net/llc/llc_sap.c - kernel/msm - Gitiles

 /*
  * 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>

 /**
  *	llc_alloc_frame - allocates sk_buff for frame
  *	@dev: network device this skb will be sent over
  *
  *	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)
 {
 	struct sk_buff *skb = alloc_skb(128, GFP_ATOMIC);

 	if (skb) {
 		skb_reset_mac_header(skb);
 		skb_reserve(skb, 50);
 		skb_reset_network_header(skb);
 		skb->h.raw = skb->data;
 		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 llc_sap_state_ev *ev = llc_sap_ev(skb);

 	ev->type   = LLC_SAP_EV_TYPE_PDU;
 	ev->reason = 0;
 	llc_sap_state_process(sap, skb);
 }

 /**
  *	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_node *node;

 	read_lock_bh(&sap->sk_list.lock);
 	sk_for_each(rc, node, &sap->sk_list.list) {
 		struct llc_sock *llc = llc_sk(rc);

 		if (rc->sk_type == SOCK_DGRAM &&
 		    llc->laddr.lsap == laddr->lsap &&
 		    llc_mac_match(llc->laddr.mac, laddr->mac)) {
 			sock_hold(rc);
 			goto found;
 		}
 	}
 	rc = NULL;
 found:
 	read_unlock_bh(&sap->sk_list.lock);
 	return rc;
 }

 /**
  * 	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)
 {
 	struct sock *sk;
 	struct hlist_node *node;

 	read_lock_bh(&sap->sk_list.lock);
 	sk_for_each(sk, node, &sap->sk_list.list) {
 		struct llc_sock *llc = llc_sk(sk);
 		struct sk_buff *skb1;

 		if (sk->sk_type != SOCK_DGRAM)
 			continue;

 		if (llc->laddr.lsap != laddr->lsap)
 			continue;

 		if (llc->dev != skb->dev)
 			continue;

 		skb1 = skb_clone(skb, GFP_ATOMIC);
 		if (!skb1)
 			break;

 		sock_hold(sk);
 		skb_set_owner_r(skb1, sk);
 		llc_sap_rcv(sap, skb1);
 		sock_put(sk);
 	}
 	read_unlock_bh(&sap->sk_list.lock);
 }


 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 (llc_mac_multicast(laddr.mac)) {
 		llc_sap_mcast(sap, &laddr, skb);
 		kfree_skb(skb);
 	} else {
 		struct sock *sk = llc_lookup_dgram(sap, &laddr);
 		if (sk) {
 			skb_set_owner_r(skb, sk);
 			llc_sap_rcv(sap, skb);
 			sock_put(sk);
 		} else
 			kfree_skb(skb);
 	}
 }
	/*
	* 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>

	/**
	* llc_alloc_frame - allocates sk_buff for frame
	* @dev: network device this skb will be sent over
	*
	* 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)
	{
	struct sk_buff *skb = alloc_skb(128, GFP_ATOMIC);

	if (skb) {
	skb_reset_mac_header(skb);
	skb_reserve(skb, 50);
	skb_reset_network_header(skb);
	skb->h.raw = skb->data;
	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 llc_sap_state_ev *ev = llc_sap_ev(skb);

	ev->type = LLC_SAP_EV_TYPE_PDU;
	ev->reason = 0;
	llc_sap_state_process(sap, skb);
	}

	/**
	* 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_node *node;

	read_lock_bh(&sap->sk_list.lock);
	sk_for_each(rc, node, &sap->sk_list.list) {
	struct llc_sock *llc = llc_sk(rc);

	if (rc->sk_type == SOCK_DGRAM &&
	llc->laddr.lsap == laddr->lsap &&
	llc_mac_match(llc->laddr.mac, laddr->mac)) {
	sock_hold(rc);
	goto found;
	}
	}
	rc = NULL;
	found:
	read_unlock_bh(&sap->sk_list.lock);
	return rc;
	}

	/**
	* 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)
	{
	struct sock *sk;
	struct hlist_node *node;

	read_lock_bh(&sap->sk_list.lock);
	sk_for_each(sk, node, &sap->sk_list.list) {
	struct llc_sock *llc = llc_sk(sk);
	struct sk_buff *skb1;

	if (sk->sk_type != SOCK_DGRAM)
	continue;

	if (llc->laddr.lsap != laddr->lsap)
	continue;

	if (llc->dev != skb->dev)
	continue;

	skb1 = skb_clone(skb, GFP_ATOMIC);
	if (!skb1)
	break;

	sock_hold(sk);
	skb_set_owner_r(skb1, sk);
	llc_sap_rcv(sap, skb1);
	sock_put(sk);
	}
	read_unlock_bh(&sap->sk_list.lock);
	}


	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 (llc_mac_multicast(laddr.mac)) {
	llc_sap_mcast(sap, &laddr, skb);
	kfree_skb(skb);
	} else {
	struct sock *sk = llc_lookup_dgram(sap, &laddr);
	if (sk) {
	skb_set_owner_r(skb, sk);
	llc_sap_rcv(sap, skb);
	sock_put(sk);
	} else
	kfree_skb(skb);
	}
	}