text: /*
   * llc_sap.c - driver routines for SAP component.
   *
   * Copyright (c) 1997 by Procom Technology, Inc.
   * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   *
   * This program can be redistributed or modified under the terms of the
   * GNU General Public License as published by the Free Software Foundation.
   * This program is distributed without any warranty or implied warranty
   * of merchantability or fitness for a particular purpose.
   *
   * See the GNU General Public License for more details.
   */
  
  #include <net/llc.h>
  #include <net/llc_if.h>
  #include <net/llc_conn.h>
  #include <net/llc_pdu.h>
  #include <net/llc_sap.h>
  #include <net/llc_s_ac.h>
  #include <net/llc_s_ev.h>
  #include <net/llc_s_st.h>
  #include <net/sock.h>
  #include <net/tcp_states.h>
  #include <linux/llc.h>
  #include <linux/slab.h>
  
  static int llc_mac_header_len(unsigned short devtype)
  {
  	switch (devtype) {
  	case ARPHRD_ETHER:
  	case ARPHRD_LOOPBACK:
  		return sizeof(struct ethhdr);
  	}
  	return 0;
  }
  
  /**
   *	llc_alloc_frame - allocates sk_buff for frame
   *	@dev: network device this skb will be sent over
   *	@type: pdu type to allocate
   *	@data_size: data size to allocate
   *
   *	Allocates an sk_buff for frame and initializes sk_buff fields.
   *	Returns allocated skb or %NULL when out of memory.
   */
  struct sk_buff *llc_alloc_frame(struct sock *sk, struct net_device *dev,
  				u8 type, u32 data_size)
  {
  	int hlen = type == LLC_PDU_TYPE_U ? 3 : 4;
  	struct sk_buff *skb;
  
  	hlen += llc_mac_header_len(dev->type);
  	skb = alloc_skb(hlen + data_size, GFP_ATOMIC);
  
  	if (skb) {
  		skb_reset_mac_header(skb);
  		skb_reserve(skb, hlen);
  		skb_reset_network_header(skb);
  		skb_reset_transport_header(skb);
  		skb->protocol = htons(ETH_P_802_2);
  		skb->dev      = dev;
  		if (sk != NULL)
  			skb_set_owner_w(skb, sk);
  	}
  	return skb;
  }
  
  void llc_save_primitive(struct sock *sk, struct sk_buff *skb, u8 prim)
  {
  	struct sockaddr_llc *addr;
  
         /* save primitive for use by the user. */
  	addr		  = llc_ui_skb_cb(skb);
  
  	memset(addr, 0, sizeof(*addr));
  	addr->sllc_family = sk->sk_family;
  	addr->sllc_arphrd = skb->dev->type;
  	addr->sllc_test   = prim == LLC_TEST_PRIM;
  	addr->sllc_xid    = prim == LLC_XID_PRIM;
  	addr->sllc_ua     = prim == LLC_DATAUNIT_PRIM;
  	llc_pdu_decode_sa(skb, addr->sllc_mac);
  	llc_pdu_decode_ssap(skb, &addr->sllc_sap);
  }
  
  /**
   *	llc_sap_rtn_pdu - Informs upper layer on rx of an UI, XID or TEST pdu.
   *	@sap: pointer to SAP
   *	@skb: received pdu
   */
  void llc_sap_rtn_pdu(struct llc_sap *sap, struct sk_buff *skb)
  {
  	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
  	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
  
  	switch (LLC_U_PDU_RSP(pdu)) {
  	case LLC_1_PDU_CMD_TEST:
  		ev->prim = LLC_TEST_PRIM;	break;
  	case LLC_1_PDU_CMD_XID:
  		ev->prim = LLC_XID_PRIM;	break;
  	case LLC_1_PDU_CMD_UI:
  		ev->prim = LLC_DATAUNIT_PRIM;	break;
  	}
  	ev->ind_cfm_flag = LLC_IND;
  }
  
  /**
   *	llc_find_sap_trans - finds transition for event
   *	@sap: pointer to SAP
   *	@skb: happened event
   *
   *	This function finds transition that matches with happened event.
   *	Returns the pointer to found transition on success or %NULL for
   *	failure.
   */
  static struct llc_sap_state_trans *llc_find_sap_trans(struct llc_sap *sap,
  						      struct sk_buff *skb)
  {
  	int i = 0;
  	struct llc_sap_state_trans *rc = NULL;
  	struct llc_sap_state_trans **next_trans;
  	struct llc_sap_state *curr_state = &llc_sap_state_table[sap->state - 1];
  	/*
  	 * Search thru events for this state until list exhausted or until
  	 * its obvious the event is not valid for the current state
  	 */
  	for (next_trans = curr_state->transitions; next_trans[i]->ev; i++)
  		if (!next_trans[i]->ev(sap, skb)) {
  			rc = next_trans[i]; /* got event match; return it */
  			break;
  		}
  	return rc;
  }
  
