1 #ifndef __NET_NSH_H 2 #define __NET_NSH_H 1 3 4 #include <linux/skbuff.h> 5 6 /* 7 * Network Service Header: 8 * 0 1 2 3 9 * 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 10 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 11 * |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | 12 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 13 * | Service Path Identifier (SPI) | Service Index | 14 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 15 * | | 16 * ~ Mandatory/Optional Context Headers ~ 17 * | | 18 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 19 * 20 * Version: The version field is used to ensure backward compatibility 21 * going forward with future NSH specification updates. It MUST be set 22 * to 0x0 by the sender, in this first revision of NSH. Given the 23 * widespread implementation of existing hardware that uses the first 24 * nibble after an MPLS label stack for ECMP decision processing, this 25 * document reserves version 01b and this value MUST NOT be used in 26 * future versions of the protocol. Please see [RFC7325] for further 27 * discussion of MPLS-related forwarding requirements. 28 * 29 * O bit: Setting this bit indicates an Operations, Administration, and 30 * Maintenance (OAM) packet. The actual format and processing of SFC 31 * OAM packets is outside the scope of this specification (see for 32 * example [I-D.ietf-sfc-oam-framework] for one approach). 33 * 34 * The O bit MUST be set for OAM packets and MUST NOT be set for non-OAM 35 * packets. The O bit MUST NOT be modified along the SFP. 36 * 37 * SF/SFF/SFC Proxy/Classifier implementations that do not support SFC 38 * OAM procedures SHOULD discard packets with O bit set, but MAY support 39 * a configurable parameter to enable forwarding received SFC OAM 40 * packets unmodified to the next element in the chain. Forwarding OAM 41 * packets unmodified by SFC elements that do not support SFC OAM 42 * procedures may be acceptable for a subset of OAM functions, but can 43 * result in unexpected outcomes for others, thus it is recommended to 44 * analyze the impact of forwarding an OAM packet for all OAM functions 45 * prior to enabling this behavior. The configurable parameter MUST be 46 * disabled by default. 47 * 48 * TTL: Indicates the maximum SFF hops for an SFP. This field is used 49 * for service plane loop detection. The initial TTL value SHOULD be 50 * configurable via the control plane; the configured initial value can 51 * be specific to one or more SFPs. If no initial value is explicitly 52 * provided, the default initial TTL value of 63 MUST be used. Each SFF 53 * involved in forwarding an NSH packet MUST decrement the TTL value by 54 * 1 prior to NSH forwarding lookup. Decrementing by 1 from an incoming 55 * value of 0 shall result in a TTL value of 63. The packet MUST NOT be 56 * forwarded if TTL is, after decrement, 0. 57 * 58 * All other flag fields, marked U, are unassigned and available for 59 * future use, see Section 11.2.1. Unassigned bits MUST be set to zero 60 * upon origination, and MUST be ignored and preserved unmodified by 61 * other NSH supporting elements. Elements which do not understand the 62 * meaning of any of these bits MUST NOT modify their actions based on 63 * those unknown bits. 64 * 65 * Length: The total length, in 4-byte words, of NSH including the Base 66 * Header, the Service Path Header, the Fixed Length Context Header or 67 * Variable Length Context Header(s). The length MUST be 0x6 for MD 68 * Type equal to 0x1, and MUST be 0x2 or greater for MD Type equal to 69 * 0x2. The length of the NSH header MUST be an integer multiple of 4 70 * bytes, thus variable length metadata is always padded out to a 71 * multiple of 4 bytes. 72 * 73 * MD Type: Indicates the format of NSH beyond the mandatory Base Header 74 * and the Service Path Header. MD Type defines the format of the 75 * metadata being carried. 76 * 77 * 0x0 - This is a reserved value. Implementations SHOULD silently 78 * discard packets with MD Type 0x0. 79 * 80 * 0x1 - This indicates that the format of the header includes a fixed 81 * length Context Header (see Figure 4 below). 