xref: /openbmc/linux/net/llc/llc_input.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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>
15 #include <net/llc.h>
16 #include <net/llc_pdu.h>
17 #include <net/llc_sap.h>
18 
19 #if 0
20 #define dprintk(args...) printk(KERN_DEBUG args)
21 #else
22 #define dprintk(args...)
23 #endif
24 
25 /*
26  * Packet handler for the station, registerable because in the minimal
27  * LLC core that is taking shape only the very minimal subset of LLC that
28  * is needed for things like IPX, Appletalk, etc will stay, with all the
29  * rest in the llc1 and llc2 modules.
30  */
31 static void (*llc_station_handler)(struct sk_buff *skb);
32 
33 /*
34  * Packet handlers for LLC_DEST_SAP and LLC_DEST_CONN.
35  */
36 static void (*llc_type_handlers[2])(struct llc_sap *sap,
37 				    struct sk_buff *skb);
38 
39 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
40 					    struct sk_buff *skb))
41 {
42 	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
43 		llc_type_handlers[type - 1] = handler;
44 }
45 
46 void llc_remove_pack(int type)
47 {
48 	if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
49 		llc_type_handlers[type - 1] = NULL;
50 }
51 
52 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
53 {
54 	llc_station_handler = handler;
55 }
56 
57 /**
58  *	llc_pdu_type - returns which LLC component must handle for PDU
59  *	@skb: input skb
60  *
61  *	This function returns which LLC component must handle this PDU.
62  */
63 static __inline__ int llc_pdu_type(struct sk_buff *skb)
64 {
65 	int type = LLC_DEST_CONN; /* I-PDU or S-PDU type */
66 	struct llc_pdu_sn *pdu = llc_pdu_sn_hdr(skb);
67 
68 	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) != LLC_PDU_TYPE_U)
69 		goto out;
70 	switch (LLC_U_PDU_CMD(pdu)) {
71 	case LLC_1_PDU_CMD_XID:
72 	case LLC_1_PDU_CMD_UI:
73 	case LLC_1_PDU_CMD_TEST:
74 		type = LLC_DEST_SAP;
75 		break;
76 	case LLC_2_PDU_CMD_SABME:
77 	case LLC_2_PDU_CMD_DISC:
78 	case LLC_2_PDU_RSP_UA:
79 	case LLC_2_PDU_RSP_DM:
80 	case LLC_2_PDU_RSP_FRMR:
81 		break;
82 	default:
83 		type = LLC_DEST_INVALID;
84 		break;
85 	}
86 out:
87 	return type;
88 }
89 
90 /**
91  *	llc_fixup_skb - initializes skb pointers
92  *	@skb: This argument points to incoming skb
93  *
94  *	Initializes internal skb pointer to start of network layer by deriving
95  *	length of LLC header; finds length of LLC control field in LLC header
96  *	by looking at the two lowest-order bits of the first control field
97  *	byte; field is either 3 or 4 bytes long.
98  */
99 static inline int llc_fixup_skb(struct sk_buff *skb)
100 {
101 	u8 llc_len = 2;
102 	struct llc_pdu_un *pdu;
103 
104 	if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
105 		return 0;
106 
107 	pdu = (struct llc_pdu_un *)skb->data;
108 	if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
109 		llc_len = 1;
110 	llc_len += 2;
111 
112 	if (unlikely(!pskb_may_pull(skb, llc_len)))
113 		return 0;
114 
115 	skb->transport_header += llc_len;
116 	skb_pull(skb, llc_len);
117 	if (skb->protocol == htons(ETH_P_802_2)) {
118 		__be16 pdulen = eth_hdr(skb)->h_proto;
119 		u16 data_size = ntohs(pdulen) - llc_len;
120 
121 		if (unlikely(pskb_trim_rcsum(skb, data_size)))
122 			return 0;
123 	}
124 	return 1;
125 }
126 
127 /**
128  *	llc_rcv - 802.2 entry point from net lower layers
129  *	@skb: received pdu
130  *	@dev: device that receive pdu
131  *	@pt: packet type
132  *
133  *	When the system receives a 802.2 frame this function is called. It
134  *	checks SAP and connection of received pdu and passes frame to
135  *	llc_{station,sap,conn}_rcv for sending to proper state machine. If
136  *	the frame is related to a busy connection (a connection is sending
137  *	data now), it queues this frame in the connection's backlog.
138  */
139 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
140 	    struct packet_type *pt, struct net_device *orig_dev)
141 {
142 	struct llc_sap *sap;
143 	struct llc_pdu_sn *pdu;
144 	int dest;
145 	int (*rcv)(struct sk_buff *, struct net_device *,
146 		   struct packet_type *, struct net_device *);
147 
148 	/*
149 	 * When the interface is in promisc. mode, drop all the crap that it
150 	 * receives, do not try to analyse it.
151 	 */
152 	if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
153 		dprintk("%s: PACKET_OTHERHOST\n", __FUNCTION__);
154 		goto drop;
155 	}
156 	skb = skb_share_check(skb, GFP_ATOMIC);
157 	if (unlikely(!skb))
158 		goto out;
159 	if (unlikely(!llc_fixup_skb(skb)))
160 		goto drop;
161 	pdu = llc_pdu_sn_hdr(skb);
162 	if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
163 	       goto handle_station;
164 	sap = llc_sap_find(pdu->dsap);
165 	if (unlikely(!sap)) {/* unknown SAP */
166 		dprintk("%s: llc_sap_find(%02X) failed!\n", __FUNCTION__,
167 			pdu->dsap);
168 		goto drop;
169 	}
170 	/*
171 	 * First the upper layer protocols that don't need the full
172 	 * LLC functionality
173 	 */
174 	rcv = rcu_dereference(sap->rcv_func);
175 	if (rcv) {
176 		struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
177 		if (cskb)
178 			rcv(cskb, dev, pt, orig_dev);
179 	}
180 	dest = llc_pdu_type(skb);
181 	if (unlikely(!dest || !llc_type_handlers[dest - 1]))
182 		goto drop_put;
183 	llc_type_handlers[dest - 1](sap, skb);
184 out_put:
185 	llc_sap_put(sap);
186 out:
187 	return 0;
188 drop:
189 	kfree_skb(skb);
190 	goto out;
191 drop_put:
192 	kfree_skb(skb);
193 	goto out_put;
194 handle_station:
195 	if (!llc_station_handler)
196 		goto drop;
197 	llc_station_handler(skb);
198 	goto out;
199 }
200 
201 EXPORT_SYMBOL(llc_add_pack);
202 EXPORT_SYMBOL(llc_remove_pack);
203 EXPORT_SYMBOL(llc_set_station_handler);
204