net/llc/llc_station.c

   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  */
  38 struct 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
  46 typedef int (*llc_station_ev_t)(struct sk_buff *skb);
  47
  48 typedef int (*llc_station_action_t)(struct sk_buff *skb);
  49
  50 /* Station component state table structure */
  51 struct llc_station_state_trans {
  52         llc_station_ev_t ev;
  53         llc_station_action_t *ev_actions;
  54 };
  55
  56 static struct llc_station llc_main_station;
  57
  58 static 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
  68 static 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  */
  84 static 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
  92 static 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);
 110 out:
 111         return rc;
 112 free:
 113         kfree_skb(nskb);
 114         goto out;
 115 }
 116
 117 static 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);
 139 out:
 140         return rc;
 141 free:
 142         kfree_skb(nskb);
 143         goto out;
 144 }
 145
 146 /* state transition for LLC_STATION_EV_RX_NULL_DSAP_XID_C event */
 147 static llc_station_action_t llc_stat_up_state_actions_2[] = {
 148         [0] = llc_station_ac_send_xid_r,
 149         [1] = NULL,
 150 };
 151
 152 static 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 */
 158 static llc_station_action_t llc_stat_up_state_actions_3[] = {
 159         [0] = llc_station_ac_send_test_r,
 160         [1] = NULL,
 161 };
 162
 163 static 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 */
 169 static 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  */
 183 static 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  */
 203 static 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  */
 224 static 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  */
 236 static 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  */
 268 static 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  */
 283 static 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  */
 297 static void llc_station_rcv(struct sk_buff *skb)
 298 {
 299         llc_station_state_process(skb);
 300 }
 301
 302 void __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
 310 void llc_station_exit(void)
 311 {
 312         llc_set_station_handler(NULL);
 313 }