Multicast DNS implementation (initial)

net/dns/dns_protocol.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_PROTOCOL_H_
 #define NET_DNS_DNS_PROTOCOL_H_
 
 #include "base/basictypes.h"
 #include "net/base/net_export.h"
 
 namespace net {
 
 namespace dns_protocol {
 
 static const uint16 kDefaultPort = 53;
+static const uint16 kDefaultPortMulticast = 5353;
 
 // 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                       |
 //  +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
@@ skipping 68 matching lines @@
 // "cache-flush bit", as described in http://www.rfc-editor.org/rfc/rfc6762.txt
 // section 10.2.
 static const uint16 kMDnsClassMask = 0x7FFF;
 
 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;
 
+// RFC 6762, section 17: Messages over the local link are restricted by the
+// medium's MTU, and must be under 9000 bytes
+static const int kMaxMulticastSize = 9000;
+
 // 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 kTypePTR = 12;
 static const uint16 kTypeTXT = 16;
 static const uint16 kTypeAAAA = 28;
@@ skipping 13 matching lines @@
 static const uint16 kFlagRA = 0x80;
 static const uint16 kFlagRD = 0x100;
 static const uint16 kFlagTC = 0x200;
 static const uint16 kFlagAA = 0x400;
 
 }  // namespace dns_protocol
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_PROTOCOL_H_