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