net: add DnsRRResovler to fetch arbitary DNS resource types.

net/base/dns_util.h

 // Copyright (c) 2009 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_BASE_DNS_UTIL_H_
 #define NET_BASE_DNS_UTIL_H_
 #pragma once
 
 #include <string>
 
+#include "base/basictypes.h"
+
 namespace net {
 
 // DNSDomainFromDot - convert a domain string to DNS format. From DJB's
 // public domain DNS library.
 //
 //   dotted: a string in dotted form: "www.google.com"
 //   out: a result in DNS form: "\x03www\x06google\x03com\x00"
 bool DNSDomainFromDot(const std::string& dotted, std::string* out);
 
 // Returns true iff the given character is in the set of valid DNS label
 // characters as given in RFC 3490, 4.1, 3(a)
 bool IsSTD3ASCIIValidCharacter(char c);
 
 // Returns the hostname by trimming the ending dot, if one exists.
 std::string TrimEndingDot(const std::string& host);
 
+// DNS resource record types. See
+// http://www.iana.org/assignments/dns-parameters
+
+static const uint16 kDNS_TXT = 16;
+static const uint16 kDNS_RRSIG = 46;
+static const uint16 kDNS_CERT = 37;
+static const uint16 kDNS_ANY = 0xff;
+
 }  // namespace net
 
 #endif  // NET_BASE_DNS_UTIL_H_