[linux-block.git] / net / llc / llc_input.c

/*
 * llc_input.c - Minimal input path for LLC
 *
 * 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 <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <net/net_namespace.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#include <net/llc_sap.h>

#if 0
#define dprintk(args...) printk(KERN_DEBUG args)
#else
#define dprintk(args...)
#endif

/*
 * Packet handler for the station, registerable because in the minimal
 * LLC core that is taking shape only the very minimal subset of LLC that
 * is needed for things like IPX, Appletalk, etc will stay, with all the
 * rest in the llc1 and llc2 modules.
 */
static void (*llc_station_handler)(struct sk_buff *skb);

/*
 * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
 */
static void (*llc_type_handlers[2])(struct llc_sap *sap,
				    struct sk_buff *skb);

void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
					    struct sk_buff *skb))
{
	smp_wmb(); /* ensure initialisation is complete before it's called */
	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
		llc_type_handlers[type - 1] = handler;
}

void llc_remove_pack(int type)
{
	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
		llc_type_handlers[type - 1] = NULL;
	synchronize_net();
}

void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
{
	/* Ensure initialisation is complete before it's called */
	if (handler)
		smp_wmb();

	llc_station_handler = handler;

	if (!handler)
		synchronize_net();
}

/**
 *	llc_pdu_type - returns which LLC component must handle for PDU
 *	@skb: input skb
 *
 *	This function returns which LLC component must handle this PDU.
 */
static __inline__ int llc_pdu_type(struct sk_buff *skb)
{
	int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);

	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
		goto out;
	switch (LLC_U_PDU_CMD(pdu)) {
	case LLC_1_PDU_CMD_XID:
	case LLC_1_PDU_CMD_UI:
	case LLC_1_PDU_CMD_TEST:
		type = LLC_DEST_SAP;
		break;
	case LLC_2_PDU_CMD_SABME:
	case LLC_2_PDU_CMD_DISC:
	case LLC_2_PDU_RSP_UA:
	case LLC_2_PDU_RSP_DM:
	case LLC_2_PDU_RSP_FRMR:
		break;
	default:
		type = LLC_DEST_INVALID;
		break;
	}
out:
	return type;
}

/**
 *	llc_fixup_skb - initializes skb pointers
 *	@skb: This argument points to incoming skb
 *
 *	Initializes internal skb pointer to start of network layer by deriving
 *	length of LLC header; finds length of LLC control field in LLC header
 *	by looking at the two lowest-order bits of the first control field
 *	byte; field is either 3 or 4 bytes long.
 */
static inline int llc_fixup_skb(struct sk_buff *skb)
{
	u8 llc_len = 2;
	struct llc_pdu_un *pdu;

	if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
		return 0;

	pdu = (struct llc_pdu_un *)skb->data;
	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
		llc_len = 1;
	llc_len += 2;

	if (unlikely(!pskb_may_pull(skb, llc_len)))
		return 0;

	skb->transport_header += llc_len;
	skb_pull(skb, llc_len);
	if (skb->protocol == htons(ETH_P_802_2)) {
		__be16 pdulen = eth_hdr(skb)->h_proto;
		s32 data_size = ntohs(pdulen) - llc_len;

		if (data_size < 0 ||
		    !pskb_may_pull(skb, data_size))
			return 0;
		if (unlikely(pskb_trim_rcsum(skb, data_size)))
			return 0;
	}
	return 1;
}

/**
 *	llc_rcv - 802.2 entry point from net lower layers
 *	@skb: received pdu
 *	@dev: device that receive pdu
 *	@pt: packet type
 *	@orig_dev: the original receive net device
 *
 *	When the system receives a 802.2 frame this function is called. It
 *	checks SAP and connection of received pdu and passes frame to
 *	llc_{station,sap,conn}_rcv for sending to proper state machine. If
 *	the frame is related to a busy connection (a connection is sending
 *	data now), it queues this frame in the connection's backlog.
 */
int llc_rcv(struct sk_buff *skb, struct net_device *dev,
	    struct packet_type *pt, struct net_device *orig_dev)
{
	struct llc_sap *sap;
	struct llc_pdu_sn *pdu;
	int dest;
	int (*rcv)(struct sk_buff *, struct net_device *,
		   struct packet_type *, struct net_device *);
	void (*sta_handler)(struct sk_buff *skb);
	void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);

	if (!net_eq(dev_net(dev), &init_net))
		goto drop;

