// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/em_nbyte.c N-Byte ematch
 *
 * Authors:     Thomas Graf <tgraf@suug.ch>
 */

#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[];
};

static int em_nbyte_change(struct net *net, 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 -ENOMEM;

        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);

        if (!ptr)
                return 0;
        ptr += nbyte->hdr.off;

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

        return !memcmp(ptr, 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_DESCRIPTION("ematch classifier for arbitrary skb multi-bytes");
MODULE_LICENSE("GPL");

module_init(init_em_nbyte);
module_exit(exit_em_nbyte);

MODULE_ALIAS_TCF_EMATCH(TCF_EM_NBYTE);