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
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
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
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 */
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;
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;
131 s32 data_size;
132
133 if (skb->mac_len < ETH_HLEN)
134 return 0;
135
136 pdulen = eth_hdr(skb)->h_proto;
137 data_size = ntohs(pdulen) - llc_len;
138
139 if (data_size < 0 ||
140 !pskb_may_pull(skb, data_size))
141 return 0;
142 if (unlikely(pskb_trim_rcsum(skb, data_size)))
143 return 0;
144 }
145 return 1;
146 }
147
148 /**
149 * llc_rcv - 802.2 entry point from net lower layers
150 * @skb: received pdu
151 * @dev: device that receive pdu
152 * @pt: packet type
153 * @orig_dev: the original receive net device
154 *
155 * When the system receives a 802.2 frame this function is called. It
156 * checks SAP and connection of received pdu and passes frame to
157 * llc_{station,sap,conn}_rcv for sending to proper state machine. If
158 * the frame is related to a busy connection (a connection is sending
159 * data now), it queues this frame in the connection's backlog.
160 */
161 int llc_rcv(struct sk_buff *skb, struct net_device *dev,
162 struct packet_type *pt, struct net_device *orig_dev)
163 {
164 struct llc_sap *sap;
165 struct llc_pdu_sn *pdu;
166 int dest;
167 int (*rcv)(struct sk_buff *, struct net_device *,
168 struct packet_type *, struct net_device *);
169 void (*sta_handler)(struct sk_buff *skb);
170 void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb);
171
172 /*
173 * When the interface is in promisc. mode, drop all the crap that it
174 * receives, do not try to analyse it.
175 */
176 if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) {
177 dprintk("%s: PACKET_OTHERHOST\n", __func__);
178 goto drop;
179 }
180 skb = skb_share_check(skb, GFP_ATOMIC);
181 if (unlikely(!skb))
182 goto out;
183 if (unlikely(!llc_fixup_skb(skb)))
184 goto drop;
185 pdu = llc_pdu_sn_hdr(skb);
186 if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */
187 goto handle_station;
188 sap = llc_sap_find(pdu->dsap);
189 if (unlikely(!sap)) {/* unknown SAP */
190 dprintk("%s: llc_sap_find(%02X) failed!\n", __func__,
191 pdu->dsap);
192 goto drop;
193 }
194 /*
195 * First the upper layer protocols that don't need the full
196 * LLC functionality
197 */
198 rcv = rcu_dereference(sap->rcv_func);
199 dest = llc_pdu_type(skb);
200 sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL;
201 if (unlikely(!sap_handler)) {
202 if (rcv)
203 rcv(skb, dev, pt, orig_dev);
204 else
205 kfree_skb(skb);
206 } else {
207 if (rcv) {
208 struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC);
209 if (cskb)
210 rcv(cskb, dev, pt, orig_dev);
211 }
212 sap_handler(sap, skb);
213 }
214 llc_sap_put(sap);
215 out:
216 return 0;
217 drop:
218 kfree_skb(skb);
219 goto out;
220 handle_station:
221 sta_handler = READ_ONCE(llc_station_handler);
222 if (!sta_handler)
223 goto drop;
224 sta_handler(skb);
225 goto out;
226 }
227
228 EXPORT_SYMBOL(llc_add_pack);
229 EXPORT_SYMBOL(llc_remove_pack);
230 EXPORT_SYMBOL(llc_set_station_handler);
231
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