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      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 
     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   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 
     43 DnsQuery::~DnsQuery() {
     44 }
     45 
     46 DnsQuery* DnsQuery::CloneWithNewId(uint16 id) const {
     47   return new DnsQuery(*this, id);
     48 }
     49 
     50 uint16 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 
     56 base::StringPiece DnsQuery::qname() const {
     57   return base::StringPiece(io_buffer_->data() + sizeof(dns_protocol::Header),
     58                            qname_size_);
     59 }
     60 
     61 uint16 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 
     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
     90