82 * 83 * 0x2 - This does not mandate any headers beyond the Base Header and 84 * Service Path Header, but may contain optional variable length Context 85 * Header(s). The semantics of the variable length Context Header(s) 86 * are not defined in this document. The format of the optional 87 * variable length Context Headers is provided in Section 2.5.1. 88 * 89 * 0xF - This value is reserved for experimentation and testing, as per 90 * [RFC3692]. Implementations not explicitly configured to be part of 91 * an experiment SHOULD silently discard packets with MD Type 0xF. 92 * 93 * Next Protocol: indicates the protocol type of the encapsulated data. 94 * NSH does not alter the inner payload, and the semantics on the inner 95 * protocol remain unchanged due to NSH service function chaining. 96 * Please see the IANA Considerations section below, Section 11.2.5. 97 * 98 * This document defines the following Next Protocol values: 99 * 100 * 0x1: IPv4 101 * 0x2: IPv6 102 * 0x3: Ethernet 103 * 0x4: NSH 104 * 0x5: MPLS 105 * 0xFE: Experiment 1 106 * 0xFF: Experiment 2 107 * 108 * Packets with Next Protocol values not supported SHOULD be silently 109 * dropped by default, although an implementation MAY provide a 110 * configuration parameter to forward them. Additionally, an 111 * implementation not explicitly configured for a specific experiment 112 * [RFC3692] SHOULD silently drop packets with Next Protocol values 0xFE 113 * and 0xFF. 114 * 115 * Service Path Identifier (SPI): Identifies a service path. 116 * Participating nodes MUST use this identifier for Service Function 117 * Path selection. The initial classifier MUST set the appropriate SPI 118 * for a given classification result. 119 * 120 * Service Index (SI): Provides location within the SFP. The initial 121 * classifier for a given SFP SHOULD set the SI to 255, however the 122 * control plane MAY configure the initial value of SI as appropriate 123 * (i.e., taking into account the length of the service function path). 124 * The Service Index MUST be decremented by a value of 1 by Service 125 * Functions or by SFC Proxy nodes after performing required services 126 * and the new decremented SI value MUST be used in the egress packet's 127 * NSH. The initial Classifier MUST send the packet to the first SFF in 128 * the identified SFP for forwarding along an SFP. If re-classification 129 * occurs, and that re-classification results in a new SPI, the 130 * (re)classifier is, in effect, the initial classifier for the 131 * resultant SPI. 132 * 133 * The SI is used in conjunction the with Service Path Identifier for 134 * Service Function Path Selection and for determining the next SFF/SF 135 * in the path. The SI is also valuable when troubleshooting or 136 * reporting service paths. Additionally, while the TTL field is the 137 * main mechanism for service plane loop detection, the SI can also be 138 * used for detecting service plane loops. 139 * 140 * When the Base Header specifies MD Type = 0x1, a Fixed Length Context 141 * Header (16-bytes) MUST be present immediately following the Service 142 * Path Header. The value of a Fixed Length Context 143 * Header that carries no metadata MUST be set to zero. 144 * 145 * When the base header specifies MD Type = 0x2, zero or more Variable 146 * Length Context Headers MAY be added, immediately following the 147 * Service Path Header (see Figure 5). Therefore, Length = 0x2, 148 * indicates that only the Base Header followed by the Service Path 149 * Header are present. The optional Variable Length Context Headers 150 * MUST be of an integer number of 4-bytes. The base header Length 151 * field MUST be used to determine the offset to locate the original 152 * packet or frame for SFC nodes that require access to that 153 * information. 154 * 155 * The format of the optional variable length Context Headers 156 * 157 * 0 1 2 3 158 * 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 1 159 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 * | Metadata Class | Type |U| Length | 161 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 * | Variable Metadata | 163 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 * 165 * Metadata Class (MD Class): Defines the scope of the 'Type' field to 166 * provide a hierarchical namespace. The IANA Considerations 167 * Section 11.2.4 defines how the MD Class values can be allocated to 168 * standards bodies, vendors, and others. 