Isolates generic DnsClient from AsyncHostResolver.

net/dns/dns_protocol.h

Index: net/dns/dns_protocol.h
diff --git a/net/dns/dns_protocol.h b/net/dns/dns_protocol.h
new file mode 100644
index 0000000000000000000000000000000000000000..494429bde1dfc288e600046364f0b540728a7754
--- /dev/null
+++ b/net/dns/dns_protocol.h
@@ -0,0 +1,122 @@
+// Copyright (c) 2011 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_PROTOCOL_H_
+#define NET_DNS_DNS_PROTOCOL_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+namespace dns_protocol {
+
+// DNS packet consists of a header followed by questions and/or answers.
+// For the meaning of specific fields, please see RFC 1035 and 2535
+
+// Header format.
+//                                  1  1  1  1  1  1
+//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      ID                       |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |QR|   Opcode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    QDCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ANCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    NSCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                    ARCOUNT                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+// Question format.
+//                                  1  1  1  1  1  1
+//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                                               |
+//  /                     QNAME                     /
+//  /                                               /
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     QTYPE                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     QCLASS                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+// Answer format.
+//                                  1  1  1  1  1  1
+//    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                                               |
+//  /                                               /
+//  /                      NAME                     /
+//  |                                               |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      TYPE                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                     CLASS                     |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                      TTL                      |
+//  |                                               |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+//  |                   RDLENGTH                    |
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
+//  /                     RDATA                     /
+//  /                                               /
+//  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
+
+#pragma pack(push)
+#pragma pack(1)
+
+// On-the-wire header. All uint16 are in network order.
+// Used internally in DnsQuery and DnsResponseParser.
+struct NET_EXPORT_PRIVATE Header {
+  uint16 id;
+  uint8 flags[2];
+  uint16 qdcount;
+  uint16 ancount;
+  uint16 nscount;
+  uint16 arcount;
+};
+
+#pragma pack(pop)
+
+static const uint8 kLabelMask = 0xc0;
+static const uint8 kLabelPointer = 0xc0;
+static const uint8 kLabelDirect = 0x0;
+static const uint16 kOffsetMask = 0x3fff;
+
+static const int kMaxNameLength = 255;
+
+// RFC 1035, section 4.2.1: Messages carried by UDP are restricted to 512
+// bytes (not counting the IP nor UDP headers).
+static const int kMaxUDPSize = 512;
+
+// DNS class types.
+static const uint16 kClassIN = 1;
+
+// DNS resource record types. See
+// http://www.iana.org/assignments/dns-parameters
+static const uint16 kTypeA = 1;
+static const uint16 kTypeCNAME = 5;
+static const uint16 kTypeTXT = 16;
+static const uint16 kTypeAAAA = 28;
+
+// DNS rcode values.
+static const uint8 kRcodeMask = 0xf;
+static const uint8 kRcodeNOERROR = 0;
+static const uint8 kRcodeFORMERR = 1;
+static const uint8 kRcodeSERVFAIL = 2;
+static const uint8 kRcodeNXDOMAIN = 3;
+static const uint8 kRcodeNOTIMP = 4;
+static const uint8 kRcodeREFUSED = 5;
+
+}  // namespace dns_protocol
+
+}  // namespace net
+
+#endif  // NET_DNS_DNS_PROTOCOL_H_
+