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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.
#ifndef NET_DNS_DNS_RESPONSE_H_
#define NET_DNS_DNS_RESPONSE_H_
#pragma once
#include <string>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/string_piece.h"
#include "net/base/net_export.h"
#include "net/base/net_util.h"
namespace net {
class DnsQuery;
class IOBufferWithSize;
namespace dns_protocol {
struct Header;
}
// Parsed resource record.
struct NET_EXPORT_PRIVATE DnsResourceRecord {
std::string name; // in dotted form
uint16 type;
uint16 klass;
uint32 ttl;
base::StringPiece rdata; // points to the original response buffer
};
// Iterator to walk over resource records of the DNS response packet.
class NET_EXPORT_PRIVATE DnsRecordParser {
public:
// Construct an uninitialized iterator.
DnsRecordParser();
// Construct an iterator to process the |packet| of given |length|.
// |offset| points to the beginning of the answer section.
DnsRecordParser(const void* packet, size_t length, size_t offset);
// Returns |true| if initialized.
bool IsValid() const { return packet_ != NULL; }
// Returns |true| if no more bytes remain in the packet.
bool AtEnd() const { return cur_ == packet_ + length_; }
// Parses a (possibly compressed) DNS name from the packet starting at
// |pos|. Stores output (even partial) in |out| unless |out| is NULL. |out|
// is stored in the dotted form, e.g., "example.com". Returns number of bytes
// consumed or 0 on failure.
// This is exposed to allow parsing compressed names within RRDATA for TYPEs
// such as NS, CNAME, PTR, MX, SOA.
// See RFC 1035 section 4.1.4.
int ParseName(const void* pos, std::string* out) const;
// Parses the next resource record. Returns true if succeeded.
bool ParseRecord(DnsResourceRecord* record);
private:
const char* packet_;
size_t length_;
// Current offset within the packet.
const char* cur_;
};
// Buffer-holder for the DNS response allowing easy access to the header fields
// and resource records. After reading into |io_buffer| must call InitParse to
// position the RR parser.
class NET_EXPORT_PRIVATE DnsResponse {
public:
// Constructs an object with an IOBuffer large enough to read
// one byte more than largest possible response, to detect malformed
// responses.
DnsResponse();
// Constructs response from |data|. Used for testing purposes only!
DnsResponse(const void* data, size_t length, size_t answer_offset);
~DnsResponse();
// Internal buffer accessor into which actual bytes of response will be
// read.
IOBufferWithSize* io_buffer() { return io_buffer_.get(); }
// Returns false if the packet is shorter than the header or does not match
// |query| id or question.
bool InitParse(int nbytes, const DnsQuery& query);
// Accessors for the header.
uint8 flags0() const; // first byte of flags
uint8 flags1() const; // second byte of flags excluding rcode
uint8 rcode() const;
int answer_count() const;
// Returns an iterator to the resource records in the answer section. Must be
// called after InitParse. The iterator is valid only in the scope of the
// DnsResponse.
DnsRecordParser Parser() const;
private:
// Convenience for header access.
const dns_protocol::Header* header() const;
// Buffer into which response bytes are read.
scoped_refptr<IOBufferWithSize> io_buffer_;
// Iterator constructed after InitParse positioned at the answer section.
DnsRecordParser parser_;
DISALLOW_COPY_AND_ASSIGN(DnsResponse);
};
} // namespace net
#endif // NET_DNS_DNS_RESPONSE_H_
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