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Linux/net/llc/llc_sap.c

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  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 #include <linux/slab.h>
 27 
 28 static int llc_mac_header_len(unsigned short devtype)
 29 {
 30         switch (devtype) {
 31         case ARPHRD_ETHER:
 32         case ARPHRD_LOOPBACK:
 33                 return sizeof(struct ethhdr);
 34         }
 35         return 0;
 36 }
 37 
 38 /**
 39  *      llc_alloc_frame - allocates sk_buff for frame
 40  *      @dev: network device this skb will be sent over
 41  *      @type: pdu type to allocate
 42  *      @data_size: data size to allocate
 43  *
 44  *      Allocates an sk_buff for frame and initializes sk_buff fields.
 45  *      Returns allocated skb or %NULL when out of memory.
 46  */
 47 struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
 48                                 u8 type, u32 data_size)
 49 {
 50         int hlen = type == LLC_PDU_TYPE_U ? 3 : 4;
 51         struct sk_buff *skb;
 52 
 53         hlen += llc_mac_header_len(dev->type);
 54         skb = alloc_skb(hlen + data_size, GFP_ATOMIC);
 55 
 56         if (skb) {
 57                 skb_reset_mac_header(skb);
 58                 skb_reserve(skb, hlen);
 59                 skb_reset_network_header(skb);
 60                 skb_reset_transport_header(skb);
 61                 skb->protocol = htons(ETH_P_802_2);
 62                 skb->dev      = dev;
 63                 if (sk != NULL)
 64                         skb_set_owner_w(skb, sk);
 65         }
 66         return skb;
 67 }
 68 
 69 void llc_save_primitive(struct sock *sk, struct sk_buff *skb, u8 prim)
 70 {
 71         struct sockaddr_llc *addr;
 72 
 73        /* save primitive for use by the user. */
 74         addr              = llc_ui_skb_cb(skb);
 75 
 76         memset(addr, 0, sizeof(*addr));
 77         addr->sllc_family = sk->sk_family;
 78         addr->sllc_arphrd = skb->dev->type;
 79         addr->sllc_test   = prim == LLC_TEST_PRIM;
 80         addr->sllc_xid    = prim == LLC_XID_PRIM;
 81         addr->sllc_ua     = prim == LLC_DATAUNIT_PRIM;
 82         llc_pdu_decode_sa(skb, addr->sllc_mac);
 83         llc_pdu_decode_ssap(skb, &addr->sllc_sap);
 84 }
 85 
 86 /**
 87  *      llc_sap_rtn_pdu - Informs upper layer on rx of an UI, XID or TEST pdu.
 88  *      @sap: pointer to SAP
 89  *      @skb: received pdu
 90  */
 91 void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb)
 92 {
 93         struct llc_sap_state_ev *ev = llc_sap_ev(skb);
 94         struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
 95 
 96         switch (LLC_U_PDU_RSP(pdu)) {
 97         case LLC_1_PDU_CMD_TEST:
 98                 ev->prim = LLC_TEST_PRIM;       break;
 99         case LLC_1_PDU_CMD_XID:
100                 ev->prim = LLC_XID_PRIM;        break;
101         case LLC_1_PDU_CMD_UI:
102                 ev->prim = LLC_DATAUNIT_PRIM;   break;
103         }
104         ev->ind_cfm_flag = LLC_IND;
105 }
106 
107 /**
108  *      llc_find_sap_trans - finds transition for event
109  *      @sap: pointer to SAP
110  *      @skb: happened event
111  *
112  *      This function finds transition that matches with happened event.
113  *      Returns the pointer to found transition on success or %NULL for
114  *      failure.
115  */
116 static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
117                                                       struct sk_buff *skb)
118 {
119         int i = 0;
120         struct llc_sap_state_trans *rc = NULL;
121         struct llc_sap_state_trans **next_trans;
122         struct llc_sap_state *curr_state = &llc_sap_state_table[sap->state - 1];
123         /*
124          * Search thru events for this state until list exhausted or until
125          * its obvious the event is not valid for the current state
126          */
127         for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
128                 if (!next_trans[i]->ev(sap, skb)) {
129                         rc = next_trans[i]; /* got event match; return it */
130                         break;
131                 }
132         return rc;
133 }
134 
135 /**
136  *      llc_exec_sap_trans_actions - execute actions related to event
137  *      @sap: pointer to SAP
138  *      @trans: pointer to transition that it's actions must be performed
139  *      @skb: happened event.
140  *
141  *      This function executes actions that is related to happened event.
142  *      Returns 0 for success and 1 for failure of at least one action.
