llc_station.c revision 025e36332573177ecd7c12730e18a4390f994f05 
1/*
2 * llc_station.c - station component of LLC
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#include <linux/init.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17#include <net/llc.h>
18#include <net/llc_sap.h>
19#include <net/llc_conn.h>
20#include <net/llc_c_ac.h>
21#include <net/llc_s_ac.h>
22#include <net/llc_c_ev.h>
23#include <net/llc_c_st.h>
24#include <net/llc_s_ev.h>
25#include <net/llc_s_st.h>
26#include <net/llc_pdu.h>
27
28/**
29 * struct llc_station - LLC station component
30 *
31 * SAP and connection resource manager, one per adapter.
32 *
33 * @mac_sa: MAC source address
34 * @sap_list: list of related SAPs
35 * @ev_q: events entering state mach.
36 * @mac_pdu_q: PDUs ready to send to MAC
37 */
38struct llc_station {
39	struct {
40		struct sk_buff_head list;
41		spinlock_t	    lock;
42	} ev_q;
43	struct sk_buff_head	    mac_pdu_q;
44};
45
46typedef int (*llc_station_ev_t)(struct sk_buff *skb);
47
48typedef int (*llc_station_action_t)(struct sk_buff *skb);
49
50/* Station component state table structure */
51struct llc_station_state_trans {
52	llc_station_ev_t ev;
53	llc_station_action_t *ev_actions;
54};
55
56static struct llc_station llc_main_station;
57
58static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
59{
60	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
61
62	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
63	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
64	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
65	       !pdu->dsap ? 0 : 1;			/* NULL DSAP value */
66}
67
68static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
69{
70	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
71
72	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
73	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
74	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
75	       !pdu->dsap ? 0 : 1;			/* NULL DSAP */
76}
77
78/**
79 *	llc_station_send_pdu - queues PDU to send
80 *	@skb: Address of the PDU
81 *
82 *	Queues a PDU to send to the MAC layer.
83 */
84static void llc_station_send_pdu(struct sk_buff *skb)
85{
86	skb_queue_tail(&llc_main_station.mac_pdu_q, skb);
87	while ((skb = skb_dequeue(&llc_main_station.mac_pdu_q)) != NULL)
88		if (dev_queue_xmit(skb))
89			break;
90}
91
92static int llc_station_ac_send_xid_r(struct sk_buff *skb)
93{
94	u8 mac_da[ETH_ALEN], dsap;
95	int rc = 1;
96	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
97					       sizeof(struct llc_xid_info));
98
99	if (!nskb)
100		goto out;
101	rc = 0;
102	llc_pdu_decode_sa(skb, mac_da);
103	llc_pdu_decode_ssap(skb, &dsap);
104	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
105	llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
106	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
107	if (unlikely(rc))
108		goto free;
109	llc_station_send_pdu(nskb);
110out:
111	return rc;
112free:
113	kfree_skb(nskb);
114	goto out;
115}
116
117static int llc_station_ac_send_test_r(struct sk_buff *skb)
118{
119	u8 mac_da[ETH_ALEN], dsap;
120	int rc = 1;
121	u32 data_size;
122	struct sk_buff *nskb;
123
124	/* The test request command is type U (llc_len = 3) */
125	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
126	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);
127
128	if (!nskb)
129		goto out;
130	rc = 0;
131	llc_pdu_decode_sa(skb, mac_da);
132	llc_pdu_decode_ssap(skb, &dsap);
133	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
134	llc_pdu_init_as_test_rsp(nskb, skb);
135	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
136	if (unlikely(rc))
137		goto free;
138	llc_station_send_pdu(nskb);
139out:
140	return rc;
141free:
142	kfree_skb(nskb);
143	goto out;
144}
145
146/* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
147static llc_station_action_t llc_stat_up_state_actions_2[] = {
148	[0] = llc_station_ac_send_xid_r,
149	[1] = NULL,
150};
151
152static struct llc_station_state_trans llc_stat_up_state_trans_2 = {
153	.ev	    = llc_stat_ev_rx_null_dsap_xid_c,
154	.ev_actions = llc_stat_up_state_actions_2,
155};
156
157/* state transition for LLC_STATION_EV_RX_NULL_DSAP_TEST_C event */
158static llc_station_action_t llc_stat_up_state_actions_3[] = {
159	[0] = llc_station_ac_send_test_r,
160	[1] = NULL,
161};
162
163static struct llc_station_state_trans llc_stat_up_state_trans_3 = {
164	.ev	    = llc_stat_ev_rx_null_dsap_test_c,
165	.ev_actions = llc_stat_up_state_actions_3,
166};
167
168/* array of pointers; one to each transition */
169static struct llc_station_state_trans *llc_stat_up_state_trans [] = {
170	&llc_stat_up_state_trans_2,
171	&llc_stat_up_state_trans_3,
172	NULL,
173};
174
175/**
176 *	llc_exec_station_trans_actions - executes actions for transition
177 *	@trans: Address of the transition
178 *	@skb: Address of the event that caused the transition
179 *
180 *	Executes actions of a transition of the station state machine. Returns
181 *	0 if all actions complete successfully, nonzero otherwise.