  /**
   *	llc_exec_sap_trans_actions - execute actions related to event
   *	@sap: pointer to SAP
   *	@trans: pointer to transition that it's actions must be performed
   *	@skb: happened event.
   *
   *	This function executes actions that is related to happened event.
   *	Returns 0 for success and 1 for failure of at least one action.
   */
  static int llc_exec_sap_trans_actions(struct llc_sap *sap,
  				      struct llc_sap_state_trans *trans,
  				      struct sk_buff *skb)
  {
  	int rc = 0;
  	llc_sap_action_t *next_action = trans->ev_actions;
  
  	for (; next_action && *next_action; next_action++)
  		if ((*next_action)(sap, skb))
  			rc = 1;
  	return rc;
  }
  
  /**
   *	llc_sap_next_state - finds transition, execs actions & change SAP state
   *	@sap: pointer to SAP
   *	@skb: happened event
   *
   *	This function finds transition that matches with happened event, then
   *	executes related actions and finally changes state of SAP. It returns
   *	0 on success and 1 for failure.
   */
  static int llc_sap_next_state(struct llc_sap *sap, struct sk_buff *skb)
  {
  	int rc = 1;
  	struct llc_sap_state_trans *trans;
  
  	if (sap->state > LLC_NR_SAP_STATES)
  		goto out;
  	trans = llc_find_sap_trans(sap, skb);
  	if (!trans)
  		goto out;
  	/*
  	 * Got the state to which we next transition; perform the actions
  	 * associated with this transition before actually transitioning to the
  	 * next state
  	 */
  	rc = llc_exec_sap_trans_actions(sap, trans, skb);
  	if (rc)
  		goto out;
  	/*
  	 * Transition SAP to next state if all actions execute successfully
  	 */
  	sap->state = trans->next_state;
  out:
  	return rc;
  }
  
  /**
   *	llc_sap_state_process - sends event to SAP state machine
   *	@sap: sap to use
   *	@skb: pointer to occurred event
   *
   *	After executing actions of the event, upper layer will be indicated
   *	if needed(on receiving an UI frame). sk can be null for the
   *	datalink_proto case.
   */
  static void llc_sap_state_process(struct llc_sap *sap, struct sk_buff *skb)
  {
  	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
  
  	/*
  	 * We have to hold the skb, because llc_sap_next_state
  	 * will kfree it in the sending path and we need to
  	 * look at the skb->cb, where we encode llc_sap_state_ev.
  	 */
  	skb_get(skb);
  	ev->ind_cfm_flag = 0;
  	llc_sap_next_state(sap, skb);
  	if (ev->ind_cfm_flag == LLC_IND) {
  		if (skb->sk->sk_state == TCP_LISTEN)
  			kfree_skb(skb);
  		else {
  			llc_save_primitive(skb->sk, skb, ev->prim);
  
  			/* queue skb to the user. */
  			if (sock_queue_rcv_skb(skb->sk, skb))
  				kfree_skb(skb);
  		}
  	}
  	kfree_skb(skb);
  }
  
  /**
   *	llc_build_and_send_test_pkt - TEST interface for upper layers.
   *	@sap: sap to use
   *	@skb: packet to send
   *	@dmac: destination mac address
   *	@dsap: destination sap
   *
   *	This function is called when upper layer wants to send a TEST pdu.
   *	Returns 0 for success, 1 otherwise.
   */
  void llc_build_and_send_test_pkt(struct llc_sap *sap,
  				 struct sk_buff *skb, u8 *dmac, u8 dsap)
  {
  	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
  
  	ev->saddr.lsap = sap->laddr.lsap;
  	ev->daddr.lsap = dsap;
  	memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
  	memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
  
  	ev->type      = LLC_SAP_EV_TYPE_PRIM;
  	ev->prim      = LLC_TEST_PRIM;
  	ev->prim_type = LLC_PRIM_TYPE_REQ;
  	llc_sap_state_process(sap, skb);
  }
  
  /**
   *	llc_build_and_send_xid_pkt - XID interface for upper layers
   *	@sap: sap to use
   *	@skb: packet to send
   *	@dmac: destination mac address
   *	@dsap: destination sap
   *
   *	This function is called when upper layer wants to send a XID pdu.
   *	Returns 0 for success, 1 otherwise.
   */
  void llc_build_and_send_xid_pkt(struct llc_sap *sap, struct sk_buff *skb,
  				u8 *dmac, u8 dsap)
  {
  	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
  
  	ev->saddr.lsap = sap->laddr.lsap;
  	ev->daddr.lsap = dsap;
  	memcpy(ev->saddr.mac, skb->dev->dev_addr, IFHWADDRLEN);
  	memcpy(ev->daddr.mac, dmac, IFHWADDRLEN);
  
  	ev->type      = LLC_SAP_EV_TYPE_PRIM;
  	ev->prim      = LLC_XID_PRIM;
  	ev->prim_type = LLC_PRIM_TYPE_REQ;
  	llc_sap_state_process(sap, skb);
  }
  
