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// Copyright (c) 2012 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/dns/dns_query.h"
#include "base/big_endian.h"
#include "base/memory/ptr_util.h"
#include "base/sys_byteorder.h"
#include "net/base/io_buffer.h"
#include "net/dns/dns_protocol.h"
#include "net/dns/dns_util.h"
#include "net/dns/record_rdata.h"
namespace net {
namespace {
const size_t kHeaderSize = sizeof(dns_protocol::Header);
// Size of the fixed part of an OPT RR:
// https://tools.ietf.org/html/rfc6891#section-6.1.2
static const size_t kOptRRFixedSize = 11;
// https://tools.ietf.org/html/rfc6891#section-6.2.5
// TODO(robpercival): Determine a good value for this programmatically.
const uint16_t kMaxUdpPayloadSize = 4096;
size_t OptRecordSize(const OptRecordRdata* rdata) {
return rdata == nullptr ? 0 : kOptRRFixedSize + rdata->buf().size();
}
} // namespace
// DNS query consists of a 12-byte header followed by a question section.
// 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.
DnsQuery::DnsQuery(uint16_t id,
const base::StringPiece& qname,
uint16_t qtype,
const OptRecordRdata* opt_rdata)
: qname_size_(qname.size()),
io_buffer_(new IOBufferWithSize(kHeaderSize + question_size() +
OptRecordSize(opt_rdata))),
header_(reinterpret_cast<dns_protocol::Header*>(io_buffer_->data())) {
DCHECK(!DNSDomainToString(qname).empty());
*header_ = {};
header_->id = base::HostToNet16(id);
header_->flags = base::HostToNet16(dns_protocol::kFlagRD);
header_->qdcount = base::HostToNet16(1);
// Write question section after the header.
base::BigEndianWriter writer(io_buffer_->data() + kHeaderSize,
io_buffer_->size() - kHeaderSize);
writer.WriteBytes(qname.data(), qname.size());
writer.WriteU16(qtype);
writer.WriteU16(dns_protocol::kClassIN);
if (opt_rdata != nullptr) {
header_->arcount = base::HostToNet16(1);
// Write OPT pseudo-resource record.
writer.WriteU8(0); // empty domain name (root domain)
writer.WriteU16(OptRecordRdata::kType); // type
writer.WriteU16(kMaxUdpPayloadSize); // class
// ttl (next 3 fields)
writer.WriteU8(0); // rcode does not apply to requests
writer.WriteU8(0); // version
// TODO(robpercival): Set "DNSSEC OK" flag if/when DNSSEC is supported:
// https://tools.ietf.org/html/rfc3225#section-3
writer.WriteU16(0); // flags
// rdata
writer.WriteU16(opt_rdata->buf().size()); // rdata length
writer.WriteBytes(opt_rdata->buf().data(), opt_rdata->buf().size());
}
}
DnsQuery::~DnsQuery() = default;
std::unique_ptr<DnsQuery> DnsQuery::CloneWithNewId(uint16_t id) const {
return base::WrapUnique(new DnsQuery(*this, id));
}
uint16_t DnsQuery::id() const {
return base::NetToHost16(header_->id);
}
base::StringPiece DnsQuery::qname() const {
return base::StringPiece(io_buffer_->data() + kHeaderSize, qname_size_);
}
uint16_t DnsQuery::qtype() const {
uint16_t type;
base::ReadBigEndian<uint16_t>(io_buffer_->data() + kHeaderSize + qname_size_,
&type);
return type;
}
base::StringPiece DnsQuery::question() const {
return base::StringPiece(io_buffer_->data() + kHeaderSize, question_size());
}
void DnsQuery::set_flags(uint16_t flags) {
header_->flags = flags;
}
DnsQuery::DnsQuery(const DnsQuery& orig, uint16_t id) {
qname_size_ = orig.qname_size_;
io_buffer_ = new IOBufferWithSize(orig.io_buffer()->size());
memcpy(io_buffer_.get()->data(), orig.io_buffer()->data(),
io_buffer_.get()->size());
header_ = reinterpret_cast<dns_protocol::Header*>(io_buffer_->data());
header_->id = base::HostToNet16(id);
}
} // namespace net
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