[net] HostResolverImpl + DnsTransaction + DnsConfigService = Asynchronous DNS ready for experiments.

net/dns/dns_response.h

 // 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_
 #pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/string_piece.h"
+#include "base/time.h"
 #include "net/base/net_export.h"
 #include "net/base/net_util.h"
 
 namespace net {
 
+class AddressList;
 class DnsQuery;
 class IOBufferWithSize;
 
 namespace dns_protocol {
 struct Header;
 }
 
 // Parsed resource record.
 struct NET_EXPORT_PRIVATE DnsResourceRecord {
   DnsResourceRecord();
@@ skipping 25 matching lines @@
   // 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.
-  int ParseName(const void* pos, std::string* out) const;
+  unsigned ReadName(const void* pos, std::string* out) const;
 
-  // Parses the next resource record. Returns true if succeeded.
-  bool ParseRecord(DnsResourceRecord* record);
+  // Parses the next resource record into |record|. Returns true if succeeded.
+  bool ReadRecord(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:
+  // Possible results from ParseToAddressList
+  enum Result {
+    DNS_SUCCESS = 0,
+    DNS_MALFORMED_RESPONSE,    // DnsRecordParser failed before the end of
+                               // packet.
+    DNS_MALFORMED_CNAME,       // Could not parse CNAME out of RRDATA.
+    DNS_NAME_MISMATCH,         // Got an address but no ordered chain of CNAMEs
+                               // leads there.
+    DNS_SIZE_MISMATCH,         // Got an address but size does not match.
+    DNS_CNAME_AFTER_ADDRESS,   // Found CNAME after an address record.
+    DNS_ADDRESS_TTL_MISMATCH,  // TTL of all address records are not identical.
+    DNS_NO_ADDRESSES,          // No address records found.
+  };
+
   // 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);
 
   // Returns true if response is valid, that is, after successful InitParse.
   bool IsValid() const;
 
   // All of the methods below are valid only if the response is valid.
 
   // Accessors for the header.
   uint16 flags() const;  // excluding rcode
   uint8 rcode() const;
-  int answer_count() const;
+  unsigned answer_count() const;
 
   // Accessors to the question. The qname is unparsed.
   base::StringPiece qname() const;
   uint16 qtype() const;
 
   // Returns qname in dotted format.
   std::string GetDottedName() 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;
 
+  // Extracts an AddressList from this response. Returns SUCCESS if succeeded.
+  // Otherwise returns a detailed error number.
+  Result ParseToAddressList(AddressList* addr_list, base::TimeDelta* ttl) 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.
   // It is never updated afterwards, so can be used in accessors.
   DnsRecordParser parser_;
 
   DISALLOW_COPY_AND_ASSIGN(DnsResponse);
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_RESPONSE_H_