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 if (!pskb_may_pull(skb, CAN_MTU)) 103 return 0; 104 105 can_id = em_canid_get_id(skb); 106 107 if (can_id & CAN_EFF_FLAG) { 108 for (i = 0, lp = cm->rules_raw; 109 i < cm->eff_rules_count; i++, lp++) { 110 if (!(((lp->can_id ^ can_id) & lp->can_mask))) { 111 match = 1; 112 break; 113 } 114 } 115 } else { /* SFF */ 116 can_id &= CAN_SFF_MASK; 117 match = (test_bit(can_id, cm->match_sff) ? 1 : 0); 118 } 119 120 return match; 121 } 122 123 static int em_canid_change(struct net *net, void *data, int len, 124 struct tcf_ematch *m) 125 { 126 struct can_filter *conf = data; /* Array with rules */ 127 struct canid_match *cm; 128 int i; 129 130 if (!len) 131 return -EINVAL; 132 133 if (len % sizeof(struct can_filter)) 134 return -EINVAL; 135 136 if (len > sizeof(struct can_filter) * EM_CAN_RULES_MAX) 137 return -EINVAL; 138 139 cm = kzalloc(sizeof(struct canid_match) + len, GFP_KERNEL); 140 if (!cm) 141 return -ENOMEM; 142 143 cm->rules_count = len / sizeof(struct can_filter); 144 145 /* 146 * We need two for() loops for copying rules into two contiguous 147 * areas in rules_raw to process all eff rules with a simple loop. 148 * NB: The configuration interface supports sff and eff rules. 149 * We do not support filters here that match for the same can_id 150 * provided in a SFF and EFF frame (e.g. 0x123 / 0x80000123). 151 * For this (unusual case) two filters have to be specified. The 152 * SFF/EFF separation is done with the CAN_EFF_FLAG in the can_id. 153 */ 154 155 /* Fill rules_raw with EFF rules first */ 156 for (i = 0; i < cm->rules_count; i++) { 157 if (conf[i].can_id & CAN_EFF_FLAG) { 158 memcpy(cm->rules_raw + cm->eff_rules_count, 159 &conf[i], 160 sizeof(struct can_filter)); 161 162 cm->eff_rules_count++; 163 } 164 } 165 166 /* append SFF frame rules */ 167 for (i = 0; i < cm->rules_count; i++) { 168 if (!(conf[i].can_id & CAN_EFF_FLAG)) { 169 memcpy(cm->rules_raw 170 + cm->eff_rules_count 171 + cm->sff_rules_count, 172 &conf[i], sizeof(struct can_filter)); 173 174 cm->sff_rules_count++; 175 176 em_canid_sff_match_add(cm, 177 conf[i].can_id, conf[i].can_mask); 178 } 179 } 180 181 m->datalen = sizeof(struct canid_match) + len; 182 m->data = (unsigned long)cm; 183 return 0; 184 } 185 186 static void em_canid_destroy(struct tcf_ematch *m) 187 { 188 struct canid_match *cm = em_canid_priv(m); 189 190 kfree(cm); 191 } 192 193 static int em_canid_dump(struct sk_buff *skb, struct tcf_ematch *m) 194 { 195 struct canid_match *cm = em_canid_priv(m); 196 197 /* 198 * When configuring this ematch 'rules_count' is set not to exceed 199 * 'rules_raw' array size 200 */ 201 if (nla_put_nohdr(skb, sizeof(struct can_filter) * cm->rules_count, 202 &cm->rules_raw) < 0) 203 return -EMSGSIZE; 204 205 return 0; 206 } 207 208 static struct tcf_ematch_ops em_canid_ops = { 209 .kind = TCF_EM_CANID, 210 .change = em_canid_change, 211 .match = em_canid_match, 212 .destroy = em_canid_destroy, 213 .dump = em_canid_dump, 214 .owner = THIS_MODULE, 215 .link = LIST_HEAD_INIT(em_canid_ops.link) 216 }; 217 218 static int __init init_em_canid(void) 219 { 220 return tcf_em_register(&em_canid_ops); 221 } 222 223 static void __exit exit_em_canid(void) 224 { 225 tcf_em_unregister(&em_canid_ops); 226 } 227 228 MODULE_DESCRIPTION("ematch classifier to match CAN IDs embedded in skb CAN frames"); 229 MODULE_LICENSE("GPL"); 230 231 module_init(init_em_canid); 232 module_exit(exit_em_canid); 233 234 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID); 235