mctp.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * Management Component Transport Protocol (MCTP)
  4 *
  5 * Copyright (c) 2021 Code Construct
  6 * Copyright (c) 2021 Google
  7 */
  8
  9#ifndef __NET_MCTP_H
 10#define __NET_MCTP_H
 11
 12#include <linux/bits.h>
 13#include <linux/mctp.h>
 14#include <linux/netdevice.h>
 15#include <net/net_namespace.h>
 16#include <net/sock.h>
 17
 18/* MCTP packet definitions */
 19struct mctp_hdr {
 20	u8	ver;
 21	u8	dest;
 22	u8	src;
 23	u8	flags_seq_tag;
 24};
 25
 26#define MCTP_VER_MIN	1
 27#define MCTP_VER_MAX	1
 28
 29/* Definitions for flags_seq_tag field */
 30#define MCTP_HDR_FLAG_SOM	BIT(7)
 31#define MCTP_HDR_FLAG_EOM	BIT(6)
 32#define MCTP_HDR_FLAG_TO	BIT(3)
 33#define MCTP_HDR_FLAGS		GENMASK(5, 3)
 34#define MCTP_HDR_SEQ_SHIFT	4
 35#define MCTP_HDR_SEQ_MASK	GENMASK(1, 0)
 36#define MCTP_HDR_TAG_SHIFT	0
 37#define MCTP_HDR_TAG_MASK	GENMASK(2, 0)
 38
 39#define MCTP_INITIAL_DEFAULT_NET	1
 40
 41static inline bool mctp_address_unicast(mctp_eid_t eid)
 42{
 43	return eid >= 8 && eid < 255;
 44}
 45
 46static inline bool mctp_address_broadcast(mctp_eid_t eid)
 47{
 48	return eid == 255;
 49}
 50
 51static inline bool mctp_address_null(mctp_eid_t eid)
 52{
 53	return eid == 0;
 54}
 55
 56static inline bool mctp_address_matches(mctp_eid_t match, mctp_eid_t eid)
 57{
 58	return match == eid || match == MCTP_ADDR_ANY;
 59}
 60
 61static inline struct mctp_hdr *mctp_hdr(struct sk_buff *skb)
 62{
 63	return (struct mctp_hdr *)skb_network_header(skb);
 64}
 65
 66/* socket implementation */
 67struct mctp_sock {
 68	struct sock	sk;
 69
 70	/* bind() params */
 71	unsigned int	bind_net;
 72	mctp_eid_t	bind_local_addr;
 73	mctp_eid_t	bind_peer_addr;
 74	unsigned int	bind_peer_net;
 75	bool		bind_peer_set;
 76	__u8		bind_type;
 77
 78	/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
 79	bool		addr_ext;
 80
 81	/* list of mctp_sk_key, for incoming tag lookup. updates protected
 82	 * by sk->net->keys_lock
 83	 */
 84	struct hlist_head keys;
 85
 86	/* mechanism for expiring allocated keys; will release an allocated
 87	 * tag, and any netdev state for a request/response pairing
 88	 */
 89	struct timer_list key_expiry;
 90};
 91
 92/* Key for matching incoming packets to sockets or reassembly contexts.
 93 * Packets are matched on (peer EID, local EID, tag).
 94 *
 95 * Lifetime / locking requirements:
 96 *
 97 *  - individual key data (ie, the struct itself) is protected by key->lock;
 98 *    changes must be made with that lock held.
 99 *
100 *  - the lookup fields: peer_addr, local_addr and tag are set before the
101 *    key is added to lookup lists, and never updated.
102 *
103 *  - A ref to the key must be held (throuh key->refs) if a pointer to the
104 *    key is to be accessed after key->lock is released.
105 *
106 *  - a mctp_sk_key contains a reference to a struct sock; this is valid
107 *    for the life of the key. On sock destruction (through unhash), the key is
108 *    removed from lists (see below), and marked invalid.
109 *
110 * - these mctp_sk_keys appear on two lists:
111 *     1) the struct mctp_sock->keys list
112 *     2) the struct netns_mctp->keys list
113 *
114 *   presences on these lists requires a (single) refcount to be held; both
115 *   lists are updated as a single operation.
116 *
117 *   Updates and lookups in either list are performed under the
118 *   netns_mctp->keys lock. Lookup functions will need to lock the key and
119 *   take a reference before unlocking the keys_lock. Consequently, the list's
120 *   keys_lock *cannot* be acquired with the individual key->lock held.
