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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.
- #ifndef NET_DNS_DNS_RESPONSE_H_
- #define NET_DNS_DNS_RESPONSE_H_
- #include <stddef.h>
- #include <stdint.h>
- #include <string>
- #include <vector>
- #include "base/memory/ref_counted.h"
- #include "base/strings/string_piece.h"
- #include "net/base/net_export.h"
- #include "net/dns/dns_response_result_extractor.h"
- #include "net/dns/public/dns_protocol.h"
- #include "third_party/abseil-cpp/absl/types/optional.h"
- namespace base {
- class BigEndianWriter;
- } // namespace base
- namespace net {
- class DnsQuery;
- class IOBuffer;
- namespace dns_protocol {
- struct Header;
- } // namespace dns_protocol
- // Structure representing a Resource Record as specified in RFC 1035, Section
- // 4.1.3.
- struct NET_EXPORT_PRIVATE DnsResourceRecord {
- DnsResourceRecord();
- DnsResourceRecord(const DnsResourceRecord& other);
- DnsResourceRecord(DnsResourceRecord&& other);
- ~DnsResourceRecord();
- DnsResourceRecord& operator=(const DnsResourceRecord& other);
- DnsResourceRecord& operator=(DnsResourceRecord&& other);
- // A helper to set |owned_rdata| that also sets |rdata| to point to it. The
- // |value| must be non-empty. See the definition of |owned_rdata| below.
- void SetOwnedRdata(std::string value);
- // NAME (variable length) + TYPE (2 bytes) + CLASS (2 bytes) + TTL (4 bytes) +
- // RDLENGTH (2 bytes) + RDATA (variable length)
- //
- // Uses |owned_rdata| for RDATA if non-empty.
- size_t CalculateRecordSize() const;
- std::string name; // in dotted form
- uint16_t type = 0;
- uint16_t klass = 0;
- uint32_t ttl = 0;
- // Points to the original response buffer or otherwise to |owned_rdata|.
- base::StringPiece rdata;
- // Used to construct a DnsResponse from data. This field is empty if |rdata|
- // points to the response buffer.
- std::string owned_rdata;
- };
- // 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. `ReadRecord()` will
- // fail if called more than `num_records` times, no matter whether or not
- // there is additional data at the end of the buffer that may appear to be a
- // valid record.
- DnsRecordParser(const void* packet,
- size_t length,
- size_t offset,
- size_t num_records);
- // Returns |true| if initialized.
- bool IsValid() const { return packet_ != nullptr; }
- // Returns |true| if no more bytes remain in the packet.
- bool AtEnd() const { return cur_ == packet_ + length_; }
- // Returns current offset into the packet.
- size_t GetOffset() const { return cur_ - packet_; }
- // 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.
- unsigned ReadName(const void* pos, std::string* out) const;
- // Parses the next resource record into |record|. Returns true if succeeded.
- bool ReadRecord(DnsResourceRecord* record);
- // Read a question section, returns true if succeeded. In `DnsResponse`,
- // expected to be called during parse, after which the current offset will be
- // after all questions.
- bool ReadQuestion(std::string& out_dotted_qname, uint16_t& out_qtype);
- private:
- const char* packet_ = nullptr;
- size_t length_ = 0;
- size_t num_records_ = 0;
- size_t num_records_parsed_ = 0;
- // Current offset within the packet.
- const char* cur_ = nullptr;
- };
- // 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 a response buffer large enough to store one byte more than
- // largest possible response, to detect malformed responses.
- DnsResponse();
- // Constructs a response message from `answers` and the originating `query`.
- // After the successful construction, and the parser is also initialized.
- //
- // If `validate_records` is false, DCHECKs validating the correctness of
- // records will be skipped. Intended for tests to allow creation of malformed
- // responses.
- DnsResponse(uint16_t id,
- bool is_authoritative,
- const std::vector<DnsResourceRecord>& answers,
- const std::vector<DnsResourceRecord>& authority_records,
- const std::vector<DnsResourceRecord>& additional_records,
- const absl::optional<DnsQuery>& query,
- uint8_t rcode = dns_protocol::kRcodeNOERROR,
- bool validate_records = true);
- // Constructs a response buffer of given length. Used for TCP transactions.
