linux/net/sched/em_cmp.c
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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/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
  20static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
  21{
  22        return unlikely(cmp->flags & TCF_EM_CMP_TRANS);
  23}
  24
  25static 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
  76static 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
  84static int __init init_em_cmp(void)
  85{
  86        return tcf_em_register(&em_cmp_ops);
  87}
  88
  89static void __exit exit_em_cmp(void)
  90{
  91        tcf_em_unregister(&em_cmp_ops);
  92}
  93
  94MODULE_LICENSE("GPL");
  95
  96module_init(init_em_cmp);
  97module_exit(exit_em_cmp);
  98
  99MODULE_ALIAS_TCF_EMATCH(TCF_EM_CMP);
 100
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