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 <linux/slab.h>
16 #include <linux/export.h>
17 #include <net/net_namespace.h>
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
llc_add_pack(int type,void (* handler)(struct llc_sap * sap,struct sk_buff * skb))42 void llc_add_pack(int type, void (*handler)(struct llc_sap *sap,
43 struct sk_buff *skb))
44 {
45 smp_wmb(); /* ensure initialisation is complete before it's called */
46 if (type == LLC_DEST_SAP || type == LLC_DEST_CONN)
47 llc_type_handlers[type - 1] = handler;
48 }
49
llc_remove_pack(int type)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;
54 synchronize_net();
55 }
56
llc_set_station_handler(void (* handler)(struct sk_buff * skb))57 void llc_set_station_handler(void (*handler)(struct sk_buff *skb))
58 {
59 /* Ensure initialisation is complete before it's called */
60 if (handler)
61 smp_wmb();
62
63 llc_station_handler = handler;
64
65 if (!handler)
66 synchronize_net();
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 */
llc_pdu_type(struct sk_buff * skb)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 */
llc_fixup_skb(struct sk_buff * skb)111 static inline int llc_fixup_skb(struct sk_buff *skb)
112 {
113 u8 llc_len = 2;
114 struct llc_pdu_un *pdu;
115
116 if (unlikely(!pskb_may_pull(skb, sizeof(*pdu))))
117 return 0;
118
119 pdu = (struct llc_pdu_un *)skb->data;
120 if ((pdu->ctrl_1 & LLC_PDU_TYPE_MASK) == LLC_PDU_TYPE_U)
121 llc_len = 1;
122 llc_len += 2;
123
124 if (unlikely(!pskb_may_pull(skb, llc_len)))
125 return 0;
126
127 skb->transport_header += llc_len;
128 skb_pull(skb, llc_len);
129 if (skb->protocol == htons(ETH_P_802_2)) {
130 __be16 pdulen = eth_hdr(skb)->h_proto;
131 s32 data_size = ntohs(pdulen) - llc_len;
132
133 if (data_size < 0 ||
134 !pskb_may_pull(skb, data_size))
135 return 0;
136 if (unlikely(pskb_trim_rcsum(skb, data_size)))
137 return 0;
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
147 *
148 * When the system receives a 802.2 frame this function is called. It
149 * checks SAP and connection of received pdu and passes frame to
150 * llc_{station,sap,conn}_rcv for sending to proper state machine. If
151 * the frame is related to a busy connection (a connection is sending
152 * data now), it queues this frame in the connection's backlog.
153 */
llc_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt,struct net_device * orig_dev)154 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
155 struct packet_type *pt, struct net_device *orig_dev)
156 {
157 struct llc_sap *sap;
158 struct llc_pdu_sn *pdu;
159 int dest;
160 int (*rcv)(struct sk_buff *, struct net_device *,
161 struct packet_type *, struct net_device *);
162 void (*sta_handler)(struct sk_buff *skb);
163 void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);
164
165 if (!net_eq(dev_net(dev), &init_net))
166 goto drop;
167
168 /*
169 * When the interface is in promisc. mode, drop all the crap that it
170 * receives, do not try to analyse it.
171 */
172 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
173 dprintk("%s: PACKET_OTHERHOST\n", __func__);
174 goto drop;
175 }
176 skb = skb_share_check(skb, GFP_ATOMIC);
177 if (unlikely(!skb))
178 goto out;
179 if (unlikely(!llc_fixup_skb(skb)))
180 goto drop;
181 pdu = llc_pdu_sn_hdr(skb);
182 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
183 goto handle_station;
184 sap = llc_sap_find(pdu->dsap);
185 if (unlikely(!sap)) {/* unknown SAP */
186 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
187 pdu->dsap);
188 goto drop;
189 }
190 /*
191 * First the upper layer protocols that don't need the full
192 * LLC functionality
193 */
194 rcv = rcu_dereference(sap->rcv_func);
195 dest = llc_pdu_type(skb);
196 sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;
197 if (unlikely(!sap_handler)) {
198 if (rcv)
199 rcv(skb, dev, pt, orig_dev);
200 else
201 kfree_skb(skb);
202 } else {
203 if (rcv) {
204 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
205 if (cskb)
206 rcv(cskb, dev, pt, orig_dev);
207 }
208 sap_handler(sap, skb);
209 }
210 llc_sap_put(sap);
211 out:
212 return 0;
213 drop:
214 kfree_skb(skb);
215 goto out;
216 handle_station:
217 sta_handler = READ_ONCE(llc_station_handler);
218 if (!sta_handler)
219 goto drop;
220 sta_handler(skb);
221 goto out;
222 }
223
224 EXPORT_SYMBOL(llc_add_pack);
225 EXPORT_SYMBOL(llc_remove_pack);
226 EXPORT_SYMBOL(llc_set_station_handler);
227
