// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * net/sched/em_cmp.c	Simple packet data comparison ematch
   *

   * Authors:	Thomas Graf <tgraf@suug.ch>
   */

  #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);