// 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);