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 */
19 struct 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_HEADER_MAXLEN	4
40 
41 #define MCTP_INITIAL_DEFAULT_NET	1
42 
mctp_address_ok(mctp_eid_t eid)43 static inline bool mctp_address_ok(mctp_eid_t eid)
44 {
45 	return eid >= 8 && eid < 255;
46 }
47 
mctp_hdr(struct sk_buff * skb)48 static inline struct mctp_hdr *mctp_hdr(struct sk_buff *skb)
49 {
50 	return (struct mctp_hdr *)skb_network_header(skb);
51 }
52 
53 /* socket implementation */
54 struct mctp_sock {
55 	struct sock	sk;
56 
57 	/* bind() params */
58 	unsigned int	bind_net;
59 	mctp_eid_t	bind_addr;
60 	__u8		bind_type;
61 
62 	/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
63 	bool		addr_ext;
64 
65 	/* list of mctp_sk_key, for incoming tag lookup. updates protected
66 	 * by sk->net->keys_lock
67 	 */
68 	struct hlist_head keys;
69 
70 	/* mechanism for expiring allocated keys; will release an allocated
71 	 * tag, and any netdev state for a request/response pairing
72 	 */
73 	struct timer_list key_expiry;
74 };
75 
76 /* Key for matching incoming packets to sockets or reassembly contexts.
77  * Packets are matched on (src,dest,tag).
78  *
79  * Lifetime / locking requirements:
80  *
81  *  - individual key data (ie, the struct itself) is protected by key->lock;
82  *    changes must be made with that lock held.
83  *
84  *  - the lookup fields: peer_addr, local_addr and tag are set before the
85  *    key is added to lookup lists, and never updated.
86  *
87  *  - A ref to the key must be held (throuh key->refs) if a pointer to the
88  *    key is to be accessed after key->lock is released.
89  *
90  *  - a mctp_sk_key contains a reference to a struct sock; this is valid
91  *    for the life of the key. On sock destruction (through unhash), the key is
92  *    removed from lists (see below), and marked invalid.
93  *
94  * - these mctp_sk_keys appear on two lists:
95  *     1) the struct mctp_sock->keys list
96  *     2) the struct netns_mctp->keys list
97  *
98  *   presences on these lists requires a (single) refcount to be held; both
99  *   lists are updated as a single operation.
100  *
101  *   Updates and lookups in either list are performed under the
102  *   netns_mctp->keys lock. Lookup functions will need to lock the key and
103  *   take a reference before unlocking the keys_lock. Consequently, the list's
104  *   keys_lock *cannot* be acquired with the individual key->lock held.
105  *
106  * - a key may have a sk_buff attached as part of an in-progress message
107  *   reassembly (->reasm_head). The reasm data is protected by the individual
108  *   key->lock.
109  *
110  * - there are two destruction paths for a mctp_sk_key:
111  *
112  *    - through socket unhash (see mctp_sk_unhash). This performs the list
113  *      removal under keys_lock.
114  *
115  *    - where a key is established to receive a reply message: after receiving
116  *      the (complete) reply, or during reassembly errors. Here, we clean up
117  *      the reassembly context (marking reasm_dead, to prevent another from
118  *      starting), and remove the socket from the netns & socket lists.
119  *
120  *    - through an expiry timeout, on a per-socket timer
121  */
122 struct mctp_sk_key {
123 	mctp_eid_t	peer_addr;
124 	mctp_eid_t	local_addr;
125 	__u8		tag; /* incoming tag match; invert TO for local */
126 
127 	/* we hold a ref to sk when set */
128 	struct sock	*sk;
129 
130 	/* routing lookup list */
131 	struct hlist_node hlist;
132 
133 	/* per-socket list */
134 	struct hlist_node sklist;
135 
136 	/* lock protects against concurrent updates to the reassembly and
137 	 * expiry data below.
138 	 */
139 	spinlock_t	lock;
140 
141 	/* Keys are referenced during the output path, which may sleep */
142 	refcount_t	refs;
143 
144 	/* incoming fragment reassembly context */
145 	struct sk_buff	*reasm_head;
146 	struct sk_buff	**reasm_tailp;
147 	bool		reasm_dead;
148 	u8		last_seq;
149 
150 	/* key validity */
151 	bool		valid;
152 
153 	/* expiry timeout; valid (above) cleared on expiry */
154 	unsigned long	expiry;
155 
156 	/* free to use for device flow state tracking. Initialised to
157 	 * zero on initial key creation
158 	 */
159 	unsigned long	dev_flow_state;
160 	struct mctp_dev	*dev;
161 };
162 
163 struct mctp_skb_cb {
164 	unsigned int	magic;
165 	unsigned int	net;
166 	int		ifindex; /* extended/direct addressing if set */
167 	mctp_eid_t	src;
168 	unsigned char	halen;
169 	unsigned char	haddr[MAX_ADDR_LEN];
170 };
171 
172 /* skb control-block accessors with a little extra debugging for initial
173  * development.