  /**
   *	llc_sap_rcv - sends received pdus to the sap state machine
   *	@sap: current sap component structure.
   *	@skb: received frame.
   *
   *	Sends received pdus to the sap state machine.
   */
  static void llc_sap_rcv(struct llc_sap *sap, struct sk_buff *skb,
  			struct sock *sk)
  {
  	struct llc_sap_state_ev *ev = llc_sap_ev(skb);
  
  	ev->type   = LLC_SAP_EV_TYPE_PDU;
  	ev->reason = 0;
  	skb->sk = sk;
  	llc_sap_state_process(sap, skb);
  }
  
  static inline bool llc_dgram_match(const struct llc_sap *sap,
  				   const struct llc_addr *laddr,
  				   const struct sock *sk)
  {
       struct llc_sock *llc = llc_sk(sk);
  
       return sk->sk_type == SOCK_DGRAM &&
  	  llc->laddr.lsap == laddr->lsap &&
  	  ether_addr_equal(llc->laddr.mac, laddr->mac);
  }
  
  /**
   *	llc_lookup_dgram - Finds dgram socket for the local sap/mac
   *	@sap: SAP
   *	@laddr: address of local LLC (MAC + SAP)
   *
   *	Search socket list of the SAP and finds connection using the local
   *	mac, and local sap. Returns pointer for socket found, %NULL otherwise.
   */
  static struct sock *llc_lookup_dgram(struct llc_sap *sap,
  				     const struct llc_addr *laddr)
  {
  	struct sock *rc;
  	struct hlist_nulls_node *node;
  	int slot = llc_sk_laddr_hashfn(sap, laddr);
  	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];
  
  	rcu_read_lock_bh();
  again:
  	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
  		if (llc_dgram_match(sap, laddr, rc)) {
  			/* Extra checks required by SLAB_DESTROY_BY_RCU */
  			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
  				goto again;
  			if (unlikely(llc_sk(rc)->sap != sap ||
  				     !llc_dgram_match(sap, laddr, rc))) {
  				sock_put(rc);
  				continue;
  			}
  			goto found;
  		}
  	}
  	rc = NULL;
  	/*
  	 * if the nulls value we got at the end of this lookup is
  	 * not the expected one, we must restart lookup.
  	 * We probably met an item that was moved to another chain.
  	 */
  	if (unlikely(get_nulls_value(node) != slot))
  		goto again;
  found:
  	rcu_read_unlock_bh();
  	return rc;
  }
  
  static inline bool llc_mcast_match(const struct llc_sap *sap,
  				   const struct llc_addr *laddr,
  				   const struct sk_buff *skb,
  				   const struct sock *sk)
  {
       struct llc_sock *llc = llc_sk(sk);
  
       return sk->sk_type == SOCK_DGRAM &&
  	  llc->laddr.lsap == laddr->lsap &&
  	  llc->dev == skb->dev;
  }
  
  static void llc_do_mcast(struct llc_sap *sap, struct sk_buff *skb,
  			 struct sock **stack, int count)
  {
  	struct sk_buff *skb1;
  	int i;
  
  	for (i = 0; i < count; i++) {
  		skb1 = skb_clone(skb, GFP_ATOMIC);
  		if (!skb1) {
  			sock_put(stack[i]);
  			continue;
  		}
  
  		llc_sap_rcv(sap, skb1, stack[i]);
  		sock_put(stack[i]);
  	}
  }
  
  /**
   * 	llc_sap_mcast - Deliver multicast PDU's to all matching datagram sockets.
   *	@sap: SAP
   *	@laddr: address of local LLC (MAC + SAP)
   *
   *	Search socket list of the SAP and finds connections with same sap.
   *	Deliver clone to each.
   */
  static void llc_sap_mcast(struct llc_sap *sap,
  			  const struct llc_addr *laddr,
  			  struct sk_buff *skb)
  {
  	int i = 0, count = 256 / sizeof(struct sock *);
  	struct sock *sk, *stack[count];
  	struct llc_sock *llc;
  	struct hlist_head *dev_hb = llc_sk_dev_hash(sap, skb->dev->ifindex);
  
  	spin_lock_bh(&sap->sk_lock);
  	hlist_for_each_entry(llc, dev_hb, dev_hash_node) {
  
  		sk = &llc->sk;
  
  		if (!llc_mcast_match(sap, laddr, skb, sk))
  			continue;
  
  		sock_hold(sk);
  		if (i < count)
  			stack[i++] = sk;
  		else {
  			llc_do_mcast(sap, skb, stack, i);
  			i = 0;
  		}
  	}
  	spin_unlock_bh(&sap->sk_lock);
  
  	llc_do_mcast(sap, skb, stack, i);
  }
  
  
  void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb)
  {
  	struct llc_addr laddr;
  
  	llc_pdu_decode_da(skb, laddr.mac);
  	llc_pdu_decode_dsap(skb, &laddr.lsap);
  
  	if (is_multicast_ether_addr(laddr.mac)) {
  		llc_sap_mcast(sap, &laddr, skb);
  		kfree_skb(skb);
  	} else {
  		struct sock *sk = llc_lookup_dgram(sap, &laddr);
  		if (sk) {
  			llc_sap_rcv(sap, skb, sk);
  			sock_put(sk);
  		} else
  			kfree_skb(skb);
  	}
  }
  