Added DnsQuery class

net/base/dns_query.h

+// 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.
+
+#ifndef NET_BASE_DNS_QUERY_H_
+#define NET_BASE_DNS_QUERY_H_
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "net/base/address_family.h"
+#include "net/base/io_buffer.h"
+
+namespace net{
+
+// A class that encapsulates bits and pieces related to DNS request processing.

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

Right now this is A and AAAA only. Do you want to expand this to support
arbitrary queries? To allow more than one query? To specify whether recursion is
allowed/denied?

I'm fine with leaving it simple now, but it might be nice to have general
framers and parsers API for any DNS message. 

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

We will probably want most of that, but I'd rather do it incrementally.

+class DnsQuery {
+ public:
+  // Constructs an object containing an IOBuffer with raw DNS query string
+  // for |hostname| with the given |address_family|; |port| is here due to
+  // legacy -- getaddrinfo() takes service name, which is mapped to some
+  // port and returns sockaddr_in structures with ports filled in, so do we
+  // -- look at DnsResponse::Parse() to see where it is used.
+  DnsQuery(const std::string& hostname, AddressFamily address_family, int port);
+
+  // Returns true if the constructed object was valid.
+  bool IsValid() const { return io_buffer_.get() != NULL; }
+
+  // DnsQuery field accessors.
+  int port() const;
+  uint16 id() const;
+  uint16 qtype() const;
+  uint16 qclass() const;
+  const std::string& qname() const;
+
+  // Returns the size of the query in number of bytes.
+  size_t size() const;
+
+  // IOBuffer accessor to be used for writing out the query.  This has a
+  // side effect of randomizing the ID portion of a query buffer.
+  IOBuffer* io_buffer();
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(DnsQueryTest, ConstructorTest);
+  FRIEND_TEST_ALL_PREFIXES(DnsQueryTest, IOBufferAccessRandomizesIdTest);
+
+  // Randomizes ID field in the IOBuffer, also sets |id_|.
+  void RandomizeId();
+
+  // Gives access to the query bytes without randomizing ID field, used by
+  // tests.
+  char* data() const;
+
+  // Port to be used by corresponding DnsResponse when filling sockaddr_ins
+  // to be returned.
+  int port_;
+
+  // ID of the query; changes on each io_buffer_ access.
+  uint16 id_;
+
+  // Type of query, currently, either A or AAAA.
+  uint16 qtype_;
+
+  // Class of query, currently fixed to IN class.
+  uint16 qclass_;
+
+  // Hostname in DNS format.
+  std::string qname_;
+
+  // Contains query bytes to be consumed by higher level Write() call.
+  scoped_refptr<IOBufferWithSize> io_buffer_;
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_DNS_QUERY_H_