	/*
	 * When the interface is in promisc. mode, drop all the crap that it
	 * receives, do not try to analyse it.
	 */
	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
		dprintk("%s: PACKET_OTHERHOST\n", __func__);
		goto drop;
	}
	skb = skb_share_check(skb, GFP_ATOMIC);
	if (unlikely(!skb))
		goto out;
	if (unlikely(!llc_fixup_skb(skb)))
		goto drop;
	pdu = llc_pdu_sn_hdr(skb);
	if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
	       goto handle_station;
	sap = llc_sap_find(pdu->dsap);
	if (unlikely(!sap)) {/* unknown SAP */
		dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
			pdu->dsap);
		goto drop;
	}
	/*
	 * First the upper layer protocols that don't need the full
	 * LLC functionality
	 */
	rcv = rcu_dereference(sap->rcv_func);
	dest = llc_pdu_type(skb);
	sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;
	if (unlikely(!sap_handler)) {
		if (rcv)
			rcv(skb, dev, pt, orig_dev);
		else
			kfree_skb(skb);
	} else {
		if (rcv) {
			struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
			if (cskb)
				rcv(cskb, dev, pt, orig_dev);
		}
		sap_handler(sap, skb);
	}
	llc_sap_put(sap);
out:
	return 0;
drop:
	kfree_skb(skb);
	goto out;
handle_station:
	sta_handler = READ_ONCE(llc_station_handler);
	if (!sta_handler)
		goto drop;
	sta_handler(skb);
	goto out;
}