169 * 170 * Type: Indicates the explicit type of metadata being carried. The 171 * definition of the Type is the responsibility of the MD Class owner. 172 * 173 * Unassigned bit: One unassigned bit is available for future use. This 174 * bit MUST NOT be set, and MUST be ignored on receipt. 175 * 176 * Length: Indicates the length of the variable metadata, in bytes. In 177 * case the metadata length is not an integer number of 4-byte words, 178 * the sender MUST add pad bytes immediately following the last metadata 179 * byte to extend the metadata to an integer number of 4-byte words. 180 * The receiver MUST round up the length field to the nearest 4-byte 181 * word boundary, to locate and process the next field in the packet. 182 * The receiver MUST access only those bytes in the metadata indicated 183 * by the length field (i.e., actual number of bytes) and MUST ignore 184 * the remaining bytes up to the nearest 4-byte word boundary. The 185 * Length may be 0 or greater. 186 * 187 * A value of 0 denotes a Context Header without a Variable Metadata 188 * field. 189 * 190 * [0] https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh/ 191 */ 192 193 /** 194 * struct nsh_md1_ctx - Keeps track of NSH context data 195 * @nshc<1-4>: NSH Contexts. 196 */ 197 struct nsh_md1_ctx { 198 __be32 context[4]; 199 }; 200 201 struct nsh_md2_tlv { 202 __be16 md_class; 203 u8 type; 204 u8 length; 205 u8 md_value[]; 206 }; 207 208 struct nshhdr { 209 __be16 ver_flags_ttl_len; 210 u8 mdtype; 211 u8 np; 212 __be32 path_hdr; 213 union { 214 struct nsh_md1_ctx md1; 215 struct nsh_md2_tlv md2; 216 }; 217 }; 218 219 /* Masking NSH header fields. */ 220 #define NSH_VER_MASK 0xc000 221 #define NSH_VER_SHIFT 14 222 #define NSH_FLAGS_MASK 0x3000 223 #define NSH_FLAGS_SHIFT 12 224 #define NSH_TTL_MASK 0x0fc0 225 #define NSH_TTL_SHIFT 6 226 #define NSH_LEN_MASK 0x003f 227 #define NSH_LEN_SHIFT 0 228 229 #define NSH_MDTYPE_MASK 0x0f 230 #define NSH_MDTYPE_SHIFT 0 231 232 #define NSH_SPI_MASK 0xffffff00 233 #define NSH_SPI_SHIFT 8 234 #define NSH_SI_MASK 0x000000ff 235 #define NSH_SI_SHIFT 0 236 237 /* MD Type Registry. */ 238 #define NSH_M_TYPE1 0x01 239 #define NSH_M_TYPE2 0x02 240 #define NSH_M_EXP1 0xFE 241 #define NSH_M_EXP2 0xFF 242 243 /* NSH Base Header Length */ 244 #define NSH_BASE_HDR_LEN 8 245 246 /* NSH MD Type 1 header Length. */ 247 #define NSH_M_TYPE1_LEN 24 248 249 /* NSH header maximum Length. */ 250 #define NSH_HDR_MAX_LEN 256 251 252 /* NSH context headers maximum Length. */ 253 #define NSH_CTX_HDRS_MAX_LEN 248 254 255 static inline struct nshhdr *nsh_hdr(struct sk_buff *skb) 256 { 257 return (struct nshhdr *)skb_network_header(skb); 258 } 259 260 static inline u16 nsh_hdr_len(const struct nshhdr *nsh) 261 { 262 return ((ntohs(nsh->ver_flags_ttl_len) & NSH_LEN_MASK) 263 >> NSH_LEN_SHIFT) << 2; 264 } 265 266 static inline u8 nsh_get_ver(const struct nshhdr *nsh) 267 { 268 return (ntohs(nsh->ver_flags_ttl_len) & NSH_VER_MASK) 269 >> NSH_VER_SHIFT; 270 } 271 272 static inline u8 nsh_get_flags(const struct nshhdr *nsh) 273 { 274 return (ntohs(nsh->ver_flags_ttl_len) & NSH_FLAGS_MASK) 275 >> NSH_FLAGS_SHIFT; 276 } 277 278 static inline u8 nsh_get_ttl(const struct nshhdr *nsh) 279 { 280 return (ntohs(nsh->ver_flags_ttl_len) & NSH_TTL_MASK) 281 >> NSH_TTL_SHIFT; 282 } 283 284 static inline void __nsh_set_xflag(struct nshhdr *nsh, u16 xflag, u16 xmask) 285 { 286 nsh->ver_flags_ttl_len 287 = (nsh->ver_flags_ttl_len & ~htons(xmask)) | htons(xflag); 288 } 289 290 static inline void nsh_set_flags_and_ttl(struct nshhdr *nsh, u8 flags, u8 ttl) 291 { 292 __nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) | 293 ((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK), 294 NSH_FLAGS_MASK | NSH_TTL_MASK); 295 } 296 297 static inline void nsh_set_flags_ttl_len(struct nshhdr *nsh, u8 flags, 298 u8 ttl, u8 len) 299 { 300 len = len >> 2; 301 __nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) | 302 ((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK) | 303 ((len << NSH_LEN_SHIFT) & NSH_LEN_MASK), 304 NSH_FLAGS_MASK | NSH_TTL_MASK | NSH_LEN_MASK); 305 } 306 307 int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh); 308 int nsh_pop(struct sk_buff *skb); 309 310 #endif /* __NET_NSH_H */ 311