em_nbyte.c

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/*
 * net/sched/em_nbyte.c N-Byte 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/gfp.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/tc_ematch/tc_em_nbyte.h>
#include <net/pkt_cls.h>

struct nbyte_data {
    struct tcf_em_nbyte hdr;
    char            pattern[0];
};

static int em_nbyte_change(struct tcf_proto *tp, void *data, int data_len,
               struct tcf_ematch *em)
{
    struct tcf_em_nbyte *nbyte = data;

    if (data_len < sizeof(*nbyte) ||
        data_len < (sizeof(*nbyte) + nbyte->len))
        return -EINVAL;

    em->datalen = sizeof(*nbyte) + nbyte->len;
    em->data = (unsigned long)kmemdup(data, em->datalen, GFP_KERNEL);
    if (em->data == 0UL)
        return -ENOBUFS;

    return 0;
}

static int em_nbyte_match(struct sk_buff *skb, struct tcf_ematch *em,
              struct tcf_pkt_info *info)
{
    struct nbyte_data *nbyte = (struct nbyte_data *) em->data;
    unsigned char *ptr = tcf_get_base_ptr(skb, nbyte->hdr.layer);

    ptr += nbyte->hdr.off;

    if (!tcf_valid_offset(skb, ptr, nbyte->hdr.len))
        return 0;

    return !memcmp(ptr + nbyte->hdr.off, nbyte->pattern, nbyte->hdr.len);
}

static struct tcf_ematch_ops em_nbyte_ops = {
    .kind     = TCF_EM_NBYTE,
    .change   = em_nbyte_change,
    .match    = em_nbyte_match,
    .owner    = THIS_MODULE,
    .link     = LIST_HEAD_INIT(em_nbyte_ops.link)
};

static int __init init_em_nbyte(void)
{
    return tcf_em_register(&em_nbyte_ops);
}

static void __exit exit_em_nbyte(void)
{
    tcf_em_unregister(&em_nbyte_ops);
}

MODULE_LICENSE("GPL");

module_init(init_em_nbyte);
module_exit(exit_em_nbyte);

MODULE_ALIAS_TCF_EMATCH(TCF_EM_NBYTE);