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, len: 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, len: 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 | * @orig_dev: the original receive net device |
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, |
156 | struct packet_type *pt, struct net_device *orig_dev) |
157 | { |
158 | struct llc_sap *sap; |
159 | struct llc_pdu_sn *pdu; |
160 | int dest; |
161 | int (*rcv)(struct sk_buff *, struct net_device *, |
162 | struct packet_type *, struct net_device *); |
163 | void (*sta_handler)(struct sk_buff *skb); |
164 | void (*sap_handler)(struct llc_sap *sap, struct sk_buff *skb); |
165 | |
166 | /* |
167 | * When the interface is in promisc. mode, drop all the crap that it |
168 | * receives, do not try to analyse it. |
169 | */ |
170 | if (unlikely(skb->pkt_type == PACKET_OTHERHOST)) { |
171 | dprintk("%s: PACKET_OTHERHOST\n" , __func__); |
172 | goto drop; |
173 | } |
174 | skb = skb_share_check(skb, GFP_ATOMIC); |
175 | if (unlikely(!skb)) |
176 | goto out; |
177 | if (unlikely(!llc_fixup_skb(skb))) |
178 | goto drop; |
179 | pdu = llc_pdu_sn_hdr(skb); |
180 | if (unlikely(!pdu->dsap)) /* NULL DSAP, refer to station */ |
181 | goto handle_station; |
182 | sap = llc_sap_find(sap_value: pdu->dsap); |
183 | if (unlikely(!sap)) {/* unknown SAP */ |
184 | dprintk("%s: llc_sap_find(%02X) failed!\n" , __func__, |
185 | pdu->dsap); |
186 | goto drop; |
187 | } |
188 | /* |
189 | * First the upper layer protocols that don't need the full |
190 | * LLC functionality |
191 | */ |
192 | rcv = rcu_dereference(sap->rcv_func); |
193 | dest = llc_pdu_type(skb); |
194 | sap_handler = dest ? READ_ONCE(llc_type_handlers[dest - 1]) : NULL; |
195 | if (unlikely(!sap_handler)) { |
196 | if (rcv) |
197 | rcv(skb, dev, pt, orig_dev); |
198 | else |
199 | kfree_skb(skb); |
200 | } else { |
201 | if (rcv) { |
202 | struct sk_buff *cskb = skb_clone(skb, GFP_ATOMIC); |
203 | if (cskb) |
204 | rcv(cskb, dev, pt, orig_dev); |
205 | } |
206 | sap_handler(sap, skb); |
207 | } |
208 | llc_sap_put(sap); |
209 | out: |
210 | return 0; |
211 | drop: |
212 | kfree_skb(skb); |
213 | goto out; |
214 | handle_station: |
215 | sta_handler = READ_ONCE(llc_station_handler); |
216 | if (!sta_handler) |
217 | goto drop; |
218 | sta_handler(skb); |
219 | goto out; |
220 | } |
221 | |
222 | EXPORT_SYMBOL(llc_add_pack); |
223 | EXPORT_SYMBOL(llc_remove_pack); |
224 | EXPORT_SYMBOL(llc_set_station_handler); |
225 | |