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/* SPDX-License-Identifier: GPL-2.0 */
* Management Component Transport Protocol (MCTP)
* Copyright (c) 2021 Code Construct
* Copyright (c) 2021 Google
#ifndef __NET_MCTP_H
#define __NET_MCTP_H
#include <linux/bits.h>
#include <linux/mctp.h>
#include <linux/netdevice.h>
#include <net/net_namespace.h>
#include <net/sock.h>
/* MCTP packet definitions */
struct mctp_hdr {
u8 ver;
u8 dest;
u8 src;
u8 flags_seq_tag;
#define MCTP_VER_MIN 1
#define MCTP_VER_MAX 1
/* Definitions for flags_seq_tag field */
static inline bool mctp_address_ok(mctp_eid_t eid)
return eid >= 8 && eid < 255;
static inline struct mctp_hdr *mctp_hdr(struct sk_buff *skb)
return (struct mctp_hdr *)skb_network_header(skb);
/* socket implementation */
struct mctp_sock {
struct sock sk;
/* bind() params */
unsigned int bind_net;
mctp_eid_t bind_addr;
__u8 bind_type;
/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
bool addr_ext;
/* list of mctp_sk_key, for incoming tag lookup. updates protected
* by sk->net->keys_lock
struct hlist_head keys;
/* mechanism for expiring allocated keys; will release an allocated
* tag, and any netdev state for a request/response pairing
struct timer_list key_expiry;
/* Key for matching incoming packets to sockets or reassembly contexts.
* Packets are matched on (src,dest,tag).
* Lifetime / locking requirements:
* - individual key data (ie, the struct itself) is protected by key->lock;
* changes must be made with that lock held.
* - the lookup fields: peer_addr, local_addr and tag are set before the
* key is added to lookup lists, and never updated.
* - A ref to the key must be held (throuh key->refs) if a pointer to the
* key is to be accessed after key->lock is released.
* - a mctp_sk_key contains a reference to a struct sock; this is valid
* for the life of the key. On sock destruction (through unhash), the key is
* removed from lists (see below), and marked invalid.
* - these mctp_sk_keys appear on two lists:
* 1) the struct mctp_sock->keys list
* 2) the struct netns_mctp->keys list
* presences on these lists requires a (single) refcount to be held; both
* lists are updated as a single operation.
* Updates and lookups in either list are performed under the
* netns_mctp->keys lock. Lookup functions will need to lock the key and
* take a reference before unlocking the keys_lock. Consequently, the list's
* keys_lock *cannot* be acquired with the individual key->lock held.
* - a key may have a sk_buff attached as part of an in-progress message
* reassembly (->reasm_head). The reasm data is protected by the individual
* key->lock.
* - there are two destruction paths for a mctp_sk_key:
* - through socket unhash (see mctp_sk_unhash). This performs the list
* removal under keys_lock.
* - where a key is established to receive a reply message: after receiving
* the (complete) reply, or during reassembly errors. Here, we clean up
* the reassembly context (marking reasm_dead, to prevent another from
* starting), and remove the socket from the netns & socket lists.
* - through an expiry timeout, on a per-socket timer
struct mctp_sk_key {
mctp_eid_t peer_addr;
mctp_eid_t local_addr;
__u8 tag; /* incoming tag match; invert TO for local */
/* we hold a ref to sk when set */
struct sock *sk;
/* routing lookup list */
struct hlist_node hlist;
/* per-socket list */
struct hlist_node sklist;
/* lock protects against concurrent updates to the reassembly and
* expiry data below.
spinlock_t lock;
/* Keys are referenced during the output path, which may sleep */
refcount_t refs;
/* incoming fragment reassembly context */
struct sk_buff *reasm_head;
struct sk_buff **reasm_tailp;
bool reasm_dead;
u8 last_seq;
/* key validity */
bool valid;
/* expiry timeout; valid (above) cleared on expiry */
unsigned long expiry;
/* free to use for device flow state tracking. Initialised to
* zero on initial key creation
unsigned long dev_flow_state;
struct mctp_dev *dev;
struct mctp_skb_cb {
unsigned int magic;
unsigned int net;
int ifindex; /* extended/direct addressing if set */
mctp_eid_t src;
unsigned char halen;
unsigned char haddr[MAX_ADDR_LEN];
/* skb control-block accessors with a little extra debugging for initial
* development.
* TODO: remove checks & mctp_skb_cb->magic; replace callers of __mctp_cb
* with mctp_cb().
* __mctp_cb() is only for the initial ingress code; we should see ->magic set
* at all times after this.
static inline struct mctp_skb_cb *__mctp_cb(struct sk_buff *skb)
struct mctp_skb_cb *cb = (void *)skb->cb;
cb->magic = 0x4d435450;
return cb;
static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
struct mctp_skb_cb *cb = (void *)skb->cb;
BUILD_BUG_ON(sizeof(struct mctp_skb_cb) > sizeof(skb->cb));
WARN_ON(cb->magic != 0x4d435450);
return (void *)(skb->cb);
/* If CONFIG_MCTP_FLOWS, we may add one of these as a SKB extension,
* indicating the flow to the device driver.
struct mctp_flow {
struct mctp_sk_key *key;
/* Route definition.
* These are held in the pernet->mctp.routes list, with RCU protection for
* removed routes. We hold a reference to the netdev; routes need to be
* dropped on NETDEV_UNREGISTER events.
* Updates to the route table are performed under rtnl; all reads under RCU,
* so routes cannot be referenced over a RCU grace period. Specifically: A
* caller cannot block between mctp_route_lookup and mctp_route_release()
struct mctp_route {
mctp_eid_t min, max;
struct mctp_dev *dev;
unsigned int mtu;
unsigned char type;
int (*output)(struct mctp_route *route,
struct sk_buff *skb);
struct list_head list;
refcount_t refs;
struct rcu_head rcu;
/* route interfaces */
struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
mctp_eid_t daddr);
int mctp_local_output(struct sock *sk, struct mctp_route *rt,
struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag);
void mctp_key_unref(struct mctp_sk_key *key);
/* routing <--> device interface */
unsigned int mctp_default_net(struct net *net);
int mctp_default_net_set(struct net *net, unsigned int index);
int mctp_route_add_local(struct mctp_dev *mdev, mctp_eid_t addr);
int mctp_route_remove_local(struct mctp_dev *mdev, mctp_eid_t addr);
void mctp_route_remove_dev(struct mctp_dev *mdev);
/* neighbour definitions */
enum mctp_neigh_source {
struct mctp_neigh {
struct mctp_dev *dev;
mctp_eid_t eid;
enum mctp_neigh_source source;
unsigned char ha[MAX_ADDR_LEN];
struct list_head list;
struct rcu_head rcu;
int mctp_neigh_init(void);
void mctp_neigh_exit(void);
// ret_hwaddr may be NULL, otherwise must have space for MAX_ADDR_LEN
int mctp_neigh_lookup(struct mctp_dev *dev, mctp_eid_t eid,
void *ret_hwaddr);
void mctp_neigh_remove_dev(struct mctp_dev *mdev);
int mctp_routes_init(void);
void mctp_routes_exit(void);
void mctp_device_init(void);
void mctp_device_exit(void);
#endif /* __NET_MCTP_H */