121 *
122 * - a key may have a sk_buff attached as part of an in-progress message
123 *   reassembly (->reasm_head). The reasm data is protected by the individual
124 *   key->lock.
125 *
126 * - there are two destruction paths for a mctp_sk_key:
127 *
128 *    - through socket unhash (see mctp_sk_unhash). This performs the list
129 *      removal under keys_lock.
130 *
131 *    - where a key is established to receive a reply message: after receiving
132 *      the (complete) reply, or during reassembly errors. Here, we clean up
133 *      the reassembly context (marking reasm_dead, to prevent another from
134 *      starting), and remove the socket from the netns & socket lists.
135 *
136 *    - through an expiry timeout, on a per-socket timer
137 */
138struct mctp_sk_key {
139	unsigned int	net;
140	mctp_eid_t	peer_addr;
141	mctp_eid_t	local_addr; /* MCTP_ADDR_ANY for local owned tags */
142	__u8		tag; /* incoming tag match; invert TO for local */
143
144	/* we hold a ref to sk when set */
145	struct sock	*sk;
146
147	/* routing lookup list */
148	struct hlist_node hlist;
149
150	/* per-socket list */
151	struct hlist_node sklist;
152
153	/* lock protects against concurrent updates to the reassembly and
154	 * expiry data below.
155	 */
156	spinlock_t	lock;
157
158	/* Keys are referenced during the output path, which may sleep */
159	refcount_t	refs;
160
161	/* incoming fragment reassembly context */
162	struct sk_buff	*reasm_head;
163	struct sk_buff	**reasm_tailp;
164	bool		reasm_dead;
165	u8		last_seq;
166
167	/* key validity */
168	bool		valid;
169
170	/* expiry timeout; valid (above) cleared on expiry */
171	unsigned long	expiry;
172
173	/* free to use for device flow state tracking. Initialised to
174	 * zero on initial key creation
175	 */
176	unsigned long	dev_flow_state;
177	struct mctp_dev	*dev;
178
179	/* a tag allocated with SIOCMCTPALLOCTAG ioctl will not expire
180	 * automatically on timeout or response, instead SIOCMCTPDROPTAG
181	 * is used.
182	 */
183	bool		manual_alloc;
184};
185
186struct mctp_skb_cb {
187	unsigned int	magic;
188	unsigned int	net;
189	/* fields below provide extended addressing for ingress to recvmsg() */
190	int		ifindex;
191	unsigned char	halen;
192	unsigned char	haddr[MAX_ADDR_LEN];
193};
194
195/* skb control-block accessors with a little extra debugging for initial
196 * development.
197 *
198 * TODO: remove checks & mctp_skb_cb->magic; replace callers of __mctp_cb
199 * with mctp_cb().
200 *
201 * __mctp_cb() is only for the initial ingress code; we should see ->magic set
202 * at all times after this.
203 */
204static inline struct mctp_skb_cb *__mctp_cb(struct sk_buff *skb)
205{
206	struct mctp_skb_cb *cb = (void *)skb->cb;
207
208	cb->magic = 0x4d435450;
209	return cb;
210}
211
212static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
213{
214	struct mctp_skb_cb *cb = (void *)skb->cb;
215
216	BUILD_BUG_ON(sizeof(struct mctp_skb_cb) > sizeof(skb->cb));
217	WARN_ON(cb->magic != 0x4d435450);
218	return cb;
219}
220
221/* If CONFIG_MCTP_FLOWS, we may add one of these as a SKB extension,
222 * indicating the flow to the device driver.
223 */
224struct mctp_flow {
225	struct mctp_sk_key *key;
226};
227
228struct mctp_dst;
229
230/* Route definition.
231 *
232 * These are held in the pernet->mctp.routes list, with RCU protection for
233 * removed routes. We hold a reference to the netdev; routes need to be
234 * dropped on NETDEV_UNREGISTER events.
235 *
236 * Updates to the route table are performed under rtnl; all reads under RCU,
237 * so routes cannot be referenced over a RCU grace period.
