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 */ 44 static canid_t em_canid_get_id(struct sk_buff *skb) 45 { 46 /* CAN ID is stored within the data field */ 47 struct can_frame *cf = (struct can_frame *)skb->data; 48 49 return cf->can_id; 50 } 51 52 static void em_canid_sff_match_add(struct canid_match *cm, u32 can_id, 53 u32 can_mask) 54 { 55 int i; 56 57 /* 58 * Limit can_mask and can_id to SFF range to 59 * protect against write after end of array 60 */ 61 can_mask &= CAN_SFF_MASK; 62 can_id &= can_mask; 63 64 /* Single frame */ 65 if (can_mask == CAN_SFF_MASK) { 66 set_bit(can_id, cm->match_sff); 67 return; 68 } 69 70 /* All frames */ 71 if (can_mask == 0) { 72 bitmap_fill(cm->match_sff, (1 << CAN_SFF_ID_BITS)); 73 return; 74 } 75 76 /* 77 * Individual frame filter. 78 * Add record (set bit to 1) for each ID that 79 * conforms particular rule 80 */ 81 for (i = 0; i < (1 << CAN_SFF_ID_BITS); i++) { 82 if ((i & can_mask) == can_id) 83 set_bit(i, cm->match_sff); 84 } 85 } 86 87 static inline struct canid_match *em_canid_priv(struct tcf_ematch *m) 88 { 89 return (struct canid_match *)m->data; 90 } 91 92 static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m, 93 struct tcf_pkt_info *info) 94 { 95 struct canid_match *cm = em_canid_priv(m); 96 canid_t can_id; 97 int match = 0; 98 int i; 99 const struct can_filter *lp; 100 101 can_id = em_canid_get_id(skb); 102 103 if (can_id & CAN_EFF_FLAG) { 104 for (i = 0, lp = cm->rules_raw; 105 i < cm->eff_rules_count; i++, lp++) { 106 if (!(((lp->can_id ^ can_id) & lp->can_mask))) { 107 match = 1; 108 break; 109 } 110 } 111 } else { /* SFF */ 112 can_id &= CAN_SFF_MASK; 113 match = (test_bit(can_id, cm->match_sff) ? 1 : 0); 114 } 115 116 return match; 117 } 118 119 static int em_canid_change(struct net *net, void *data, int len, 120 struct tcf_ematch *m) 121 { 122 struct can_filter *conf = data; /* Array with rules */ 123 struct canid_match *cm; 124 int i; 125 126 if (!len) 127 return -EINVAL; 128 129 if (len % sizeof(struct can_filter)) 130 return -EINVAL; 131 132 if (len > sizeof(struct can_filter) * EM_CAN_RULES_MAX) 133 return -EINVAL; 134 135 cm = kzalloc(sizeof(struct canid_match) + len, GFP_KERNEL); 136 if (!cm) 137 return -ENOMEM; 138 139 cm->rules_count = len / sizeof(struct can_filter); 140 141 /* 142 * We need two for() loops for copying rules into two contiguous 143 * areas in rules_raw to process all eff rules with a simple loop. 144 * NB: The configuration interface supports sff and eff rules. 145 * We do not support filters here that match for the same can_id 146 * provided in a SFF and EFF frame (e.g. 0x123 / 0x80000123). 147 * For this (unusual case) two filters have to be specified. The 148 * SFF/EFF separation is done with the CAN_EFF_FLAG in the can_id. 149 */ 150 151 /* Fill rules_raw with EFF rules first */ 152 for (i = 0; i < cm->rules_count; i++) { 153 if (conf[i].can_id & CAN_EFF_FLAG) { 154 memcpy(cm->rules_raw + cm->eff_rules_count, 155 &conf[i], 156 sizeof(struct can_filter)); 157 158 cm->eff_rules_count++; 159 } 160 } 161 162 /* append SFF frame rules */ 163 for (i = 0; i < cm->rules_count; i++) { 164 if (!(conf[i].can_id & CAN_EFF_FLAG)) { 165 memcpy(cm->rules_raw 166 + cm->eff_rules_count 167 + cm->sff_rules_count, 168 &conf[i], sizeof(struct can_filter)); 169 170 cm->sff_rules_count++; 171 172 em_canid_sff_match_add(cm, 173 conf[i].can_id, conf[i].can_mask); 174 } 175 } 176 177 m->datalen = sizeof(struct canid_match) + len; 178 m->data = (unsigned long)cm; 179 return 0; 180 } 181 182 static void em_canid_destroy(struct tcf_ematch *m) 183 { 184 struct canid_match *cm = em_canid_priv(m); 185 186 kfree(cm); 187 } 188 189 static int em_canid_dump(struct sk_buff *skb, struct tcf_ematch *m) 190 { 191 struct canid_match *cm = em_canid_priv(m); 192 193 /* 194 * When configuring this ematch 'rules_count' is set not to exceed 195 * 'rules_raw' array size 196 */ 197 if (nla_put_nohdr(skb, sizeof(struct can_filter) * cm->rules_count, 198 &cm->rules_raw) < 0) 199 return -EMSGSIZE; 200 201 return 0; 202 } 203 204 static struct tcf_ematch_ops em_canid_ops = { 205 .kind = TCF_EM_CANID, 206 .change = em_canid_change, 207 .match = em_canid_match, 208 .destroy = em_canid_destroy, 209 .dump = em_canid_dump, 210 .owner = THIS_MODULE, 211 .link = LIST_HEAD_INIT(em_canid_ops.link) 212 }; 213 214 static int __init init_em_canid(void) 215 { 216 return tcf_em_register(&em_canid_ops); 217 } 218 219 static void __exit exit_em_canid(void) 220 { 221 tcf_em_unregister(&em_canid_ops); 222 } 223 224 MODULE_LICENSE("GPL"); 225 226 module_init(init_em_canid); 227 module_exit(exit_em_canid); 228 229 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID); 230