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net: add NSH header structures and helpers

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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 <yi.y.yang@intel.com>
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yi Yang 2017-08-28 21:43:23 +02:00 committed by David S. Miller
parent fa20e0e32c
commit 1f0b7744c5
1 changed files with 307 additions and 0 deletions
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307
include/net/nsh.h Normal file
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#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);
}
#endif /* __NET_NSH_H */