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