EXPORT_SYMBOL(llc_add_pack);
EXPORT_SYMBOL(llc_remove_pack);
EXPORT_SYMBOL(llc_set_station_handler);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* llc_input.c - Minimal input path for 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/netdevice.h>
5a0e3ad6	15	#include <linux/slab.h>
bc3b2d7f	16	#include <linux/export.h>
e730c155	17	#include <net/net_namespace.h>
1da177e4 LT	18	#include <net/llc.h>
	19	#include <net/llc_pdu.h>
	20	#include <net/llc_sap.h>
	21
	22	#if 0
	23	#define dprintk(args...) printk(KERN_DEBUG args)
	24	#else
	25	#define dprintk(args...)
	26	#endif
	27
	28	/*
	29	* Packet handler for the station, registerable because in the minimal
	30	* LLC core that is taking shape only the very minimal subset of LLC that
	31	* is needed for things like IPX, Appletalk, etc will stay, with all the
	32	* rest in the llc1 and llc2 modules.
	33	*/
	34	static void (llc_station_handler)(struct sk_buff skb);
	35
	36	/*
	37	* Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
	38	*/
	39	static void (llc_type_handlers[2])(struct llc_sap sap,
	40	struct sk_buff *skb);
	41
	42	void llc_add_pack(int type, void (handler)(struct llc_sap sap,
	43	struct sk_buff *skb))
	44	{
aadf31de	45	smp_wmb(); /* ensure initialisation is complete before it's called */
1da177e4 LT	46	if (type == LLC_DEST_SAP \|\| type == LLC_DEST_CONN)
	47	llc_type_handlers[type - 1] = handler;
	48	}
	49
	50	void llc_remove_pack(int type)
	51	{
	52	if (type == LLC_DEST_SAP \|\| type == LLC_DEST_CONN)
	53	llc_type_handlers[type - 1] = NULL;
aadf31de	54	synchronize_net();
1da177e4 LT	55	}
	56
	57	void llc_set_station_handler(void (handler)(struct sk_buff skb))
	58	{
aadf31de BH	59	/* Ensure initialisation is complete before it's called */
	60	if (handler)
	61	smp_wmb();
	62
1da177e4	63	llc_station_handler = handler;
aadf31de BH	64
	65	if (!handler)
	66	synchronize_net();
1da177e4 LT	67	}
	68
	69	/**
	70	* llc_pdu_type - returns which LLC component must handle for PDU
	71	* @skb: input skb
	72	*
	73	* This function returns which LLC component must handle this PDU.
	74	*/
	75	static __inline__ int llc_pdu_type(struct sk_buff *skb)
	76	{
	77	int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
	78	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
	79
	80	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
	81	goto out;
	82	switch (LLC_U_PDU_CMD(pdu)) {
	83	case LLC_1_PDU_CMD_XID:
	84	case LLC_1_PDU_CMD_UI:
	85	case LLC_1_PDU_CMD_TEST:
	86	type = LLC_DEST_SAP;
	87	break;
	88	case LLC_2_PDU_CMD_SABME:
	89	case LLC_2_PDU_CMD_DISC:
	90	case LLC_2_PDU_RSP_UA:
	91	case LLC_2_PDU_RSP_DM:
	92	case LLC_2_PDU_RSP_FRMR:
	93	break;
	94	default:
	95	type = LLC_DEST_INVALID;
	96	break;
	97	}
	98	out:
	99	return type;
	100	}
	101
	102	/**
	103	* llc_fixup_skb - initializes skb pointers
	104	* @skb: This argument points to incoming skb
	105	*
	106	* Initializes internal skb pointer to start of network layer by deriving
	107	* length of LLC header; finds length of LLC control field in LLC header
	108	* by looking at the two lowest-order bits of the first control field
	109	* byte; field is either 3 or 4 bytes long.
	110	*/
	111	static inline int llc_fixup_skb(struct sk_buff *skb)
	112	{
	113	u8 llc_len = 2;
096f0eb1	114	struct llc_pdu_un *pdu;
1da177e4	115
af426d32	116	if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
1da177e4 LT	117	return 0;
1da177e4 LT	118
096f0eb1	119	pdu = (struct llc_pdu_un *)skb->data;
1da177e4 LT	120	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
	121	llc_len = 1;
	122	llc_len += 2;
096f0eb1 JF	123
	124	if (unlikely(!pskb_may_pull(skb, llc_len)))
	125	return 0;
	126
b0e380b1	127	skb->transport_header += llc_len;
1da177e4 LT	128	skb_pull(skb, llc_len);
1da177e4 LT	129	if (skb->protocol == htons(ETH_P_802_2)) {
3fbd418a	130	__be16 pdulen = eth_hdr(skb)->h_proto;
27785d83	131	s32 data_size = ntohs(pdulen) - llc_len;
1da177e4	132
27785d83	133	if (data_size < 0 \|\|
aa867359	134	!pskb_may_pull(skb, data_size))
27785d83	135	return 0;
5185db09 DM	136	if (unlikely(pskb_trim_rcsum(skb, data_size)))
5185db09 DM	137	return 0;
1da177e4 LT	138	}
	139	return 1;
	140	}
	141
	142	/**
	143	* llc_rcv - 802.2 entry point from net lower layers
	144	* @skb: received pdu
	145	* @dev: device that receive pdu
	146	* @pt: packet type
74c950c9	147	* @orig_dev: the original receive net device
1da177e4 LT	148	*
	149	* When the system receives a 802.2 frame this function is called. It
	150	* checks SAP and connection of received pdu and passes frame to
	151	* llc_{station,sap,conn}_rcv for sending to proper state machine. If
	152	* the frame is related to a busy connection (a connection is sending
	153	* data now), it queues this frame in the connection's backlog.
	154	*/
	155	int llc_rcv(struct sk_buff skb, struct net_device dev,
f2ccd8fa	156	struct packet_type pt, struct net_device orig_dev)
1da177e4 LT	157	{
	158	struct llc_sap *sap;
	159	struct llc_pdu_sn *pdu;
	160	int dest;
23dbe791 SH	161	int (rcv)(struct sk_buff , struct net_device *,
23dbe791 SH	162	struct packet_type , struct net_device );
aadf31de BH	163	void (sta_handler)(struct sk_buff skb);
aadf31de BH	164	void (sap_handler)(struct llc_sap sap, struct sk_buff *skb);
1da177e4	165
721499e8	166	if (!net_eq(dev_net(dev), &init_net))
e730c155 EB	167	goto drop;
e730c155 EB	168
1da177e4 LT	169	/*
	170	* When the interface is in promisc. mode, drop all the crap that it
	171	* receives, do not try to analyse it.
	172	*/
	173	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
0dc47877	174	dprintk("%s: PACKET_OTHERHOST\n", __func__);
1da177e4 LT	175	goto drop;
	176	}
	177	skb = skb_share_check(skb, GFP_ATOMIC);
	178	if (unlikely(!skb))
	179	goto out;
	180	if (unlikely(!llc_fixup_skb(skb)))
	181	goto drop;
	182	pdu = llc_pdu_sn_hdr(skb);
	183	if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
	184	goto handle_station;
	185	sap = llc_sap_find(pdu->dsap);
	186	if (unlikely(!sap)) {/* unknown SAP */
0dc47877	187	dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
d57b1869	188	pdu->dsap);
1da177e4 LT	189	goto drop;
	190	}
	191	/*
	192	* First the upper layer protocols that don't need the full
	193	* LLC functionality
	194	*/
23dbe791	195	rcv = rcu_dereference(sap->rcv_func);
1da177e4	196	dest = llc_pdu_type(skb);
6aa7de05	197	sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;
aadf31de	198	if (unlikely(!sap_handler)) {
696ea472 CG	199	if (rcv)
	200	rcv(skb, dev, pt, orig_dev);
	201	else
	202	kfree_skb(skb);
	203	} else {
	204	if (rcv) {
	205	struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
	206	if (cskb)
	207	rcv(cskb, dev, pt, orig_dev);
	208	}
aadf31de	209	sap_handler(sap, skb);
696ea472	210	}
6e2144b7	211	llc_sap_put(sap);
1da177e4 LT	212	out:
	213	return 0;
	214	drop:
	215	kfree_skb(skb);
	216	goto out;
	217	handle_station:
6aa7de05	218	sta_handler = READ_ONCE(llc_station_handler);
aadf31de	219	if (!sta_handler)
1da177e4	220	goto drop;
aadf31de	221	sta_handler(skb);
1da177e4 LT	222	goto out;
	223	}
	224
	225	EXPORT_SYMBOL(llc_add_pack);
	226	EXPORT_SYMBOL(llc_remove_pack);
	227	EXPORT_SYMBOL(llc_set_station_handler);