include/net/nsh.h

   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 */