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_addr;
73	__u8		bind_type;
74
75	/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
76	bool		addr_ext;
77
78	/* list of mctp_sk_key, for incoming tag lookup. updates protected
79	 * by sk->net->keys_lock
80	 */
81	struct hlist_head keys;
82
83	/* mechanism for expiring allocated keys; will release an allocated
84	 * tag, and any netdev state for a request/response pairing
85	 */
86	struct timer_list key_expiry;
87};
88
89/* Key for matching incoming packets to sockets or reassembly contexts.
90 * Packets are matched on (peer EID, local EID, tag).
91 *
92 * Lifetime / locking requirements:
93 *
94 *  - individual key data (ie, the struct itself) is protected by key->lock;
95 *    changes must be made with that lock held.
96 *
97 *  - the lookup fields: peer_addr, local_addr and tag are set before the
98 *    key is added to lookup lists, and never updated.
99 *
100 *  - A ref to the key must be held (throuh key->refs) if a pointer to the
101 *    key is to be accessed after key->lock is released.
102 *
103 *  - a mctp_sk_key contains a reference to a struct sock; this is valid
104 *    for the life of the key. On sock destruction (through unhash), the key is
105 *    removed from lists (see below), and marked invalid.
106 *
107 * - these mctp_sk_keys appear on two lists:
108 *     1) the struct mctp_sock->keys list
109 *     2) the struct netns_mctp->keys list
110 *
111 *   presences on these lists requires a (single) refcount to be held; both
112 *   lists are updated as a single operation.
113 *
114 *   Updates and lookups in either list are performed under the
115 *   netns_mctp->keys lock. Lookup functions will need to lock the key and
116 *   take a reference before unlocking the keys_lock. Consequently, the list's
117 *   keys_lock *cannot* be acquired with the individual key->lock held.
118 *
119 * - a key may have a sk_buff attached as part of an in-progress message
120 *   reassembly (->reasm_head). The reasm data is protected by the individual
121 *   key->lock.
122 *
123 * - there are two destruction paths for a mctp_sk_key:
124 *
125 *    - through socket unhash (see mctp_sk_unhash). This performs the list
126 *      removal under keys_lock.
127 *
128 *    - where a key is established to receive a reply message: after receiving
129 *      the (complete) reply, or during reassembly errors. Here, we clean up
130 *      the reassembly context (marking reasm_dead, to prevent another from
131 *      starting), and remove the socket from the netns & socket lists.
132 *
133 *    - through an expiry timeout, on a per-socket timer
134 */
135struct mctp_sk_key {
136	unsigned int	net;
137	mctp_eid_t	peer_addr;
138	mctp_eid_t	local_addr; /* MCTP_ADDR_ANY for local owned tags */
139	__u8		tag; /* incoming tag match; invert TO for local */
140
141	/* we hold a ref to sk when set */
142	struct sock	*sk;
143
144	/* routing lookup list */
145	struct hlist_node hlist;
146
147	/* per-socket list */
148	struct hlist_node sklist;
149
150	/* lock protects against concurrent updates to the reassembly and
151	 * expiry data below.
152	 */
153	spinlock_t	lock;
154
155	/* Keys are referenced during the output path, which may sleep */
156	refcount_t	refs;
157
158	/* incoming fragment reassembly context */
159	struct sk_buff	*reasm_head;
160	struct sk_buff	**reasm_tailp;
161	bool		reasm_dead;
162	u8		last_seq;
163
164	/* key validity */
165	bool		valid;
166
167	/* expiry timeout; valid (above) cleared on expiry */
168	unsigned long	expiry;
169
170	/* free to use for device flow state tracking. Initialised to
171	 * zero on initial key creation
172	 */
173	unsigned long	dev_flow_state;
174	struct mctp_dev	*dev;
175
176	/* a tag allocated with SIOCMCTPALLOCTAG ioctl will not expire
177	 * automatically on timeout or response, instead SIOCMCTPDROPTAG
178	 * is used.
