Cache for mDNS records

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"
 
@@ skipping 72 matching lines @@
   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;
 
+// In MDns the most significant bit of the rrclass is designated as the
+// "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;
 
 // DNS class types.
 static const uint16 kClassIN = 1;
 
 // DNS resource record types. See
@@ skipping 19 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_
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