1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "net/dns/dns_query.h"
6
7#include <limits>
8
9#include "base/big_endian.h"
10#include "base/sys_byteorder.h"
11#include "net/base/dns_util.h"
12#include "net/base/io_buffer.h"
13#include "net/dns/dns_protocol.h"
14
15namespace net {
16
17// DNS query consists of a 12-byte header followed by a question section.
18// For details, see RFC 1035 section 4.1.1.  This header template sets RD
19// bit, which directs the name server to pursue query recursively, and sets
20// the QDCOUNT to 1, meaning the question section has a single entry.
21DnsQuery::DnsQuery(uint16 id, const base::StringPiece& qname, uint16 qtype)
22    : qname_size_(qname.size()) {
23  DCHECK(!DNSDomainToString(qname).empty());
24  // QNAME + QTYPE + QCLASS
25  size_t question_size = qname_size_ + sizeof(uint16) + sizeof(uint16);
26  io_buffer_ = new IOBufferWithSize(sizeof(dns_protocol::Header) +
27                                    question_size);
28  dns_protocol::Header* header =
29      reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
30  memset(header, 0, sizeof(dns_protocol::Header));
31  header->id = base::HostToNet16(id);
32  header->flags = base::HostToNet16(dns_protocol::kFlagRD);
33  header->qdcount = base::HostToNet16(1);
34
35  // Write question section after the header.
36  base::BigEndianWriter writer(reinterpret_cast<char*>(header + 1),
37                               question_size);
38  writer.WriteBytes(qname.data(), qname.size());
39  writer.WriteU16(qtype);
40  writer.WriteU16(dns_protocol::kClassIN);
41}
42
43DnsQuery::~DnsQuery() {
44}
45
46DnsQuery* DnsQuery::CloneWithNewId(uint16 id) const {
47  return new DnsQuery(*this, id);
48}
49
50uint16 DnsQuery::id() const {
51  const dns_protocol::Header* header =
52      reinterpret_cast<const dns_protocol::Header*>(io_buffer_->data());
53  return base::NetToHost16(header->id);
54}
55
56base::StringPiece DnsQuery::qname() const {
57  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
58                           qname_size_);
59}
60
61uint16 DnsQuery::qtype() const {
62  uint16 type;
63  base::ReadBigEndian<uint16>(
64      io_buffer_->data() + sizeof(dns_protocol::Header) + qname_size_, &type);
65  return type;
66}
67
68base::StringPiece DnsQuery::question() const {
69  return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
70                           qname_size_ + sizeof(uint16) + sizeof(uint16));
71}
72
73DnsQuery::DnsQuery(const DnsQuery& orig, uint16 id) {
74  qname_size_ = orig.qname_size_;
75  io_buffer_ = new IOBufferWithSize(orig.io_buffer()->size());
76  memcpy(io_buffer_.get()->data(), orig.io_buffer()->data(),
77         io_buffer_.get()->size());
78  dns_protocol::Header* header =
79      reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
80  header->id = base::HostToNet16(id);
81}
82
83void DnsQuery::set_flags(uint16 flags) {
84  dns_protocol::Header* header =
85      reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
86  header->flags = flags;
87}
88
89}  // namespace net
90