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net: add NSH header structures and helpers
NSH (Network Service Header)[1] is a new protocol for service function chaining, it can be handled as a L3 protocol like IPv4 and IPv6, Eth + NSH + Inner packet or VxLAN-gpe + NSH + Inner packet are two typical use cases. This patch adds NSH header structures and helpers for NSH GSO support and Open vSwitch NSH support. [1] https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh/ [Jiri: added nsh_hdr() helper and renamed the header struct to "struct nshhdr" to match the usual pattern. Removed packet type defines, these are now shared with VXLAN-GPE.] Signed-off-by: Yi Yang <[email protected]> Signed-off-by: Jiri Benc <[email protected]> Signed-off-by: David S. Miller <[email protected]>
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| #ifndef __NET_NSH_H | ||
| #define __NET_NSH_H 1 | ||
|
|
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| #include <linux/skbuff.h> | ||
|
|
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| /* | ||
| * 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 | ||
|
|
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| static inline struct nshhdr *nsh_hdr(struct sk_buff *skb) | ||
| { | ||
| return (struct nshhdr *)skb_network_header(skb); | ||
| } | ||
|
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| static inline u16 nsh_hdr_len(const struct nshhdr *nsh) | ||
| { | ||
| return ((ntohs(nsh->ver_flags_ttl_len) & NSH_LEN_MASK) | ||
| >> NSH_LEN_SHIFT) << 2; | ||
| } | ||
|
|
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| 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; | ||
| } | ||
|
|
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| static inline u8 nsh_get_ttl(const struct nshhdr *nsh) | ||
| { | ||
| return (ntohs(nsh->ver_flags_ttl_len) & NSH_TTL_MASK) | ||
| >> NSH_TTL_SHIFT; | ||
| } | ||
|
|
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| 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); | ||
| } | ||
|
|
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| 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); | ||
| } | ||
|
|
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| 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); | ||
| } | ||
|
|
||
| #endif /* __NET_NSH_H */ |