182 */
183static u16 llc_exec_station_trans_actions(struct llc_station_state_trans *trans,
184					  struct sk_buff *skb)
185{
186	u16 rc = 0;
187	llc_station_action_t *next_action = trans->ev_actions;
188
189	for (; next_action && *next_action; next_action++)
190		if ((*next_action)(skb))
191			rc = 1;
192	return rc;
193}
194
195/**
196 *	llc_find_station_trans - finds transition for this event
197 *	@skb: Address of the event
198 *
199 *	Search thru events of the current state of the station until list
200 *	exhausted or it's obvious that the event is not valid for the current
201 *	state. Returns the address of the transition if cound, %NULL otherwise.
202 */
203static struct llc_station_state_trans *
204				llc_find_station_trans(struct sk_buff *skb)
205{
206	int i = 0;
207	struct llc_station_state_trans *rc = NULL;
208	struct llc_station_state_trans **next_trans;
209
210	for (next_trans = llc_stat_up_state_trans; next_trans[i]; i++)
211		if (!next_trans[i]->ev(skb)) {
212			rc = next_trans[i];
213			break;
214		}
215	return rc;
216}
217
218/**
219 *	llc_station_free_ev - frees an event
220 *	@skb: Address of the event
221 *
222 *	Frees an event.
223 */
224static void llc_station_free_ev(struct sk_buff *skb)
225{
226	kfree_skb(skb);
227}
228
229/**
230 *	llc_station_next_state - processes event and goes to the next state
231 *	@skb: Address of the event
232 *
233 *	Processes an event, executes any transitions related to that event and
234 *	updates the state of the station.
235 */
236static u16 llc_station_next_state(struct sk_buff *skb)
237{
238	u16 rc = 1;
239	struct llc_station_state_trans *trans;
240
241	trans = llc_find_station_trans(skb);
242	if (trans)
243		/* got the state to which we next transition; perform the
244		 * actions associated with this transition before actually
245		 * transitioning to the next state
246		 */
247		rc = llc_exec_station_trans_actions(trans, skb);
248	else
249		/* event not recognized in current state; re-queue it for
250		 * processing again at a later time; return failure
251		 */
252		rc = 0;
253	llc_station_free_ev(skb);
254	return rc;
255}
256
257/**
258 *	llc_station_service_events - service events in the queue
259 *
260 *	Get an event from the station event queue (if any); attempt to service
261 *	the event; if event serviced, get the next event (if any) on the event
262 *	queue; if event not service, re-queue the event on the event queue and
263 *	attempt to service the next event; when serviced all events in queue,
264 *	finished; if don't transition to different state, just service all
265 *	events once; if transition to new state, service all events again.
266 *	Caller must hold llc_main_station.ev_q.lock.
267 */
268static void llc_station_service_events(void)
269{
270	struct sk_buff *skb;
271
272	while ((skb = skb_dequeue(&llc_main_station.ev_q.list)) != NULL)
273		llc_station_next_state(skb);
274}
275
276/**
277 *	llc_station_state_process - queue event and try to process queue.
278 *	@skb: Address of the event
279 *
280 *	Queues an event (on the station event queue) for handling by the
281 *	station state machine and attempts to process any queued-up events.
282 */
283static void llc_station_state_process(struct sk_buff *skb)
284{
285	spin_lock_bh(&llc_main_station.ev_q.lock);
286	skb_queue_tail(&llc_main_station.ev_q.list, skb);
287	llc_station_service_events();
288	spin_unlock_bh(&llc_main_station.ev_q.lock);
289}
290
291/**
292 *	llc_station_rcv - send received pdu to the station state machine
293 *	@skb: received frame.
294 *
295 *	Sends data unit to station state machine.
296 */
297static void llc_station_rcv(struct sk_buff *skb)
298{
299	llc_station_state_process(skb);
300}
301
302void __init llc_station_init(void)
303{
304	skb_queue_head_init(&llc_main_station.mac_pdu_q);
305	skb_queue_head_init(&llc_main_station.ev_q.list);
306	spin_lock_init(&llc_main_station.ev_q.lock);
307	llc_set_station_handler(llc_station_rcv);
308}
309
310void llc_station_exit(void)
311{
312	llc_set_station_handler(NULL);
313}
314