net/sched/em_cmp.c

   1 /*
   2  * net/sched/em_cmp.c   Simple packet data comparison ematch
   3  *
   4  *              This program is free software; you can redistribute 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  * Authors:     Thomas Graf <tgraf@suug.ch>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/tc_ematch/tc_em_cmp.h>
  17 #include <net/pkt_cls.h>
  18
  19 static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
  20 {
  21         return unlikely(cmp->flags & TCF_EM_CMP_TRANS);
  22 }
  23
  24 static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
  25                         struct tcf_pkt_info *info)
  26 {
  27         struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data;
  28         unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer) + cmp->off;
  29         u32 val = 0;
  30
  31         if (!tcf_valid_offset(skb, ptr, cmp->align))
  32                 return 0;
  33
  34         switch (cmp->align) {
  35                 case TCF_EM_ALIGN_U8:
  36                         val = *ptr;
  37                         break;
  38
  39                 case TCF_EM_ALIGN_U16:
  40                         val = *ptr << 8;
  41                         val |= *(ptr+1);
  42
  43                         if (cmp_needs_transformation(cmp))
  44                                 val = be16_to_cpu(val);
  45                         break;
  46
  47                 case TCF_EM_ALIGN_U32:
  48                         /* Worth checking boundries? The branching seems
  49                          * to get worse. Visit again. */
  50                         val = *ptr << 24;
  51                         val |= *(ptr+1) << 16;
  52                         val |= *(ptr+2) << 8;
  53                         val |= *(ptr+3);
  54
  55                         if (cmp_needs_transformation(cmp))
  56                                 val = be32_to_cpu(val);
  57                         break;
  58
  59                 default:
  60                         return 0;
  61         }
  62
  63         if (cmp->mask)
  64                 val &= cmp->mask;
  65
  66         switch (cmp->opnd) {
  67                 case TCF_EM_OPND_EQ:
  68                         return val == cmp->val;
  69                 case TCF_EM_OPND_LT:
  70                         return val < cmp->val;
  71                 case TCF_EM_OPND_GT:
  72                         return val > cmp->val;
  73         }
  74
  75         return 0;
  76 }
  77
  78 static struct tcf_ematch_ops em_cmp_ops = {
  79         .kind     = TCF_EM_CMP,
  80         .datalen  = sizeof(struct tcf_em_cmp),
  81         .match    = em_cmp_match,
  82         .owner    = THIS_MODULE,
  83         .link     = LIST_HEAD_INIT(em_cmp_ops.link)
  84 };
  85
  86 static int __init init_em_cmp(void)
  87 {
  88         return tcf_em_register(&em_cmp_ops);
  89 }
  90
  91 static void __exit exit_em_cmp(void)
  92 {
  93         tcf_em_unregister(&em_cmp_ops);
  94 }
  95
  96 MODULE_LICENSE("GPL");
  97
  98 module_init(init_em_cmp);
  99 module_exit(exit_em_cmp);
 100
 101 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CMP);