179	 */
180	bool		manual_alloc;
181};
182
183struct mctp_skb_cb {
184	unsigned int	magic;
185	unsigned int	net;
186	int		ifindex; /* extended/direct addressing if set */
187	mctp_eid_t	src;
188	unsigned char	halen;
189	unsigned char	haddr[MAX_ADDR_LEN];
190};
191
192/* skb control-block accessors with a little extra debugging for initial
193 * development.
194 *
195 * TODO: remove checks & mctp_skb_cb->magic; replace callers of __mctp_cb
196 * with mctp_cb().
197 *
198 * __mctp_cb() is only for the initial ingress code; we should see ->magic set
199 * at all times after this.
200 */
201static inline struct mctp_skb_cb *__mctp_cb(struct sk_buff *skb)
202{
203	struct mctp_skb_cb *cb = (void *)skb->cb;
204
205	cb->magic = 0x4d435450;
206	return cb;
207}
208
209static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
210{
211	struct mctp_skb_cb *cb = (void *)skb->cb;
212
213	BUILD_BUG_ON(sizeof(struct mctp_skb_cb) > sizeof(skb->cb));
214	WARN_ON(cb->magic != 0x4d435450);
215	return (void *)(skb->cb);
216}
217
218/* If CONFIG_MCTP_FLOWS, we may add one of these as a SKB extension,
219 * indicating the flow to the device driver.
220 */
221struct mctp_flow {
222	struct mctp_sk_key *key;
223};
224
225/* Route definition.
226 *
227 * These are held in the pernet->mctp.routes list, with RCU protection for
228 * removed routes. We hold a reference to the netdev; routes need to be
229 * dropped on NETDEV_UNREGISTER events.
230 *
231 * Updates to the route table are performed under rtnl; all reads under RCU,
232 * so routes cannot be referenced over a RCU grace period. Specifically: A
233 * caller cannot block between mctp_route_lookup and mctp_route_release()
234 */
235struct mctp_route {
236	mctp_eid_t		min, max;
237
238	unsigned char		type;
239	unsigned int		mtu;
240	struct mctp_dev		*dev;
241	int			(*output)(struct mctp_route *route,
242					  struct sk_buff *skb);
243
244	struct list_head	list;
245	refcount_t		refs;
246	struct rcu_head		rcu;
247};
248
249/* route interfaces */
250struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
251				     mctp_eid_t daddr);
252
253/* always takes ownership of skb */
254int mctp_local_output(struct sock *sk, struct mctp_route *rt,
255		      struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag);
256
257void mctp_key_unref(struct mctp_sk_key *key);
258struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
259					 unsigned int netid,
260					 mctp_eid_t local, mctp_eid_t peer,
261					 bool manual, u8 *tagp);
262
263/* routing <--> device interface */
264unsigned int mctp_default_net(struct net *net);
265int mctp_default_net_set(struct net *net, unsigned int index);
266int mctp_route_add_local(struct mctp_dev *mdev, mctp_eid_t addr);
267int mctp_route_remove_local(struct mctp_dev *mdev, mctp_eid_t addr);
268void mctp_route_remove_dev(struct mctp_dev *mdev);
269
270/* neighbour definitions */
271enum mctp_neigh_source {
272	MCTP_NEIGH_STATIC,
273	MCTP_NEIGH_DISCOVER,
274};
275
276struct mctp_neigh {
277	struct mctp_dev		*dev;
278	mctp_eid_t		eid;
279	enum mctp_neigh_source	source;
280
281	unsigned char		ha[MAX_ADDR_LEN];
282
283	struct list_head	list;
284	struct rcu_head		rcu;
285};
286
287int mctp_neigh_init(void);
288void mctp_neigh_exit(void);
289
290// ret_hwaddr may be NULL, otherwise must have space for MAX_ADDR_LEN
291int mctp_neigh_lookup(struct mctp_dev *dev, mctp_eid_t eid,
292		      void *ret_hwaddr);
293void mctp_neigh_remove_dev(struct mctp_dev *mdev);
294
295int mctp_routes_init(void);
296void mctp_routes_exit(void);
297
298void mctp_device_init(void);
299void mctp_device_exit(void);
300
301#endif /* __NET_MCTP_H */
302