- explicit DnsResponse(size_t length);
- // Constructs a response from the passed buffer.
- DnsResponse(scoped_refptr<IOBuffer> buffer, size_t size);
- // Constructs a response from |data|. Used for testing purposes only!
- DnsResponse(const void* data, size_t length, size_t answer_offset);
- static DnsResponse CreateEmptyNoDataResponse(uint16_t id,
- bool is_authoritative,
- base::StringPiece qname,
- uint16_t qtype);
- // Move-only.
- DnsResponse(DnsResponse&& other);
- DnsResponse& operator=(DnsResponse&& other);
- ~DnsResponse();
- // Internal buffer accessor into which actual bytes of response will be
- // read.
- IOBuffer* io_buffer() { return io_buffer_.get(); }
- const IOBuffer* io_buffer() const { return io_buffer_.get(); }
- // Size of the internal buffer.
- size_t io_buffer_size() const { return io_buffer_size_; }
- // Assuming the internal buffer holds |nbytes| bytes, returns true iff the
- // packet matches the |query| id and question. This should only be called if
- // the response is constructed from a raw buffer.
- bool InitParse(size_t nbytes, const DnsQuery& query);
- // Assuming the internal buffer holds |nbytes| bytes, initialize the parser
- // without matching it against an existing query. This should only be called
- // if the response is constructed from a raw buffer.
- bool InitParseWithoutQuery(size_t nbytes);
- // Does not require the response to be fully parsed and valid, but will return
- // nullopt if the ID is unknown. The ID will only be known if the response is
- // successfully constructed from data or if InitParse...() has been able to
- // parse at least as far as the ID (not necessarily a fully successful parse).
- absl::optional<uint16_t> id() const;
- // Returns true if response is valid, that is, after successful InitParse, or
- // after successful construction of a new response from data.
- bool IsValid() const;
- // All of the methods below are valid only if the response is valid.
- // Accessors for the header.
- uint16_t flags() const; // excluding rcode
- uint8_t rcode() const;
- unsigned question_count() const;
- unsigned answer_count() const;
- unsigned authority_count() const;
- unsigned additional_answer_count() const;
- const std::vector<uint16_t>& qtypes() const {
- DCHECK(parser_.IsValid());
- DCHECK_EQ(question_count(), qtypes_.size());
- return qtypes_;
- }
- const std::vector<std::string>& dotted_qnames() const {
- DCHECK(parser_.IsValid());
- DCHECK_EQ(question_count(), dotted_qnames_.size());
- return dotted_qnames_;
- }
- // Shortcuts to get qtype or qname for single-query responses. Should only be
- // used in cases where there is known to be exactly one question (e.g. because
- // that has been validated by `InitParse()`).
- uint16_t GetSingleQType() const;
- base::StringPiece GetSingleDottedName() const;
- // Returns an iterator to the resource records in the answer section.
- // The iterator is valid only in the scope of the DnsResponse.
- // This operation is idempotent.
- DnsRecordParser Parser() const;
- private:
- bool WriteHeader(base::BigEndianWriter* writer,
- const dns_protocol::Header& header);
- bool WriteQuestion(base::BigEndianWriter* writer, const DnsQuery& query);
- bool WriteRecord(base::BigEndianWriter* writer,
- const DnsResourceRecord& record,
- bool validate_record);
- bool WriteAnswer(base::BigEndianWriter* writer,
- const DnsResourceRecord& answer,
- const absl::optional<DnsQuery>& query,
- bool validate_record);
- // Convenience for header access.
- const dns_protocol::Header* header() const;
- // Buffer into which response bytes are read.
- scoped_refptr<IOBuffer> io_buffer_;
- // Size of the buffer.
- size_t io_buffer_size_;
- // Iterator constructed after InitParse positioned at the answer section.
- // It is never updated afterwards, so can be used in accessors.
- DnsRecordParser parser_;
- bool id_available_ = false;
- std::vector<std::string> dotted_qnames_;
- std::vector<uint16_t> qtypes_;
- };
- } // namespace net
- #endif // NET_DNS_DNS_RESPONSE_H_
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