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 <asm/unaligned.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 = get_unaligned_be16(ptr);
  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                  */
  51                 val = get_unaligned_be32(ptr);
  52
  53                 if (cmp_needs_transformation(cmp))
  54                         val = be32_to_cpu(val);
  55                 break;
  56
  57         default:
  58                 return 0;
  59         }
  60
  61         if (cmp->mask)
  62                 val &= cmp->mask;
  63
  64         switch (cmp->opnd) {
  65         case TCF_EM_OPND_EQ:
  66                 return val == cmp->val;
  67         case TCF_EM_OPND_LT:
  68                 return val < cmp->val;
  69         case TCF_EM_OPND_GT:
  70                 return val > cmp->val;
  71         }
  72
  73         return 0;
  74 }
  75
  76 static struct tcf_ematch_ops em_cmp_ops = {
  77         .kind     = TCF_EM_CMP,
  78         .datalen  = sizeof(struct tcf_em_cmp),
  79         .match    = em_cmp_match,
  80         .owner    = THIS_MODULE,
  81         .link     = LIST_HEAD_INIT(em_cmp_ops.link)
  82 };
  83
  84 static int __init init_em_cmp(void)
  85 {
  86         return tcf_em_register(&em_cmp_ops);
  87 }
  88
  89 static void __exit exit_em_cmp(void)
  90 {
  91         tcf_em_unregister(&em_cmp_ops);
  92 }
  93
  94 MODULE_LICENSE("GPL");
  95
  96 module_init(init_em_cmp);
  97 module_exit(exit_em_cmp);
  98
  99 MODULE_ALIAS_TCF_EMATCH(TCF_EM_CMP);