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Side by Side Diff: net/dns/dns_response.h

Issue 992733002: Remove //net (except for Android test stuff) and sdch (Closed) Base URL: git@github.com:domokit/mojo.git@master
Patch Set: Created 5 years, 9 months ago
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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 #ifndef NET_DNS_DNS_RESPONSE_H_
6 #define NET_DNS_DNS_RESPONSE_H_
7
8 #include <string>
9
10 #include "base/basictypes.h"
11 #include "base/memory/ref_counted.h"
12 #include "base/strings/string_piece.h"
13 #include "base/time/time.h"
14 #include "net/base/net_export.h"
15 #include "net/base/net_util.h"
16
17 namespace net {
18
19 class AddressList;
20 class DnsQuery;
21 class IOBufferWithSize;
22
23 namespace dns_protocol {
24 struct Header;
25 }
26
27 // Parsed resource record.
28 struct NET_EXPORT_PRIVATE DnsResourceRecord {
29 DnsResourceRecord();
30 ~DnsResourceRecord();
31
32 std::string name; // in dotted form
33 uint16 type;
34 uint16 klass;
35 uint32 ttl;
36 base::StringPiece rdata; // points to the original response buffer
37 };
38
39 // Iterator to walk over resource records of the DNS response packet.
40 class NET_EXPORT_PRIVATE DnsRecordParser {
41 public:
42 // Construct an uninitialized iterator.
43 DnsRecordParser();
44
45 // Construct an iterator to process the |packet| of given |length|.
46 // |offset| points to the beginning of the answer section.
47 DnsRecordParser(const void* packet, size_t length, size_t offset);
48
49 // Returns |true| if initialized.
50 bool IsValid() const { return packet_ != NULL; }
51
52 // Returns |true| if no more bytes remain in the packet.
53 bool AtEnd() const { return cur_ == packet_ + length_; }
54
55 // Returns current offset into the packet.
56 size_t GetOffset() const { return cur_ - packet_; }
57
58 // Parses a (possibly compressed) DNS name from the packet starting at
59 // |pos|. Stores output (even partial) in |out| unless |out| is NULL. |out|
60 // is stored in the dotted form, e.g., "example.com". Returns number of bytes
61 // consumed or 0 on failure.
62 // This is exposed to allow parsing compressed names within RRDATA for TYPEs
63 // such as NS, CNAME, PTR, MX, SOA.
64 // See RFC 1035 section 4.1.4.
65 unsigned ReadName(const void* pos, std::string* out) const;
66
67 // Parses the next resource record into |record|. Returns true if succeeded.
68 bool ReadRecord(DnsResourceRecord* record);
69
70 // Skip a question section, returns true if succeeded.
71 bool SkipQuestion();
72
73 private:
74 const char* packet_;
75 size_t length_;
76 // Current offset within the packet.
77 const char* cur_;
78 };
79
80 // Buffer-holder for the DNS response allowing easy access to the header fields
81 // and resource records. After reading into |io_buffer| must call InitParse to
82 // position the RR parser.
83 class NET_EXPORT_PRIVATE DnsResponse {
84 public:
85 // Possible results from ParseToAddressList.
86 enum Result {
87 DNS_PARSE_OK = 0,
88 DNS_MALFORMED_RESPONSE, // DnsRecordParser failed before the end of
89 // packet.
90 DNS_MALFORMED_CNAME, // Could not parse CNAME out of RRDATA.
91 DNS_NAME_MISMATCH, // Got an address but no ordered chain of CNAMEs
92 // leads there.
93 DNS_SIZE_MISMATCH, // Got an address but size does not match.
94 DNS_CNAME_AFTER_ADDRESS, // Found CNAME after an address record.
95 DNS_ADDRESS_TTL_MISMATCH, // OBSOLETE. No longer used.
96 DNS_NO_ADDRESSES, // OBSOLETE. No longer used.
97 // Only add new values here.
98 DNS_PARSE_RESULT_MAX, // Bounding value for histograms.
99 };
100
101 // Constructs a response buffer large enough to store one byte more than
102 // largest possible response, to detect malformed responses.
103 DnsResponse();
104
105 // Constructs a response buffer of given length. Used for TCP transactions.
106 explicit DnsResponse(size_t length);
107
108 // Constructs a response from |data|. Used for testing purposes only!
109 DnsResponse(const void* data, size_t length, size_t answer_offset);
110
111 ~DnsResponse();
112
113 // Internal buffer accessor into which actual bytes of response will be
114 // read.
115 IOBufferWithSize* io_buffer() { return io_buffer_.get(); }
116
117 // Assuming the internal buffer holds |nbytes| bytes, returns true iff the
118 // packet matches the |query| id and question.
119 bool InitParse(int nbytes, const DnsQuery& query);
120
121 // Assuming the internal buffer holds |nbytes| bytes, initialize the parser
122 // without matching it against an existing query.
123 bool InitParseWithoutQuery(int nbytes);
124
125 // Returns true if response is valid, that is, after successful InitParse.
126 bool IsValid() const;
127
128 // All of the methods below are valid only if the response is valid.
129
130 // Accessors for the header.
131 uint16 flags() const; // excluding rcode
132 uint8 rcode() const;
133
134 unsigned answer_count() const;
135 unsigned additional_answer_count() const;
136
137 // Accessors to the question. The qname is unparsed.
138 base::StringPiece qname() const;
139 uint16 qtype() const;
140
141 // Returns qname in dotted format.
142 std::string GetDottedName() const;
143
144 // Returns an iterator to the resource records in the answer section.
145 // The iterator is valid only in the scope of the DnsResponse.
146 // This operation is idempotent.
147 DnsRecordParser Parser() const;
148
149 // Extracts an AddressList from this response. Returns SUCCESS if succeeded.
150 // Otherwise returns a detailed error number.
151 Result ParseToAddressList(AddressList* addr_list, base::TimeDelta* ttl) const;
152
153 private:
154 // Convenience for header access.
155 const dns_protocol::Header* header() const;
156
157 // Buffer into which response bytes are read.
158 scoped_refptr<IOBufferWithSize> io_buffer_;
159
160 // Iterator constructed after InitParse positioned at the answer section.
161 // It is never updated afterwards, so can be used in accessors.
162 DnsRecordParser parser_;
163
164 DISALLOW_COPY_AND_ASSIGN(DnsResponse);
165 };
166
167 } // namespace net
168
169 #endif // NET_DNS_DNS_RESPONSE_H_
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