llc_sap.c revision 0f7b67dd9e1192976f5e5a78934c7a339ff7c45f 
1/*
2 * llc_sap.c - driver routines for SAP component.
3 *
4 * Copyright (c) 1997 by Procom Technology, Inc.
5 * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
6 *
7 * This program can be redistributed or modified under the terms of the
8 * GNU General Public License as published by the Free Software Foundation.
9 * This program is distributed without any warranty or implied warranty
10 * of merchantability or fitness for a particular purpose.
11 *
12 * See the GNU General Public License for more details.
13 */
14
15#include <net/llc.h>
16#include <net/llc_if.h>
17#include <net/llc_conn.h>
18#include <net/llc_pdu.h>
19#include <net/llc_sap.h>
20#include <net/llc_s_ac.h>
21#include <net/llc_s_ev.h>
22#include <net/llc_s_st.h>
23#include <net/sock.h>
24#include <net/tcp_states.h>
25#include <linux/llc.h>
26
27static int llc_mac_header_len(unsigned short devtype)
28{
29	switch (devtype) {
30	case ARPHRD_ETHER:
31	case ARPHRD_LOOPBACK:
32		return sizeof(struct ethhdr);
33#ifdef CONFIG_TR
34	case ARPHRD_IEEE802_TR:
35		return sizeof(struct trh_hdr);
36#endif
37	}
38	return 0;
39}
40
41/**
42 *	llc_alloc_frame - allocates sk_buff for frame
43 *	@dev: network device this skb will be sent over
44 *	@type: pdu type to allocate
45 *	@data_size: data size to allocate
46 *
47 *	Allocates an sk_buff for frame and initializes sk_buff fields.
48 *	Returns allocated skb or %NULL when out of memory.
49 */
50struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
51				u8 type, u32 data_size)
52{
53	int hlen = type == LLC_PDU_TYPE_U ? 3 : 4;
54	struct sk_buff *skb;
55
56	hlen += llc_mac_header_len(dev->type);
57	skb = alloc_skb(hlen + data_size, GFP_ATOMIC);
58
59	if (skb) {
60		skb_reset_mac_header(skb);
61		skb_reserve(skb, hlen);
62		skb_reset_network_header(skb);
63		skb_reset_transport_header(skb);
64		skb->protocol = htons(ETH_P_802_2);
65		skb->dev      = dev;
66		if (sk != NULL)
67			skb_set_owner_w(skb, sk);
68	}
69	return skb;
70}
71
72void llc_save_primitive(struct sock *sk, struct sk_buff* skb, u8 prim)
73{
74	struct sockaddr_llc *addr;
75
76       /* save primitive for use by the user. */
77	addr		  = llc_ui_skb_cb(skb);
78
79	memset(addr, 0, sizeof(*addr));
80	addr->sllc_family = sk->sk_family;
81	addr->sllc_arphrd = skb->dev->type;
82	addr->sllc_test   = prim == LLC_TEST_PRIM;
83	addr->sllc_xid    = prim == LLC_XID_PRIM;
84	addr->sllc_ua     = prim == LLC_DATAUNIT_PRIM;
85	llc_pdu_decode_sa(skb, addr->sllc_mac);
86	llc_pdu_decode_ssap(skb, &addr->sllc_sap);
87}
88
89/**
90 *	llc_sap_rtn_pdu - Informs upper layer on rx of an UI, XID or TEST pdu.
91 *	@sap: pointer to SAP
92 *	@skb: received pdu
93 */
94void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb)
95{
96	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
97	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
98
99	switch (LLC_U_PDU_RSP(pdu)) {
100	case LLC_1_PDU_CMD_TEST:
101		ev->prim = LLC_TEST_PRIM;	break;
102	case LLC_1_PDU_CMD_XID:
103		ev->prim = LLC_XID_PRIM;	break;
104	case LLC_1_PDU_CMD_UI:
105		ev->prim = LLC_DATAUNIT_PRIM;	break;
106	}
107	ev->ind_cfm_flag = LLC_IND;
108}
109
110/**
111 *	llc_find_sap_trans - finds transition for event
112 *	@sap: pointer to SAP
113 *	@skb: happened event
114 *
115 *	This function finds transition that matches with happened event.
116 *	Returns the pointer to found transition on success or %NULL for
117 *	failure.
118 */
119static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
120						      struct sk_buff* skb)
121{
122	int i = 0;
123	struct llc_sap_state_trans *rc = NULL;
124	struct llc_sap_state_trans **next_trans;
125	struct llc_sap_state *curr_state = &llc_sap_state_table[sap->state - 1];
126	/*
127	 * Search thru events for this state until list exhausted or until
128	 * its obvious the event is not valid for the current state
129	 */
130	for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
131		if (!next_trans[i]->ev(sap, skb)) {
132			rc = next_trans[i]; /* got event match; return it */
133			break;
134		}
135	return rc;
136}
137
138/**
139 *	llc_exec_sap_trans_actions - execute actions related to event
140 *	@sap: pointer to SAP
141 *	@trans: pointer to transition that it's actions must be performed
142 *	@skb: happened event.
