15:19:06]

Will do.

+  if (address_family == ADDRESS_FAMILY_IPV6)
+    qtype = kDNS_AAAA;
+  else if (address_family != ADDRESS_FAMILY_IPV4)
+    NOTREACHED() << "Bad address family";
+  return qtype;
+}
+
+}
+
+// DNS query consists of a 12-byte header followed by a question section,

[agl, 2011/05/30 18:35:30]

s/section,/section./ (and s/for/For/ on the next line)

[agayev, 2011/05/31 15:19:06]

Will do.

+// 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);

[agl, 2011/05/30 18:35:30]

s/int/size_t/

[agayev, 2011/05/31 15:19:06]

Same argument as previous one regarding int vs size_t, but will do.

+
+DnsQuery::DnsQuery(const std::string& hostname,
+                   AddressFamily address_family,
+                   int port)
+    : port_(port),
+      id_(0),
+      qtype_(QTypeFromAddressFamily(address_family)),
+      qclass_(kClassIN),
+      hostname_(hostname) {
+  std::string qname;
+  if (!net::DNSDomainFromDot(hostname, &qname))
+    return;
+
+  size_t query_size = kHeaderLen + qname.size() +
+    sizeof(qtype_) + sizeof(qclass_);
+
+  io_buffer_ = new IOBufferWithSize(query_size);
+
+  int iterator = 0;
+  memcpy(&io_buffer_->data()[iterator], kHeader, kHeaderLen);
+  iterator += kHeaderLen;
+  memcpy(&io_buffer_->data()[iterator], &qname[0], qname.size());
+  iterator += qname.size();
+  PackUint16BE(&io_buffer_->data()[iterator], qtype_);
+  iterator += sizeof(qtype_);
+  PackUint16BE(&io_buffer_->data()[iterator], qclass_);
+  iterator += sizeof(qclass_);
+
+  // RFC2181 section 11: A full domain name is limited to 255 octets
+  // (including the separators).
+  static const int kMaxQuerySize = kHeaderLen + 255 +

[agl, 2011/05/30 18:35:30]

DNSDomainFromDot should fail if the name is too long, rendering this test
superfluous.

[agayev, 2011/05/31 15:19:06]

Will do.

+    sizeof(qtype_) + sizeof(qclass_);
+
+  DCHECK(iterator <= kMaxQuerySize);

[cbentzel, 2011/05/27 15:15:54]

This shouldn't be a DCHECK - unless there are checks on hostname length from all
callers of this function.

I also think it would make more sense to do this earlier - like when query_size
is calculated and before the io_buffer_ is created, so IsValid() will return
false. 

[agayev, 2011/05/31 15:19:06]

Will do.

+  DCHECK(io_buffer_->size() > kHeaderLen && io_buffer_->size() <= kMaxQuerySize);
+
+  RandomizeId();
+}
+
+void DnsQuery::RandomizeId() {
+  DCHECK(IsValid());
+  id_ = base::RandUint64() & 0xffff;
+  PackUint16BE(io_buffer_->data(), id_);
+}
+
+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::hostname() const {
+  DCHECK(IsValid());
+  return hostname_;
+}
+
+int 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