#ifndef __NET_NSH_H #define __NET_NSH_H … #include <linux/skbuff.h> /* * Network Service 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|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | Service Path Identifier (SPI) | Service Index | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | | * ~ Mandatory/Optional Context Headers ~ * | | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * * Version: The version field is used to ensure backward compatibility * going forward with future NSH specification updates. It MUST be set * to 0x0 by the sender, in this first revision of NSH. Given the * widespread implementation of existing hardware that uses the first * nibble after an MPLS label stack for ECMP decision processing, this * document reserves version 01b and this value MUST NOT be used in * future versions of the protocol. Please see [RFC7325] for further * discussion of MPLS-related forwarding requirements. * * O bit: Setting this bit indicates an Operations, Administration, and * Maintenance (OAM) packet. The actual format and processing of SFC * OAM packets is outside the scope of this specification (see for * example [I-D.ietf-sfc-oam-framework] for one approach). * * The O bit MUST be set for OAM packets and MUST NOT be set for non-OAM * packets. The O bit MUST NOT be modified along the SFP. * * SF/SFF/SFC Proxy/Classifier implementations that do not support SFC * OAM procedures SHOULD discard packets with O bit set, but MAY support * a configurable parameter to enable forwarding received SFC OAM * packets unmodified to the next element in the chain. Forwarding OAM * packets unmodified by SFC elements that do not support SFC OAM * procedures may be acceptable for a subset of OAM functions, but can * result in unexpected outcomes for others, thus it is recommended to * analyze the impact of forwarding an OAM packet for all OAM functions * prior to enabling this behavior. The configurable parameter MUST be * disabled by default. * * TTL: Indicates the maximum SFF hops for an SFP. This field is used * for service plane loop detection. The initial TTL value SHOULD be * configurable via the control plane; the configured initial value can * be specific to one or more SFPs. If no initial value is explicitly * provided, the default initial TTL value of 63 MUST be used. Each SFF * involved in forwarding an NSH packet MUST decrement the TTL value by * 1 prior to NSH forwarding lookup. Decrementing by 1 from an incoming * value of 0 shall result in a TTL value of 63. The packet MUST NOT be * forwarded if TTL is, after decrement, 0. * * All other flag fields, marked U, are unassigned and available for * future use, see Section 11.2.1. Unassigned bits MUST be set to zero * upon origination, and MUST be ignored and preserved unmodified by * other NSH supporting elements. Elements which do not understand the * meaning of any of these bits MUST NOT modify their actions based on * those unknown bits. * * Length: The total length, in 4-byte words, of NSH including the Base * Header, the Service Path Header, the Fixed Length Context Header or * Variable Length Context Header(s). The length MUST be 0x6 for MD * Type equal to 0x1, and MUST be 0x2 or greater for MD Type equal to * 0x2. The length of the NSH header MUST be an integer multiple of 4 * bytes, thus variable length metadata is always padded out to a * multiple of 4 bytes. * * MD Type: Indicates the format of NSH beyond the mandatory Base Header * and the Service Path Header. MD Type defines the format of the * metadata being carried. * * 0x0 - This is a reserved value. Implementations SHOULD silently * discard packets with MD Type 0x0. * * 0x1 - This indicates that the format of the header includes a fixed * length Context Header (see Figure 4 below). * * 0x2 - This does not mandate any headers beyond the Base Header and * Service Path Header, but may contain optional variable length Context * Header(s). The semantics of the variable length Context Header(s) * are not defined in this document. The format of the optional * variable length Context Headers is provided in Section 2.5.1. * * 0xF - This value is reserved for experimentation and testing, as per * [RFC3692]. Implementations not explicitly configured to be part of * an experiment SHOULD silently discard packets with MD Type 0xF. * * Next Protocol: indicates the protocol type of the encapsulated data. * NSH does not alter the inner payload, and the semantics on the inner * protocol remain unchanged due to NSH service function chaining. * Please see the IANA Considerations section below, Section 11.2.5. * * This document defines the following Next Protocol values: * * 0x1: IPv4 * 0x2: IPv6 * 0x3: Ethernet * 0x4: NSH * 0x5: MPLS * 0xFE: Experiment 1 * 0xFF: Experiment 2 * * Packets with Next Protocol values not supported SHOULD be silently * dropped by default, although an implementation MAY provide a * configuration parameter to forward them. Additionally, an * implementation not explicitly configured for a specific experiment * [RFC3692] SHOULD silently drop packets with Next Protocol values 0xFE * and 0xFF. * * Service Path Identifier (SPI): Identifies a service path. * Participating nodes MUST use this identifier for Service Function * Path selection. The initial classifier MUST