143  */
144 static int llc_exec_sap_trans_actions(struct llc_sap *sap,
145                                       struct llc_sap_state_trans *trans,
146                                       struct sk_buff *skb)
147 {
148         int rc = 0;
149         const llc_sap_action_t *next_action = trans->ev_actions;
150 
151         for (; next_action && *next_action; next_action++)
152                 if ((*next_action)(sap, skb))
153                         rc = 1;
154         return rc;
155 }
156 
157 /**
158  *      llc_sap_next_state - finds transition, execs actions & change SAP state
159  *      @sap: pointer to SAP
160  *      @skb: happened event
161  *
162  *      This function finds transition that matches with happened event, then
163  *      executes related actions and finally changes state of SAP. It returns
164  *      0 on success and 1 for failure.
165  */
166 static int llc_sap_next_state(struct llc_sap *sap, struct sk_buff *skb)
167 {
168         int rc = 1;
169         struct llc_sap_state_trans *trans;
170 
171         if (sap->state > LLC_NR_SAP_STATES)
172                 goto out;
173         trans = llc_find_sap_trans(sap, skb);
174         if (!trans)
175                 goto out;
176         /*
177          * Got the state to which we next transition; perform the actions
178          * associated with this transition before actually transitioning to the
179          * next state
180          */
181         rc = llc_exec_sap_trans_actions(sap, trans, skb);
182         if (rc)
183                 goto out;
184         /*
185          * Transition SAP to next state if all actions execute successfully
186          */
187         sap->state = trans->next_state;
188 out:
189         return rc;
190 }
191 
192 /**
193  *      llc_sap_state_process - sends event to SAP state machine
194  *      @sap: sap to use
195  *      @skb: pointer to occurred event
196  *
197  *      After executing actions of the event, upper layer will be indicated
198  *      if needed(on receiving an UI frame). sk can be null for the
199  *      datalink_proto case.
200  */
201 static void llc_sap_state_process(struct llc_sap *sap, struct sk_buff *skb)
202 {
203         struct llc_sap_state_ev *ev = llc_sap_ev(skb);
204 
205         /*
206          * We have to hold the skb, because llc_sap_next_state
207          * will kfree it in the sending path and we need to
208          * look at the skb->cb, where we encode llc_sap_state_ev.
209          */
210         skb_get(skb);
211         ev->ind_cfm_flag = 0;
212         llc_sap_next_state(sap, skb);
213         if (ev->ind_cfm_flag == LLC_IND) {
214                 if (skb->sk->sk_state == TCP_LISTEN)
215                         kfree_skb(skb);
216                 else {
217                         llc_save_primitive(skb->sk, skb, ev->prim);
218 
219                         /* queue skb to the user. */
220                         if (sock_queue_rcv_skb(skb->sk, skb))
221                                 kfree_skb(skb);
222                 }
223         }
224         kfree_skb(skb);
225 }
226 
227 /**
228  *      llc_build_and_send_test_pkt - TEST interface for upper layers.
229  *      @sap: sap to use
230  *      @skb: packet to send
231  *      @dmac: destination mac address
232  *      @dsap: destination sap
233  *
234  *      This function is called when upper layer wants to send a TEST pdu.
235  *      Returns 0 for success, 1 otherwise.
236  */
237 void llc_build_and_send_test_pkt(struct llc_sap *sap,
238                                  struct sk_buff *skb, u8 *dmac, u8 dsap)
239 {
240         struct llc_sap_state_ev *ev = llc_sap_ev(skb);
241 
242         ev->saddr.lsap = sap->laddr.lsap;
243         ev->daddr.lsap = dsap;
244         memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
245         memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
246 
247         ev->type      = LLC_SAP_EV_TYPE_PRIM;
248         ev->prim      = LLC_TEST_PRIM;
249         ev->prim_type = LLC_PRIM_TYPE_REQ;
250         llc_sap_state_process(sap, skb);
251 }
252 
253 /**
254  *      llc_build_and_send_xid_pkt - XID interface for upper layers
255  *      @sap: sap to use
256  *      @skb: packet to send
257  *      @dmac: destination mac address
258  *      @dsap: destination sap
259  *
260  *      This function is called when upper layer wants to send a XID pdu.
261  *      Returns 0 for success, 1 otherwise.
262  */
263 void llc_build_and_send_xid_pkt(struct llc_sap *sap, struct sk_buff *skb,
264                                 u8 *dmac, u8 dsap)
265 {
266         struct llc_sap_state_ev *ev = llc_sap_ev(skb);
267 
268         ev->saddr.lsap = sap->laddr.lsap;
269         ev->daddr.lsap = dsap;
270         memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
271         memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
272 
273         ev->type      = LLC_SAP_EV_TYPE_PRIM;
274         ev->prim      = LLC_XID_PRIM;
275         ev->prim_type = LLC_PRIM_TYPE_REQ;
276         llc_sap_state_process(sap, skb);
277 }
278 
279 /**
280  *      llc_sap_rcv - sends received pdus to the sap state machine
281  *      @sap: current sap component structure.
