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
  28static 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 */
  47struct 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
  69void 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 */
  91void 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 */
 116static 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 */
 144static 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        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 */
 166static 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;
 188out:
 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 */
 201static 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 */
 237void 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 */
 263void 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 */
 286static 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->sk = sk;
 294        llc_sap_state_process(sap, skb);
 295}
 296
 297static inline bool llc_dgram_match(const struct llc_sap *sap,
 298                                   const struct llc_addr *laddr,
 299                                   const struct sock *sk)
 300{
 301     struct llc_sock *llc = llc_sk(sk);
 302
 303     return sk->sk_type == SOCK_DGRAM &&
 304          llc->laddr.lsap == laddr->lsap &&
 305          llc_mac_match(llc->laddr.mac, laddr->mac);
 306}
 307
 308/**
 309 *      llc_lookup_dgram - Finds dgram socket for the local sap/mac
 310 *      @sap: SAP
 311 *      @laddr: address of local LLC (MAC + SAP)
 312 *
 313 *      Search socket list of the SAP and finds connection using the local
 314 *      mac, and local sap. Returns pointer for socket found, %NULL otherwise.
 315 */
 316static struct sock *llc_lookup_dgram(struct llc_sap *sap,
 317                                     const struct llc_addr *laddr)
 318{
 319        struct sock *rc;
 320        struct hlist_nulls_node *node;
 321        int slot = llc_sk_laddr_hashfn(sap, laddr);
 322        struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];
 323
 324        rcu_read_lock_bh();
 325again:
 326        sk_nulls_for_each_rcu(rc, node, laddr_hb) {
 327                if (llc_dgram_match(sap, laddr, rc)) {
 328                        /* Extra checks required by SLAB_DESTROY_BY_RCU */
 329                        if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
 330                                goto again;
 331                        if (unlikely(llc_sk(rc)->sap != sap ||
 332                                     !llc_dgram_match(sap, laddr, rc))) {
 333                                sock_put(rc);
 334                                continue;
 335                        }
 336                        goto found;
 337                }
 338        }
 339        rc = NULL;
 340        /*
 341         * if the nulls value we got at the end of this lookup is
 342         * not the expected one, we must restart lookup.
 343         * We probably met an item that was moved to another chain.
 344         */
 345        if (unlikely(get_nulls_value(node) != slot))
 346                goto again;
 347found:
 348        rcu_read_unlock_bh();
 349        return rc;
 350}
 351
 352static inline bool llc_mcast_match(const struct llc_sap *sap,
 353                                   const struct llc_addr *laddr,
 354                                   const struct sk_buff *skb,
 355                                   const struct sock *sk)
 356{
 357     struct llc_sock *llc = llc_sk(sk);
 358
 359     return sk->sk_type == SOCK_DGRAM &&
 360          llc->laddr.lsap == laddr->lsap &&
 361          llc->dev == skb->dev;
 362}
 363
 364static void llc_do_mcast(struct llc_sap *sap, struct sk_buff *skb,
 365                         struct sock **stack, int count)
 366{
 367        struct sk_buff *skb1;
 368        int i;
 369
 370        for (i = 0; i < count; i++) {
 371                skb1 = skb_clone(skb, GFP_ATOMIC);
 372                if (!skb1) {
 373                        sock_put(stack[i]);
 374                        continue;
 375                }
 376
 377                llc_sap_rcv(sap, skb1, stack[i]);
 378                sock_put(stack[i]);
 379        }
 380}
 381
 382/**
 383 *      llc_sap_mcast - Deliver multicast PDU's to all matching datagram sockets.
 384 *      @sap: SAP
 385 *      @laddr: address of local LLC (MAC + SAP)
 386 *
 387 *      Search socket list of the SAP and finds connections with same sap.
 388 *      Deliver clone to each.
 389 */
 390static void llc_sap_mcast(struct llc_sap *sap,
 391                          const struct llc_addr *laddr,
 392                          struct sk_buff *skb)
 393{
 394        int i = 0, count = 256 / sizeof(struct sock *);
 395        struct sock *sk, *stack[count];
 396        struct hlist_node *node;
 397        struct llc_sock *llc;
 398        struct hlist_head *dev_hb = llc_sk_dev_hash(sap, skb->dev->ifindex);
 399
 400        spin_lock_bh(&sap->sk_lock);
 401        hlist_for_each_entry(llc, node, dev_hb, dev_hash_node) {
 402
 403                sk = &llc->sk;
 404
 405                if (!llc_mcast_match(sap, laddr, skb, sk))
 406                        continue;
 407
 408                sock_hold(sk);
 409                if (i < count)
 410                        stack[i++] = sk;
 411                else {
 412                        llc_do_mcast(sap, skb, stack, i);
 413                        i = 0;
 414                }
 415        }
 416        spin_unlock_bh(&sap->sk_lock);
 417
 418        llc_do_mcast(sap, skb, stack, i);
 419}
 420
 421
 422void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
 423{
 424        struct llc_addr laddr;
 425
 426        llc_pdu_decode_da(skb, laddr.mac);
 427        llc_pdu_decode_dsap(skb, &laddr.lsap);
 428
 429        if (llc_mac_multicast(laddr.mac)) {
 430                llc_sap_mcast(sap, &laddr, skb);
 431                kfree_skb(skb);
 432        } else {
 433                struct sock *sk = llc_lookup_dgram(sap, &laddr);
 434                if (sk) {
 435                        llc_sap_rcv(sap, skb, sk);
 436                        sock_put(sk);
 437                } else
 438                        kfree_skb(skb);
 439        }
 440}
 441
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