174  *
175  * TODO: remove checks & mctp_skb_cb->magic; replace callers of __mctp_cb
176  * with mctp_cb().
177  *
178  * __mctp_cb() is only for the initial ingress code; we should see ->magic set
179  * at all times after this.
180  */
__mctp_cb(struct sk_buff * skb)181 static inline struct mctp_skb_cb *__mctp_cb(struct sk_buff *skb)
182 {
183 	struct mctp_skb_cb *cb = (void *)skb->cb;
184 
185 	cb->magic = 0x4d435450;
186 	return cb;
187 }
188 
mctp_cb(struct sk_buff * skb)189 static inline struct mctp_skb_cb *mctp_cb(struct sk_buff *skb)
190 {
191 	struct mctp_skb_cb *cb = (void *)skb->cb;
192 
193 	BUILD_BUG_ON(sizeof(struct mctp_skb_cb) > sizeof(skb->cb));
194 	WARN_ON(cb->magic != 0x4d435450);
195 	return (void *)(skb->cb);
196 }
197 
198 /* If CONFIG_MCTP_FLOWS, we may add one of these as a SKB extension,
199  * indicating the flow to the device driver.
200  */
201 struct mctp_flow {
202 	struct mctp_sk_key *key;
203 };
204 
205 /* Route definition.
206  *
207  * These are held in the pernet->mctp.routes list, with RCU protection for
208  * removed routes. We hold a reference to the netdev; routes need to be
209  * dropped on NETDEV_UNREGISTER events.
210  *
211  * Updates to the route table are performed under rtnl; all reads under RCU,
212  * so routes cannot be referenced over a RCU grace period. Specifically: A
213  * caller cannot block between mctp_route_lookup and mctp_route_release()
214  */
215 struct mctp_route {
216 	mctp_eid_t		min, max;
217 
218 	struct mctp_dev		*dev;
219 	unsigned int		mtu;
220 	unsigned char		type;
221 	int			(*output)(struct mctp_route *route,
222 					  struct sk_buff *skb);
223 
224 	struct list_head	list;
225 	refcount_t		refs;
226 	struct rcu_head		rcu;
227 };
228 
229 /* route interfaces */
230 struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
231 				     mctp_eid_t daddr);
232 
233 int mctp_local_output(struct sock *sk, struct mctp_route *rt,
234 		      struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag);
235 
236 void mctp_key_unref(struct mctp_sk_key *key);
237 
238 /* routing <--> device interface */
239 unsigned int mctp_default_net(struct net *net);
240 int mctp_default_net_set(struct net *net, unsigned int index);
241 int mctp_route_add_local(struct mctp_dev *mdev, mctp_eid_t addr);
242 int mctp_route_remove_local(struct mctp_dev *mdev, mctp_eid_t addr);
243 void mctp_route_remove_dev(struct mctp_dev *mdev);
244 
245 /* neighbour definitions */
246 enum mctp_neigh_source {
247 	MCTP_NEIGH_STATIC,
248 	MCTP_NEIGH_DISCOVER,
249 };
250 
251 struct mctp_neigh {
252 	struct mctp_dev		*dev;
253 	mctp_eid_t		eid;
254 	enum mctp_neigh_source	source;
255 
256 	unsigned char		ha[MAX_ADDR_LEN];
257 
258 	struct list_head	list;
259 	struct rcu_head		rcu;
260 };
261 
262 int mctp_neigh_init(void);
263 void mctp_neigh_exit(void);
264 
265 // ret_hwaddr may be NULL, otherwise must have space for MAX_ADDR_LEN
266 int mctp_neigh_lookup(struct mctp_dev *dev, mctp_eid_t eid,
267 		      void *ret_hwaddr);
268 void mctp_neigh_remove_dev(struct mctp_dev *mdev);
269 
270 int mctp_routes_init(void);
271 void mctp_routes_exit(void);
272 
273 void mctp_device_init(void);
274 void mctp_device_exit(void);
275 
276 #endif /* __NET_MCTP_H */
277