1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * em_canid.c Ematch rule to match CAN frames according to their CAN IDs
4 *
5 * Idea: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
6 * Copyright: (c) 2011 Czech Technical University in Prague
7 * (c) 2011 Volkswagen Group Research
8 * Authors: Michal Sojka <sojkam1@fel.cvut.cz>
9 * Pavel Pisa <pisa@cmp.felk.cvut.cz>
10 * Rostislav Lisovy <lisovy@gmail.cz>
11 * Funded by: Volkswagen Group Research
12 */
13
14 #include <linux/slab.h>
15 #include <linux/module.h>
16 #include <linux/types.h>
17 #include <linux/kernel.h>
18 #include <linux/string.h>
19 #include <linux/skbuff.h>
20 #include <net/pkt_cls.h>
21 #include <linux/can.h>
22
23 #define EM_CAN_RULES_MAX 500
24
25 struct canid_match {
26 /* For each SFF CAN ID (11 bit) there is one record in this bitfield */
27 DECLARE_BITMAP(match_sff, (1 << CAN_SFF_ID_BITS));
28
29 int rules_count;
30 int sff_rules_count;
31 int eff_rules_count;
32
33 /*
34 * Raw rules copied from netlink message; Used for sending
35 * information to userspace (when 'tc filter show' is invoked)
36 * AND when matching EFF frames
37 */
38 struct can_filter rules_raw[];
39 };
40
41 /**
42 * em_canid_get_id() - Extracts Can ID out of the sk_buff structure.
43 * @skb: buffer to extract Can ID from
44 */
45 static canid_t em_canid_get_id(struct sk_buff *skb)
46 {
47 /* CAN ID is stored within the data field */
48 struct can_frame *cf = (struct can_frame *)skb->data;
49
50 return cf->can_id;
51 }
52
53 static void em_canid_sff_match_add(struct canid_match *cm, u32 can_id,
54 u32 can_mask)
55 {
56 int i;
57
58 /*
59 * Limit can_mask and can_id to SFF range to
60 * protect against write after end of array
61 */
62 can_mask &= CAN_SFF_MASK;
63 can_id &= can_mask;
64
65 /* Single frame */
66 if (can_mask == CAN_SFF_MASK) {
67 set_bit(can_id, cm->match_sff);
68 return;
69 }
70
71 /* All frames */
72 if (can_mask == 0) {
73 bitmap_fill(cm->match_sff, (1 << CAN_SFF_ID_BITS));
74 return;
75 }
76
77 /*
78 * Individual frame filter.
79 * Add record (set bit to 1) for each ID that
80 * conforms particular rule
81 */
82 for (i = 0; i < (1 << CAN_SFF_ID_BITS); i++) {
83 if ((i & can_mask) == can_id)
84 set_bit(i, cm->match_sff);
85 }
86 }
87
88 static inline struct canid_match *em_canid_priv(struct tcf_ematch *m)
89 {
90 return (struct canid_match *)m->data;
91 }
92
93 static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m,
94 struct tcf_pkt_info *info)
95 {
96 struct canid_match *cm = em_canid_priv(m);
97 canid_t can_id;
98 int match = 0;
99 int i;
100 const struct can_filter *lp;
101
102 can_id = em_canid_get_id(skb);
103
104 if (can_id & CAN_EFF_FLAG) {
105 for (i = 0, lp = cm->rules_raw;
106 i < cm->eff_rules_count; i++, lp++) {
107 if (!(((lp->can_id ^ can_id) & lp->can_mask))) {
108 match = 1;
109 break;
110 }
111 }
112 } else { /* SFF */
113 can_id &= CAN_SFF_MASK;
114 match = (test_bit(can_id, cm->match_sff) ? 1 : 0);
115 }
116
117 return match;
118 }
119
120 static int em_canid_change(struct net *net, void *data, int len,
121 struct tcf_ematch *m)
122 {
123 struct can_filter *conf = data; /* Array with rules */
124 struct canid_match *cm;
125 int i;
126
127 if (!len)
128 return -EINVAL;
129
130 if (len % sizeof(struct can_filter))
131 return -EINVAL;
132
133 if (len > sizeof(struct can_filter) * EM_CAN_RULES_MAX)
134 return -EINVAL;
135
136 cm = kzalloc(sizeof(struct canid_match) + len, GFP_KERNEL);
137 if (!cm)
138 return -ENOMEM;
139
140 cm->rules_count = len / sizeof(struct can_filter);
141
142 /*
143 * We need two for() loops for copying rules into two contiguous
144 * areas in rules_raw to process all eff rules with a simple loop.
145 * NB: The configuration interface supports sff and eff rules.
146 * We do not support filters here that match for the same can_id
147 * provided in a SFF and EFF frame (e.g. 0x123 / 0x80000123).
148 * For this (unusual case) two filters have to be specified. The
149 * SFF/EFF separation is done with the CAN_EFF_FLAG in the can_id.
150 */
151
152 /* Fill rules_raw with EFF rules first */
153 for (i = 0; i < cm->rules_count; i++) {
154 if (conf[i].can_id & CAN_EFF_FLAG) {
155 memcpy(cm->rules_raw + cm->eff_rules_count,
156 &conf[i],
157 sizeof(struct can_filter));
158
159 cm->eff_rules_count++;
160 }
161 }
162
163 /* append SFF frame rules */
164 for (i = 0; i < cm->rules_count; i++) {
165 if (!(conf[i].can_id & CAN_EFF_FLAG)) {
166 memcpy(cm->rules_raw
167 + cm->eff_rules_count
168 + cm->sff_rules_count,
169 &conf[i], sizeof(struct can_filter));
170
171 cm->sff_rules_count++;
172
173 em_canid_sff_match_add(cm,
174 conf[i].can_id, conf[i].can_mask);
175 }
176 }
177
178 m->datalen = sizeof(struct canid_match) + len;
179 m->data = (unsigned long)cm;
180 return 0;
181 }
182
183 static void em_canid_destroy(struct tcf_ematch *m)
184 {
185 struct canid_match *cm = em_canid_priv(m);
186
187 kfree(cm);
188 }
189
190 static int em_canid_dump(struct sk_buff *skb, struct tcf_ematch *m)
191 {
192 struct canid_match *cm = em_canid_priv(m);
193
194 /*
195 * When configuring this ematch 'rules_count' is set not to exceed
196 * 'rules_raw' array size
197 */
198 if (nla_put_nohdr(skb, sizeof(struct can_filter) * cm->rules_count,
199 &cm->rules_raw) < 0)
200 return -EMSGSIZE;
201
202 return 0;
203 }
204
205 static struct tcf_ematch_ops em_canid_ops = {
206 .kind = TCF_EM_CANID,
207 .change = em_canid_change,
208 .match = em_canid_match,
209 .destroy = em_canid_destroy,
210 .dump = em_canid_dump,
211 .owner = THIS_MODULE,
212 .link = LIST_HEAD_INIT(em_canid_ops.link)
213 };
214
215 static int __init init_em_canid(void)
216 {
217 return tcf_em_register(&em_canid_ops);
218 }
219
220 static void __exit exit_em_canid(void)
221 {
222 tcf_em_unregister(&em_canid_ops);
223 }
224
225 MODULE_DESCRIPTION("ematch classifier to match CAN IDs embedded in skb CAN frames");
226 MODULE_LICENSE("GPL");
227
228 module_init(init_em_canid);
229 module_exit(exit_em_canid);
230
231 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID);
232
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