143 *
144 *	This function executes actions that is related to happened event.
145 *	Returns 0 for success and 1 for failure of at least one action.
146 */
147static int llc_exec_sap_trans_actions(struct llc_sap *sap,
148				      struct llc_sap_state_trans *trans,
149				      struct sk_buff *skb)
150{
151	int rc = 0;
152	llc_sap_action_t *next_action = trans->ev_actions;
153
154	for (; next_action && *next_action; next_action++)
155		if ((*next_action)(sap, skb))
156			rc = 1;
157	return rc;
158}
159
160/**
161 *	llc_sap_next_state - finds transition, execs actions & change SAP state
162 *	@sap: pointer to SAP
163 *	@skb: happened event
164 *
165 *	This function finds transition that matches with happened event, then
166 *	executes related actions and finally changes state of SAP. It returns
167 *	0 on success and 1 for failure.
168 */
169static int llc_sap_next_state(struct llc_sap *sap, struct sk_buff *skb)
170{
171	int rc = 1;
172	struct llc_sap_state_trans *trans;
173
174	if (sap->state > LLC_NR_SAP_STATES)
175		goto out;
176	trans = llc_find_sap_trans(sap, skb);
177	if (!trans)
178		goto out;
179	/*
180	 * Got the state to which we next transition; perform the actions
181	 * associated with this transition before actually transitioning to the
182	 * next state
183	 */
184	rc = llc_exec_sap_trans_actions(sap, trans, skb);
185	if (rc)
186		goto out;
187	/*
188	 * Transition SAP to next state if all actions execute successfully
189	 */
190	sap->state = trans->next_state;
191out:
192	return rc;
193}
194
195/**
196 *	llc_sap_state_process - sends event to SAP state machine
197 *	@sap: sap to use
198 *	@skb: pointer to occurred event
199 *
200 *	After executing actions of the event, upper layer will be indicated
201 *	if needed(on receiving an UI frame). sk can be null for the
202 *	datalink_proto case.
203 */
204static void llc_sap_state_process(struct llc_sap *sap, struct sk_buff *skb)
205{
206	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
207
208	/*
209	 * We have to hold the skb, because llc_sap_next_state
210	 * will kfree it in the sending path and we need to
211	 * look at the skb->cb, where we encode llc_sap_state_ev.
212	 */
213	skb_get(skb);
214	ev->ind_cfm_flag = 0;
215	llc_sap_next_state(sap, skb);
216	if (ev->ind_cfm_flag == LLC_IND) {
217		if (skb->sk->sk_state == TCP_LISTEN)
218			kfree_skb(skb);
219		else {
220			llc_save_primitive(skb->sk, skb, ev->prim);
221
222			/* queue skb to the user. */
223			if (sock_queue_rcv_skb(skb->sk, skb))
224				kfree_skb(skb);
225		}
226	}
227	kfree_skb(skb);
228}
229
230/**
231 *	llc_build_and_send_test_pkt - TEST interface for upper layers.
232 *	@sap: sap to use
233 *	@skb: packet to send
234 *	@dmac: destination mac address
235 *	@dsap: destination sap
236 *
237 *	This function is called when upper layer wants to send a TEST pdu.
238 *	Returns 0 for success, 1 otherwise.
239 */
240void llc_build_and_send_test_pkt(struct llc_sap *sap,
241				 struct sk_buff *skb, u8 *dmac, u8 dsap)
242{
243	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
244
245	ev->saddr.lsap = sap->laddr.lsap;
246	ev->daddr.lsap = dsap;
247	memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
248	memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
249
250	ev->type      = LLC_SAP_EV_TYPE_PRIM;
251	ev->prim      = LLC_TEST_PRIM;
252	ev->prim_type = LLC_PRIM_TYPE_REQ;
253	llc_sap_state_process(sap, skb);
254}
255
256/**
257 *	llc_build_and_send_xid_pkt - XID interface for upper layers
258 *	@sap: sap to use
259 *	@skb: packet to send
260 *	@dmac: destination mac address
261 *	@dsap: destination sap
262 *
263 *	This function is called when upper layer wants to send a XID pdu.
264 *	Returns 0 for success, 1 otherwise.
265 */
266void llc_build_and_send_xid_pkt(struct llc_sap *sap, struct sk_buff *skb,
267				u8 *dmac, u8 dsap)
268{
269	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
270
271	ev->saddr.lsap = sap->laddr.lsap;
272	ev->daddr.lsap = dsap;
273	memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
274	memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
275
276	ev->type      = LLC_SAP_EV_TYPE_PRIM;
277	ev->prim      = LLC_XID_PRIM;
278	ev->prim_type = LLC_PRIM_TYPE_REQ;
279	llc_sap_state_process(sap, skb);
280}
281
282/**
283 *	llc_sap_rcv - sends received pdus to the sap state machine
284 *	@sap: current sap component structure.
