diff options
Diffstat (limited to 'include/net/nsh.h')
| -rw-r--r-- | include/net/nsh.h | 310 |
1 files changed, 310 insertions, 0 deletions
diff --git a/include/net/nsh.h b/include/net/nsh.h new file mode 100644 index 000000000..350b1ad11 --- /dev/null +++ b/include/net/nsh.h @@ -0,0 +1,310 @@ +#ifndef __NET_NSH_H +#define __NET_NSH_H 1 + +#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 + * @nshc<1-4>: NSH Contexts. + */ +struct nsh_md1_ctx { + __be32 context[4]; +}; + +struct nsh_md2_tlv { + __be16 md_class; + u8 type; + u8 length; + u8 md_value[]; +}; + +struct nshhdr { + __be16 ver_flags_ttl_len; + u8 mdtype; + u8 np; + __be32 path_hdr; + union { + struct nsh_md1_ctx md1; + struct nsh_md2_tlv md2; + }; +}; + +/* Masking NSH header fields. */ +#define NSH_VER_MASK 0xc000 +#define NSH_VER_SHIFT 14 +#define NSH_FLAGS_MASK 0x3000 +#define NSH_FLAGS_SHIFT 12 +#define NSH_TTL_MASK 0x0fc0 +#define NSH_TTL_SHIFT 6 +#define NSH_LEN_MASK 0x003f +#define NSH_LEN_SHIFT 0 + +#define NSH_MDTYPE_MASK 0x0f +#define NSH_MDTYPE_SHIFT 0 + +#define NSH_SPI_MASK 0xffffff00 +#define NSH_SPI_SHIFT 8 +#define NSH_SI_MASK 0x000000ff +#define NSH_SI_SHIFT 0 + +/* MD Type Registry. */ +#define NSH_M_TYPE1 0x01 +#define NSH_M_TYPE2 0x02 +#define NSH_M_EXP1 0xFE +#define NSH_M_EXP2 0xFF + +/* NSH Base Header Length */ +#define NSH_BASE_HDR_LEN 8 + +/* NSH MD Type 1 header Length. */ +#define NSH_M_TYPE1_LEN 24 + +/* NSH header maximum Length. */ +#define NSH_HDR_MAX_LEN 256 + +/* NSH context headers maximum Length. */ +#define NSH_CTX_HDRS_MAX_LEN 248 + +static inline struct nshhdr *nsh_hdr(struct sk_buff *skb) +{ + return (struct nshhdr *)skb_network_header(skb); +} + +static inline u16 nsh_hdr_len(const struct nshhdr *nsh) +{ + return ((ntohs(nsh->ver_flags_ttl_len) & NSH_LEN_MASK) + >> NSH_LEN_SHIFT) << 2; +} + +static inline u8 nsh_get_ver(const struct nshhdr *nsh) +{ + return (ntohs(nsh->ver_flags_ttl_len) & NSH_VER_MASK) + >> NSH_VER_SHIFT; +} + +static inline u8 nsh_get_flags(const struct nshhdr *nsh) +{ + return (ntohs(nsh->ver_flags_ttl_len) & NSH_FLAGS_MASK) + >> NSH_FLAGS_SHIFT; +} + +static inline u8 nsh_get_ttl(const struct nshhdr *nsh) +{ + return (ntohs(nsh->ver_flags_ttl_len) & NSH_TTL_MASK) + >> NSH_TTL_SHIFT; +} + +static inline void __nsh_set_xflag(struct nshhdr *nsh, u16 xflag, u16 xmask) +{ + nsh->ver_flags_ttl_len + = (nsh->ver_flags_ttl_len & ~htons(xmask)) | htons(xflag); +} + +static inline void nsh_set_flags_and_ttl(struct nshhdr *nsh, u8 flags, u8 ttl) +{ + __nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) | + ((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK), + NSH_FLAGS_MASK | NSH_TTL_MASK); +} + +static inline void nsh_set_flags_ttl_len(struct nshhdr *nsh, u8 flags, + u8 ttl, u8 len) +{ + len = len >> 2; + __nsh_set_xflag(nsh, ((flags << NSH_FLAGS_SHIFT) & NSH_FLAGS_MASK) | + ((ttl << NSH_TTL_SHIFT) & NSH_TTL_MASK) | + ((len << NSH_LEN_SHIFT) & NSH_LEN_MASK), + NSH_FLAGS_MASK | NSH_TTL_MASK | NSH_LEN_MASK); +} + +int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh); +int nsh_pop(struct sk_buff *skb); + +#endif /* __NET_NSH_H */ |