net/sched/em_canid.c

   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);