285 *	@skb: received frame.
286 *
287 *	Sends received pdus to the sap state machine.
288 */
289static void llc_sap_rcv(struct llc_sap *sap, struct sk_buff *skb,
290			struct sock *sk)
291{
292	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
293
294	ev->type   = LLC_SAP_EV_TYPE_PDU;
295	ev->reason = 0;
296	skb->sk = sk;
297	llc_sap_state_process(sap, skb);
298}
299
300static inline bool llc_dgram_match(const struct llc_sap *sap,
301				   const struct llc_addr *laddr,
302				   const struct sock *sk)
303{
304     struct llc_sock *llc = llc_sk(sk);
305
306     return sk->sk_type == SOCK_DGRAM &&
307	  llc->laddr.lsap == laddr->lsap &&
308	  llc_mac_match(llc->laddr.mac, laddr->mac);
309}
310
311/**
312 *	llc_lookup_dgram - Finds dgram socket for the local sap/mac
313 *	@sap: SAP
314 *	@laddr: address of local LLC (MAC + SAP)
315 *
316 *	Search socket list of the SAP and finds connection using the local
317 *	mac, and local sap. Returns pointer for socket found, %NULL otherwise.
318 */
319static struct sock *llc_lookup_dgram(struct llc_sap *sap,
320				     const struct llc_addr *laddr)
321{
322	struct sock *rc;
323	struct hlist_nulls_node *node;
324
325	rcu_read_lock_bh();
326again:
327	sk_nulls_for_each_rcu(rc, node, &sap->sk_list) {
328		if (llc_dgram_match(sap, laddr, rc)) {
329			/* Extra checks required by SLAB_DESTROY_BY_RCU */
330			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
331				goto again;
332			if (unlikely(llc_sk(rc)->sap != sap ||
333				     !llc_dgram_match(sap, laddr, rc))) {
334				sock_put(rc);
335				continue;
336			}
337			goto found;
338		}
339	}
340	rc = NULL;
341found:
342	rcu_read_unlock_bh();
343	return rc;
344}
345
346static inline bool llc_mcast_match(const struct llc_sap *sap,
347				   const struct llc_addr *laddr,
348				   const struct sk_buff *skb,
349				   const struct sock *sk)
350{
351     struct llc_sock *llc = llc_sk(sk);
352
353     return sk->sk_type == SOCK_DGRAM &&
354	  llc->laddr.lsap == laddr->lsap &&
355	  llc->dev == skb->dev;
356}
357
358static void llc_do_mcast(struct llc_sap *sap, struct sk_buff *skb,
359			 struct sock **stack, int count)
360{
361	struct sk_buff *skb1;
362	int i;
363
364	for (i = 0; i < count; i++) {
365		skb1 = skb_clone(skb, GFP_ATOMIC);
366		if (!skb1) {
367			sock_put(stack[i]);
368			continue;
369		}
370
371		llc_sap_rcv(sap, skb1, stack[i]);
372		sock_put(stack[i]);
373	}
374}
375
376/**
377 * 	llc_sap_mcast - Deliver multicast PDU's to all matching datagram sockets.
378 *	@sap: SAP
379 *	@laddr: address of local LLC (MAC + SAP)
380 *
381 *	Search socket list of the SAP and finds connections with same sap.
382 *	Deliver clone to each.
383 */
384static void llc_sap_mcast(struct llc_sap *sap,
385			  const struct llc_addr *laddr,
386			  struct sk_buff *skb)
387{
388	int i = 0, count = 256 / sizeof(struct sock *);
389	struct sock *sk, *stack[count];
390	struct hlist_nulls_node *node;
391
392	spin_lock_bh(&sap->sk_lock);
393	sk_nulls_for_each_rcu(sk, node, &sap->sk_list) {
394
395		if (!llc_mcast_match(sap, laddr, skb, sk))
396			continue;
397
398		sock_hold(sk);
399		if (i < count)
400			stack[i++] = sk;
401		else {
402			llc_do_mcast(sap, skb, stack, i);
403			i = 0;
404		}
405	}
406	spin_unlock_bh(&sap->sk_lock);
407
408	llc_do_mcast(sap, skb, stack, i);
409}
410
411
412void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
413{
414	struct llc_addr laddr;
415
416	llc_pdu_decode_da(skb, laddr.mac);
417	llc_pdu_decode_dsap(skb, &laddr.lsap);
418
419	if (llc_mac_multicast(laddr.mac)) {
420		llc_sap_mcast(sap, &laddr, skb);
421		kfree_skb(skb);
422	} else {
423		struct sock *sk = llc_lookup_dgram(sap, &laddr);
424		if (sk) {
425			llc_sap_rcv(sap, skb, sk);
426			sock_put(sk);
427		} else
428			kfree_skb(skb);
429	}
430}
431