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+/*
+ * Copyright (c) 2015 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef included_nsh_packet_h
+#define included_nsh_packet_h
+
+/*
+ * NSH packet format from draft-quinn-sfc-nsh-03.txt
+ *
+ * NSH Base Header
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *  |Ver|O|C|    TTL    |   Length  |    MD Type    | Next Protocol |
+ *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * 
+ * 
+ * Base Header Field Descriptions:
+ * 
+ * Version: The version field is used to ensure backward compatibility
+ * going forward with future NSH updates.
+ * 
+ * O bit: Indicates that this packet is an operations and management
+ * (OAM) packet.  SFF and SFs nodes MUST examine the payload and take
+ * appropriate action (e.g. return status information).
+ * 
+ * OAM message specifics and handling details are outside the scope of
+ * this document.
+ * 
+ * C bit: Indicates that a critical metadata TLV is present (see section
+ * 7).  This bit acts as an indication for hardware implementers to
+ * decide how to handle the presence of a critical TLV without
+ * necessarily needing to parse all TLVs present.  The C bit MUST be set
+ * to 1 if one or more critical TLVs are present.
+ * 
+ * All other flag fields are reserved.
+ * 
+ * Length: total length, in 4 byte words, of the NSH header, including
+ * optional variable TLVs.  Length must be equal or greater than 6.
+ * 
+ * MD Type: indicates the format of NSH beyond the base header and the
+ * type of metadata being carried.  This typing is used to describe the
+ * use for the metadata.  A new registry will be requested from IANA for
+ * the MD Type.  NSH defines one type, type = 0x1 which indicates that
+ * the format of the header is as per this draft.
+ * 
+ * The format of the base header is invariant, and not described by MD
+ * Type.
+ * 
+ * Next Protocol: indicates the protocol type of the original packet.  A
+ * new IANA registry will be created for protocol type.
+ * 
+ * This draft defines the following Next Protocol values:
+ * 
+ * 0x1 : IPv4
+ * 0x2 : IPv6
+ * 0x3 : Ethernet
+ */
+
+typedef CLIB_PACKED(struct {
+  u8 ver_o_c; //TTL: high 4 bit
+  u8 length;  //TTL: low 2 bit
+  u8 md_type;
+  u8 next_protocol;
+  u32 nsp_nsi; // nsp 24 bits, nsi 8 bits
+}) nsh_base_header_t;
+
+typedef CLIB_PACKED(struct {
+  /* Context headers, always present */
+  u32 c1;
+  u32 c2;
+  u32 c3;
+  u32 c4;
+}) nsh_md1_data_t;
+
+typedef CLIB_PACKED(struct {
+  u16 class;
+  u8 type;
+  u8 length;
+}) nsh_tlv_header_t;
+
+typedef nsh_tlv_header_t nsh_md2_data_t;
+
+typedef CLIB_PACKED(struct {
+  nsh_base_header_t nsh_base;
+  union {
+     nsh_md1_data_t md1_data;
+     nsh_md2_data_t md2_data;
+   } md;
+}) nsh_header_t;
+
+#define NSH_VERSION (0<<6)
+#define NSH_O_BIT (1<<5)
+#define NSH_C_BIT (1<<4)
+
+#define NSH_TTL_H4_MASK 0xF
+#define NSH_TTL_L2_MASK 0xC0
+#define NSH_LEN_MASK 0x3F
+
+/* Network byte order shift / mask */
+#define NSH_NSI_MASK 0xFF
+#define NSH_NSP_MASK (0x00FFFFFF)
+#define NSH_NSP_SHIFT 8
+
+#endif /* included_nsh_packet_h */