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// 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.
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <string>
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/strings/string_piece.h"
#include "net/base/net_export.h"
namespace base {
class BigEndianReader;
} // namespace base
namespace net {
class OptRecordRdata;
namespace dns_protocol {
struct Header;
} // namespace dns_protocol
class IOBufferWithSize;
// Represents on-the-wire DNS query message as an object.
enum class PaddingStrategy {
// Query will not be padded. Recommended strategy when query will not be
// encrypted.
// Query will be padded to the next multiple of 128 octets. Recommended
// strategy (per RFC 8467) when query will be encrypted, e.g. through
// DNS-over-HTTPS.
// Constructs a query message from |qname| which *MUST* be in a valid
// DNS name format, and |qtype|. The qclass is set to IN.
// If |opt_rdata| is not null, an OPT record will be added to the "Additional"
// section of the query.
DnsQuery(uint16_t id,
const base::StringPiece& qname,
uint16_t qtype,
const OptRecordRdata* opt_rdata = nullptr,
PaddingStrategy padding_strategy = PaddingStrategy::NONE);
// Constructs an empty query from a raw packet in |buffer|. If the raw packet
// represents a valid DNS query in the wire format (RFC 1035), Parse() will
// populate the empty query.
explicit DnsQuery(scoped_refptr<IOBufferWithSize> buffer);
// Copies are constructed with an independent cloned, not mirrored, buffer.
DnsQuery(const DnsQuery& query);
DnsQuery& operator=(const DnsQuery& query);
// Clones |this| verbatim, with ID field of the header set to |id|.
std::unique_ptr<DnsQuery> CloneWithNewId(uint16_t id) const;
// Returns true and populates the query if the internally stored raw packet
// can be parsed. This should only be called when DnsQuery is constructed from
// the raw buffer.
// |valid_bytes| indicates the number of initialized bytes in the raw buffer.
// E.g. if the buffer holds a packet received from the network, the buffer may
// be allocated with the maximum size of a UDP packet, but |valid_bytes|
// indicates the number of bytes actually received from the network. If the
// parsing requires reading more than the number of initialized bytes, this
// method fails and returns false.
bool Parse(size_t valid_bytes);
// DnsQuery field accessors.
uint16_t id() const;
base::StringPiece qname() const;
uint16_t qtype() const;
// Returns the Question section of the query. Used when matching the
// response.
base::StringPiece question() const;
// Returns the size of the question section.
size_t question_size() const;
// IOBuffer accessor to be used for writing out the query. The buffer has
// the same byte layout as the DNS query wire format.
IOBufferWithSize* io_buffer() const { return io_buffer_.get(); }
void set_flags(uint16_t flags);
DnsQuery(const DnsQuery& orig, uint16_t id);
void CopyFrom(const DnsQuery& orig);
bool ReadHeader(base::BigEndianReader* reader, dns_protocol::Header* out);
// After read, |out| is in the DNS format, e.g.
// "\x03""www""\x08""chromium""\x03""com""\x00". Use DNSDomainToString to
// convert to the dotted format "" with no trailing dot.
bool ReadName(base::BigEndianReader* reader, std::string* out);
// Size of the DNS name (*NOT* hostname) we are trying to resolve; used
// to calculate offsets.
size_t qname_size_ = 0;
// Contains query bytes to be consumed by higher level Write() call.
scoped_refptr<IOBufferWithSize> io_buffer_;
// Pointer to the dns header section.
dns_protocol::Header* header_ = nullptr;
} // namespace net
#endif // NET_DNS_DNS_QUERY_H_