1 // Copyright (c) 2011 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_QUERY_H_
6 #define NET_DNS_DNS_QUERY_H_
7 
8 #include <stddef.h>
9 #include <stdint.h>
10 
11 #include <memory>
12 #include <string>
13 
14 #include "base/macros.h"
15 #include "base/memory/ref_counted.h"
16 #include "base/strings/string_piece.h"
17 #include "net/base/net_export.h"
18 
19 namespace base {
20 class BigEndianReader;
21 }  // namespace base
22 
23 namespace net {
24 
25 class OptRecordRdata;
26 
27 namespace dns_protocol {
28 struct Header;
29 }  // namespace dns_protocol
30 
31 class IOBufferWithSize;
32 
33 // Represents on-the-wire DNS query message as an object.
34 class NET_EXPORT_PRIVATE DnsQuery {
35  public:
36   enum class PaddingStrategy {
37     // Query will not be padded. Recommended strategy when query will not be
38     // encrypted.
39     NONE,
40 
41     // Query will be padded to the next multiple of 128 octets. Recommended
42     // strategy (per RFC 8467) when query will be encrypted, e.g. through
43     // DNS-over-HTTPS.
44     BLOCK_LENGTH_128,
45   };
46 
47   // Constructs a query message from |qname| which *MUST* be in a valid
48   // DNS name format, and |qtype|. The qclass is set to IN.
49   // If |opt_rdata| is not null, an OPT record will be added to the "Additional"
50   // section of the query.
51   DnsQuery(uint16_t id,
52            const base::StringPiece& qname,
53            uint16_t qtype,
54            const OptRecordRdata* opt_rdata = nullptr,
55            PaddingStrategy padding_strategy = PaddingStrategy::NONE);
56 
57   // Constructs an empty query from a raw packet in |buffer|. If the raw packet
58   // represents a valid DNS query in the wire format (RFC 1035), Parse() will
59   // populate the empty query.
60   explicit DnsQuery(scoped_refptr<IOBufferWithSize> buffer);
61 
62   // Copies are constructed with an independent cloned, not mirrored, buffer.
63   DnsQuery(const DnsQuery& query);
64   DnsQuery& operator=(const DnsQuery& query);
65 
66   ~DnsQuery();
67 
68   // Clones |this| verbatim, with ID field of the header set to |id|.
69   std::unique_ptr<DnsQuery> CloneWithNewId(uint16_t id) const;
70 
71   // Returns true and populates the query if the internally stored raw packet
72   // can be parsed. This should only be called when DnsQuery is constructed from
73   // the raw buffer.
74   // |valid_bytes| indicates the number of initialized bytes in the raw buffer.
75   // E.g. if the buffer holds a packet received from the network, the buffer may
76   // be allocated with the maximum size of a UDP packet, but |valid_bytes|
77   // indicates the number of bytes actually received from the network. If the
78   // parsing requires reading more than the number of initialized bytes, this
79   // method fails and returns false.
80   bool Parse(size_t valid_bytes);
81 
82   // DnsQuery field accessors.
83   uint16_t id() const;
84   base::StringPiece qname() const;
85   uint16_t qtype() const;
86 
87   // Returns the Question section of the query.  Used when matching the
88   // response.
89   base::StringPiece question() const;
90 
91   // Returns the size of the question section.
92   size_t question_size() const;
93 
94   // IOBuffer accessor to be used for writing out the query. The buffer has
95   // the same byte layout as the DNS query wire format.
io_buffer()96   IOBufferWithSize* io_buffer() const { return io_buffer_.get(); }
97 
98   void set_flags(uint16_t flags);
99 
100  private:
101   DnsQuery(const DnsQuery& orig, uint16_t id);
102   void CopyFrom(const DnsQuery& orig);
103 
104   bool ReadHeader(base::BigEndianReader* reader, dns_protocol::Header* out);
105   // After read, |out| is in the DNS format, e.g.
106   // "\x03""www""\x08""chromium""\x03""com""\x00". Use DNSDomainToString to
107   // convert to the dotted format "www.chromium.com" with no trailing dot.
108   bool ReadName(base::BigEndianReader* reader, std::string* out);
109 
110   // Size of the DNS name (*NOT* hostname) we are trying to resolve; used
111   // to calculate offsets.
112   size_t qname_size_ = 0;
113 
114   // Contains query bytes to be consumed by higher level Write() call.
115   scoped_refptr<IOBufferWithSize> io_buffer_;
116 
117   // Pointer to the dns header section.
118   dns_protocol::Header* header_ = nullptr;
119 };
120 
121 }  // namespace net
122 
123 #endif  // NET_DNS_DNS_QUERY_H_
124