238 */
239struct mctp_route {
240	mctp_eid_t		min, max;
241
242	unsigned char		type;
243
244	unsigned int		mtu;
245
246	enum {
247		MCTP_ROUTE_DIRECT,
248		MCTP_ROUTE_GATEWAY,
249	} dst_type;
250	union {
251		struct mctp_dev	*dev;
252		struct mctp_fq_addr gateway;
253	};
254
255	int			(*output)(struct mctp_dst *dst,
256					  struct sk_buff *skb);
257
258	struct list_head	list;
259	refcount_t		refs;
260	struct rcu_head		rcu;
261};
262
263/* Route lookup result: dst. Represents the results of a routing decision,
264 * but is only held over the individual routing operation.
265 *
266 * Will typically be stored on the caller stack, and must be released after
267 * usage.
268 */
269struct mctp_dst {
270	struct mctp_dev *dev;
271	unsigned int mtu;
272	mctp_eid_t nexthop;
273
274	/* set for direct addressing */
275	unsigned char halen;
276	unsigned char haddr[MAX_ADDR_LEN];
277
278	int (*output)(struct mctp_dst *dst, struct sk_buff *skb);
279};
280
281int mctp_dst_from_extaddr(struct mctp_dst *dst, struct net *net, int ifindex,
282			  unsigned char halen, const unsigned char *haddr);
283
284/* route interfaces */
285int mctp_route_lookup(struct net *net, unsigned int dnet,
286		      mctp_eid_t daddr, struct mctp_dst *dst);
287
288void mctp_dst_release(struct mctp_dst *dst);
289
290/* always takes ownership of skb */
291int mctp_local_output(struct sock *sk, struct mctp_dst *dst,
292		      struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag);
293
294void mctp_key_unref(struct mctp_sk_key *key);
295struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
296					 unsigned int netid,
297					 mctp_eid_t local, mctp_eid_t peer,
298					 bool manual, u8 *tagp);
299
300/* routing <--> device interface */
301unsigned int mctp_default_net(struct net *net);
302int mctp_default_net_set(struct net *net, unsigned int index);
303int mctp_route_add_local(struct mctp_dev *mdev, mctp_eid_t addr);
304int mctp_route_remove_local(struct mctp_dev *mdev, mctp_eid_t addr);
305void mctp_route_remove_dev(struct mctp_dev *mdev);
306
307/* neighbour definitions */
308enum mctp_neigh_source {
309	MCTP_NEIGH_STATIC,
310	MCTP_NEIGH_DISCOVER,
311};
312
313struct mctp_neigh {
314	struct mctp_dev		*dev;
315	mctp_eid_t		eid;
316	enum mctp_neigh_source	source;
317
318	unsigned char		ha[MAX_ADDR_LEN];
319
320	struct list_head	list;
321	struct rcu_head		rcu;
322};
323
324int mctp_neigh_init(void);
325void mctp_neigh_exit(void);
326
327// ret_hwaddr may be NULL, otherwise must have space for MAX_ADDR_LEN
328int mctp_neigh_lookup(struct mctp_dev *dev, mctp_eid_t eid,
329		      void *ret_hwaddr);
330void mctp_neigh_remove_dev(struct mctp_dev *mdev);
331
332int mctp_routes_init(void);
333void mctp_routes_exit(void);
334
335int mctp_device_init(void);
336void mctp_device_exit(void);
337
338/* MCTP IDs and Codes from DMTF specification
339 * "DSP0239 Management Component Transport Protocol (MCTP) IDs and Codes"
340 * https://www.dmtf.org/sites/default/files/standards/documents/DSP0239_1.11.1.pdf
341 */
342enum mctp_phys_binding {
343	MCTP_PHYS_BINDING_UNSPEC	= 0x00,
344	MCTP_PHYS_BINDING_SMBUS		= 0x01,
345	MCTP_PHYS_BINDING_PCIE_VDM	= 0x02,
346	MCTP_PHYS_BINDING_USB		= 0x03,
347	MCTP_PHYS_BINDING_KCS		= 0x04,
348	MCTP_PHYS_BINDING_SERIAL	= 0x05,
349	MCTP_PHYS_BINDING_I3C		= 0x06,
350	MCTP_PHYS_BINDING_MMBI		= 0x07,
351	MCTP_PHYS_BINDING_PCC		= 0x08,
352	MCTP_PHYS_BINDING_UCIE		= 0x09,
353	MCTP_PHYS_BINDING_VENDOR	= 0xFF,
354};
355
356#endif /* __NET_MCTP_H */