em_cmp.c

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/*
 * net/sched/em_cmp.c   Simple packet data comparison ematch
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * Authors: Thomas Graf <[email protected]>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/tc_ematch/tc_em_cmp.h>
#include <asm/unaligned.h>
#include <net/pkt_cls.h>

static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
{
    return unlikely(cmp->flags & TCF_EM_CMP_TRANS);
}

static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
            struct tcf_pkt_info *info)
{
    struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data;
    unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer) + cmp->off;
    u32 val = 0;

    if (!tcf_valid_offset(skb, ptr, cmp->align))
        return 0;

    switch (cmp->align) {
    case TCF_EM_ALIGN_U8:
        val = *ptr;
        break;

    case TCF_EM_ALIGN_U16:
        val = get_unaligned_be16(ptr);

        if (cmp_needs_transformation(cmp))
            val = be16_to_cpu(val);
        break;

    case TCF_EM_ALIGN_U32:
        /* Worth checking boundries? The branching seems
         * to get worse. Visit again.
         */
        val = get_unaligned_be32(ptr);

        if (cmp_needs_transformation(cmp))
            val = be32_to_cpu(val);
        break;

    default:
        return 0;
    }

    if (cmp->mask)
        val &= cmp->mask;

    switch (cmp->opnd) {
    case TCF_EM_OPND_EQ:
        return val == cmp->val;
    case TCF_EM_OPND_LT:
        return val < cmp->val;
    case TCF_EM_OPND_GT:
        return val > cmp->val;
    }

    return 0;
}

static struct tcf_ematch_ops em_cmp_ops = {
    .kind     = TCF_EM_CMP,
    .datalen  = sizeof(struct tcf_em_cmp),
    .match    = em_cmp_match,
    .owner    = THIS_MODULE,
    .link     = LIST_HEAD_INIT(em_cmp_ops.link)
};

static int __init init_em_cmp(void)
{
    return tcf_em_register(&em_cmp_ops);
}

static void __exit exit_em_cmp(void)
{
    tcf_em_unregister(&em_cmp_ops);
}

MODULE_LICENSE("GPL");

module_init(init_em_cmp);
module_exit(exit_em_cmp);

MODULE_ALIAS_TCF_EMATCH(TCF_EM_CMP);