282  *      @skb: received frame.
283  *
284  *      Sends received pdus to the sap state machine.
285  */
286 static void llc_sap_rcv(struct llc_sap *sap, struct sk_buff *skb,
287                         struct sock *sk)
288 {
289         struct llc_sap_state_ev *ev = llc_sap_ev(skb);
290 
291         ev->type   = LLC_SAP_EV_TYPE_PDU;
292         ev->reason = 0;
293         skb_orphan(skb);
294         sock_hold(sk);
295         skb->sk = sk;
296         skb->destructor = sock_efree;
297         llc_sap_state_process(sap, skb);
298 }
299 
300 static 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           ether_addr_equal(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  */
319 static 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         int slot = llc_sk_laddr_hashfn(sap, laddr);
325         struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];
326 
327         rcu_read_lock_bh();
328 again:
329         sk_nulls_for_each_rcu(rc, node, laddr_hb) {
330                 if (llc_dgram_match(sap, laddr, rc)) {
331                         /* Extra checks required by SLAB_DESTROY_BY_RCU */
332                         if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
333                                 goto again;
334                         if (unlikely(llc_sk(rc)->sap != sap ||
335                                      !llc_dgram_match(sap, laddr, rc))) {
336                                 sock_put(rc);
337                                 continue;
338                         }
339                         goto found;
340                 }
341         }
342         rc = NULL;
343         /*
344          * if the nulls value we got at the end of this lookup is
345          * not the expected one, we must restart lookup.
346          * We probably met an item that was moved to another chain.
347          */
348         if (unlikely(get_nulls_value(node) != slot))
349                 goto again;
350 found:
351         rcu_read_unlock_bh();
352         return rc;
353 }
354 
355 static inline bool llc_mcast_match(const struct llc_sap *sap,
356                                    const struct llc_addr *laddr,
357                                    const struct sk_buff *skb,
358                                    const struct sock *sk)
359 {
360      struct llc_sock *llc = llc_sk(sk);
361 
362      return sk->sk_type == SOCK_DGRAM &&
363           llc->laddr.lsap == laddr->lsap &&
364           llc->dev == skb->dev;
365 }
366 
367 static void llc_do_mcast(struct llc_sap *sap, struct sk_buff *skb,
368                          struct sock **stack, int count)
369 {
370         struct sk_buff *skb1;
371         int i;
372 
373         for (i = 0; i < count; i++) {
374                 skb1 = skb_clone(skb, GFP_ATOMIC);
375                 if (!skb1) {
376                         sock_put(stack[i]);
377                         continue;
378                 }
379 
380                 llc_sap_rcv(sap, skb1, stack[i]);
381                 sock_put(stack[i]);
382         }
383 }
384 
385 /**
386  *      llc_sap_mcast - Deliver multicast PDU's to all matching datagram sockets.
387  *      @sap: SAP
388  *      @laddr: address of local LLC (MAC + SAP)
389  *
390  *      Search socket list of the SAP and finds connections with same sap.
391  *      Deliver clone to each.
392  */
393 static void llc_sap_mcast(struct llc_sap *sap,
394                           const struct llc_addr *laddr,
395                           struct sk_buff *skb)
396 {
397         int i = 0, count = 256 / sizeof(struct sock *);
398         struct sock *sk, *stack[count];
399         struct llc_sock *llc;
400         struct hlist_head *dev_hb = llc_sk_dev_hash(sap, skb->dev->ifindex);
401 
402         spin_lock_bh(&sap->sk_lock);
403         hlist_for_each_entry(llc, dev_hb, dev_hash_node) {
404 
405                 sk = &llc->sk;
406 
407                 if (!llc_mcast_match(sap, laddr, skb, sk))
408                         continue;
409 
410                 sock_hold(sk);
411                 if (i < count)
412                         stack[i++] = sk;
413                 else {
414                         llc_do_mcast(sap, skb, stack, i);
415                         i = 0;
416                 }
417         }
418         spin_unlock_bh(&sap->sk_lock);
419 
420         llc_do_mcast(sap, skb, stack, i);
421 }
422 
423 
424 void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
425 {
426         struct llc_addr laddr;
427 
428         llc_pdu_decode_da(skb, laddr.mac);
429         llc_pdu_decode_dsap(skb, &laddr.lsap);
430 
431         if (is_multicast_ether_addr(laddr.mac)) {
432                 llc_sap_mcast(sap, &laddr, skb);
433                 kfree_skb(skb);
434         } else {
435                 struct sock *sk = llc_lookup_dgram(sap, &laddr);
436                 if (sk) {
437                         llc_sap_rcv(sap, skb, sk);
438                         sock_put(sk);
439                 } else
440                         kfree_skb(skb);
441         }
442 }
443 

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