// 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 -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->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);