set the appropriate SPI * for a given classification result. * * Service Index (SI): Provides location within the SFP. The initial * classifier for a given SFP SHOULD set the SI to 255, however the * control plane MAY configure the initial value of SI as appropriate * (i.e., taking into account the length of the service function path). * The Service Index MUST be decremented by a value of 1 by Service * Functions or by SFC Proxy nodes after performing required services * and the new decremented SI value MUST be used in the egress packet's * NSH. The initial Classifier MUST send the packet to the first SFF in * the identified SFP for forwarding along an SFP. If re-classification * occurs, and that re-classification results in a new SPI, the * (re)classifier is, in effect, the initial classifier for the * resultant SPI. * * The SI is used in conjunction the with Service Path Identifier for * Service Function Path Selection and for determining the next SFF/SF * in the path. The SI is also valuable when troubleshooting or * reporting service paths. Additionally, while the TTL field is the * main mechanism for service plane loop detection, the SI can also be * used for detecting service plane loops. * * When the Base Header specifies MD Type = 0x1, a Fixed Length Context * Header (16-bytes) MUST be present immediately following the Service * Path Header. The value of a Fixed Length Context * Header that carries no metadata MUST be set to zero. * * When the base header specifies MD Type = 0x2, zero or more Variable * Length Context Headers MAY be added, immediately following the * Service Path Header (see Figure 5). Therefore, Length = 0x2, * indicates that only the Base Header followed by the Service Path * Header are present. The optional Variable Length Context Headers * MUST be of an integer number of 4-bytes. The base header Length * field MUST be used to determine the offset to locate the original * packet or frame for SFC nodes that require access to that * information. * * The format of the optional variable length Context Headers * * 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 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | Metadata Class | Type |U| Length | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * | Variable Metadata | * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * * Metadata Class (MD Class): Defines the scope of the 'Type' field to * provide a hierarchical namespace. The IANA Considerations * Section 11.2.4 defines how the MD Class values can be allocated to * standards bodies, vendors, and others. * * Type: Indicates the explicit type of metadata being carried. The * definition of the Type is the responsibility of the MD Class owner. * * Unassigned bit: One unassigned bit is available for future use. This * bit MUST NOT be set, and MUST be ignored on receipt. * * Length: Indicates the length of the variable metadata, in bytes. In * case the metadata length is not an integer number of 4-byte words, * the sender MUST add pad bytes immediately following the last metadata * byte to extend the metadata to an integer number of 4-byte words. * The receiver MUST round up the length field to the nearest 4-byte * word boundary, to locate and process the next field in the packet. * The receiver MUST access only those bytes in the metadata indicated * by the length field (i.e., actual number of bytes) and MUST ignore * the remaining bytes up to the nearest 4-byte word boundary. The * Length may be 0 or greater. * * A value of 0 denotes a Context Header without a Variable Metadata * field. * * [0] https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh/ */ /** * struct nsh_md1_ctx - Keeps track of NSH context data * @context: NSH Contexts. */ struct nsh_md1_ctx { … }; struct nsh_md2_tlv { … }; struct nshhdr { … }; /* Masking NSH header fields. */ #define NSH_VER_MASK … #define NSH_VER_SHIFT … #define NSH_FLAGS_MASK … #define NSH_FLAGS_SHIFT … #define NSH_TTL_MASK … #define NSH_TTL_SHIFT … #define NSH_LEN_MASK … #define NSH_LEN_SHIFT … #define NSH_MDTYPE_MASK … #define NSH_MDTYPE_SHIFT … #define NSH_SPI_MASK … #define NSH_SPI_SHIFT … #define NSH_SI_MASK … #define NSH_SI_SHIFT … /* MD Type Registry. */ #define NSH_M_TYPE1 … #define NSH_M_TYPE2 … #define NSH_M_EXP1 … #define NSH_M_EXP2 … /* NSH Base Header Length */ #define NSH_BASE_HDR_LEN … /* NSH MD Type 1 header Length. */ #define NSH_M_TYPE1_LEN … /* NSH header maximum Length. */ #define NSH_HDR_MAX_LEN … /* NSH context headers maximum Length. */ #define NSH_CTX_HDRS_MAX_LEN … static inline struct nshhdr *nsh_hdr(struct sk_buff *skb) { … } static inline u16 nsh_hdr_len(const struct nshhdr *nsh) { … } static inline u8 nsh_get_ver(const struct nshhdr *nsh) { … } static inline u8 nsh_get_flags(const struct nshhdr *nsh) { … } static inline u8 nsh_get_ttl(const struct nshhdr *nsh) { … } static inline void __nsh_set_xflag(struct nshhdr *nsh, u16 xflag, u16 xmask) { … } static inline void nsh_set_flags_and_ttl(struct nshhdr *nsh, u8 flags, u8 ttl) { … } static inline void nsh_set_flags_ttl_len(struct nshhdr *nsh, u8 flags, u8 ttl, u8 len) { … } int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh); int nsh_pop(struct sk_buff *skb); #endif /* __NET_NSH_H */
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