net/sched/em_canid.c

   1 /*
   2  * em_canid.c  Ematch rule to match CAN frames according to their CAN IDs
   3  *
   4  *              This program is free software; you can distribute it and/or
   5  *              modify it under the terms of the GNU General Public License
   6  *              as published by the Free Software Foundation; either version
   7  *              2 of the License, or (at your option) any later version.
   8  *
   9  * Idea:       Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
  10  * Copyright:  (c) 2011 Czech Technical University in Prague
  11  *             (c) 2011 Volkswagen Group Research
  12  * Authors:    Michal Sojka <sojkam1@fel.cvut.cz>
  13  *             Pavel Pisa <pisa@cmp.felk.cvut.cz>
  14  *             Rostislav Lisovy <lisovy@gmail.cz>
  15  * Funded by:  Volkswagen Group Research
  16  */
  17
  18 #include <linux/slab.h>
  19 #include <linux/module.h>
  20 #include <linux/types.h>
  21 #include <linux/kernel.h>
  22 #include <linux/string.h>
  23 #include <linux/skbuff.h>
  24 #include <net/pkt_cls.h>
  25 #include <linux/can.h>
  26
  27 #define EM_CAN_RULES_MAX 500
  28
  29 struct canid_match {
  30         /* For each SFF CAN ID (11 bit) there is one record in this bitfield */
  31         DECLARE_BITMAP(match_sff, (1 << CAN_SFF_ID_BITS));
  32
  33         int rules_count;
  34         int sff_rules_count;
  35         int eff_rules_count;
  36
  37         /*
  38          * Raw rules copied from netlink message; Used for sending
  39          * information to userspace (when 'tc filter show' is invoked)
  40          * AND when matching EFF frames
  41          */
  42         struct can_filter rules_raw[];
  43 };
  44
  45 /**
  46  * em_canid_get_id() - Extracts Can ID out of the sk_buff structure.
  47  */
  48 static canid_t em_canid_get_id(struct sk_buff *skb)
  49 {
  50         /* CAN ID is stored within the data field */
  51         struct can_frame *cf = (struct can_frame *)skb->data;
  52
  53         return cf->can_id;
  54 }
  55
  56 static void em_canid_sff_match_add(struct canid_match *cm, u32 can_id,
  57                                         u32 can_mask)
  58 {
  59         int i;
  60
  61         /*
  62          * Limit can_mask and can_id to SFF range to
  63          * protect against write after end of array
  64          */
  65         can_mask &= CAN_SFF_MASK;
  66         can_id &= can_mask;
  67
  68         /* Single frame */
  69         if (can_mask == CAN_SFF_MASK) {
  70                 set_bit(can_id, cm->match_sff);
  71                 return;
  72         }
  73
  74         /* All frames */
  75         if (can_mask == 0) {
  76                 bitmap_fill(cm->match_sff, (1 << CAN_SFF_ID_BITS));
  77                 return;
  78         }
  79
  80         /*
  81          * Individual frame filter.
  82          * Add record (set bit to 1) for each ID that
  83          * conforms particular rule
  84          */
  85         for (i = 0; i < (1 << CAN_SFF_ID_BITS); i++) {
  86                 if ((i & can_mask) == can_id)
  87                         set_bit(i, cm->match_sff);
  88         }
  89 }
  90
  91 static inline struct canid_match *em_canid_priv(struct tcf_ematch *m)
  92 {
  93         return (struct canid_match *)m->data;
  94 }
  95
  96 static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m,
  97                          struct tcf_pkt_info *info)
  98 {
  99         struct canid_match *cm = em_canid_priv(m);
 100         canid_t can_id;
 101         int match = 0;
 102         int i;
 103         const struct can_filter *lp;
 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_LICENSE("GPL");
 229
 230 module_init(init_em_canid);
 231 module_exit(exit_em_canid);
 232
 233 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID);