net/dns/dns_query.cc

   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/sys_byteorder.h"
  10 #include "net/base/big_endian.h"
  11 #include "net/base/dns_util.h"
  12 #include "net/base/io_buffer.h"
  13 #include "net/dns/dns_protocol.h"
  14
  15 namespace 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.
  21 DnsQuery::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   BigEndianWriter writer(reinterpret_cast<char*>(header + 1), question_size);
  37   writer.WriteBytes(qname.data(), qname.size());
  38   writer.WriteU16(qtype);
  39   writer.WriteU16(dns_protocol::kClassIN);
  40 }
  41
  42 DnsQuery::~DnsQuery() {
  43 }
  44
  45 DnsQuery* DnsQuery::CloneWithNewId(uint16 id) const {
  46   return new DnsQuery(*this, id);
  47 }
  48
  49 uint16 DnsQuery::id() const {
  50   const dns_protocol::Header* header =
  51       reinterpret_cast<const dns_protocol::Header*>(io_buffer_->data());
  52   return base::NetToHost16(header->id);
  53 }
  54
  55 base::StringPiece DnsQuery::qname() const {
  56   return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
  57                            qname_size_);
  58 }
  59
  60 uint16 DnsQuery::qtype() const {
  61   uint16 type;
  62   ReadBigEndian<uint16>(io_buffer_->data() +
  63                         sizeof(dns_protocol::Header) +
  64                         qname_size_, &type);
  65   return type;
  66 }
  67
  68 base::StringPiece DnsQuery::question() const {
  69   return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
  70                            qname_size_ + sizeof(uint16) + sizeof(uint16));
  71 }
  72
  73 DnsQuery::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
  83 void 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