/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef __6LOWPAN_NHC_H
  #define __6LOWPAN_NHC_H
  
  #include <linux/skbuff.h>
  #include <linux/rbtree.h>
  #include <linux/module.h>
  
  #include <net/6lowpan.h>
  #include <net/ipv6.h>

  /**
   * LOWPAN_NHC - helper macro to generate nh id fields and lowpan_nhc struct
   *
   * @__nhc: variable name of the lowpan_nhc struct.
   * @_name: const char * of common header compression name.
   * @_nexthdr: ipv6 nexthdr field for the header compression.
   * @_nexthdrlen: ipv6 nexthdr len for the reserved space.
   * @_idsetup: callback to setup id and mask values.
   * @_idlen: len for the next header id and mask, should be always the same.
   * @_uncompress: callback for uncompression call.
   * @_compress: callback for compression call.
   */
  #define LOWPAN_NHC(__nhc, _name, _nexthdr,	\
  		   _hdrlen, _idsetup, _idlen,	\
  		   _uncompress, _compress)	\
  static u8 __nhc##_val[_idlen];			\
  static u8 __nhc##_mask[_idlen];			\
  static struct lowpan_nhc __nhc = {		\
  	.name		= _name,		\
  	.nexthdr	= _nexthdr,		\
  	.nexthdrlen	= _hdrlen,		\
  	.id		= __nhc##_val,		\
  	.idmask		= __nhc##_mask,		\
  	.idlen		= _idlen,		\
  	.idsetup	= _idsetup,		\
  	.uncompress	= _uncompress,		\
  	.compress	= _compress,		\
  }
  
  #define module_lowpan_nhc(__nhc)		\
  static int __init __nhc##_init(void)		\
  {						\
  	return lowpan_nhc_add(&(__nhc));	\
  }						\
  module_init(__nhc##_init);			\
  static void __exit __nhc##_exit(void)		\
  {						\
  	lowpan_nhc_del(&(__nhc));		\
  }						\
  module_exit(__nhc##_exit);
  
  /**
   * struct lowpan_nhc - hold 6lowpan next hdr compression ifnformation
   *
   * @node: holder for the rbtree.
   * @name: name of the specific next header compression
   * @nexthdr: next header value of the protocol which should be compressed.
   * @nexthdrlen: ipv6 nexthdr len for the reserved space.
   * @id: array for nhc id. Note this need to be in network byteorder.
   * @mask: array for nhc id mask. Note this need to be in network byteorder.
   * @len: the length of the next header id and mask.
   * @setup: callback to setup fill the next header id value and mask.
   * @compress: callback to do the header compression.
   * @uncompress: callback to do the header uncompression.
   */
  struct lowpan_nhc {
  	struct rb_node	node;
  	const char	*name;
  	const u8	nexthdr;
  	const size_t	nexthdrlen;
  	u8		*id;
  	u8		*idmask;
  	const size_t	idlen;
  
  	void		(*idsetup)(struct lowpan_nhc *nhc);
  	int		(*uncompress)(struct sk_buff *skb, size_t needed);
  	int		(*compress)(struct sk_buff *skb, u8 **hc_ptr);
  };
  
  /**
   * lowpan_nhc_by_nexthdr - return the 6lowpan nhc by ipv6 nexthdr.
   *
   * @nexthdr: ipv6 nexthdr value.
   */
  struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr);
  
  /**
   * lowpan_nhc_check_compression - checks if we support compression format. If

   *	we support the nhc by nexthdr field, the function will return 0. If we
   *	don't support the nhc by nexthdr this function will return -ENOENT.

   *
   * @skb: skb of 6LoWPAN header to read nhc and replace header.
   * @hdr: ipv6hdr to check the nexthdr value
   * @hc_ptr: pointer for 6LoWPAN header which should increment at the end of
   *	    replaced header.

   */
  int lowpan_nhc_check_compression(struct sk_buff *skb,

  				 const struct ipv6hdr *hdr, u8 **hc_ptr);

  
  /**
   * lowpan_nhc_do_compression - calling compress callback for nhc
   *
   * @skb: skb of 6LoWPAN header to read nhc and replace header.
   * @hdr: ipv6hdr to set the nexthdr value
   * @hc_ptr: pointer for 6LoWPAN header which should increment at the end of
   *	    replaced header.
   */
  int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
  			      u8 **hc_ptr);
  
  /**
   * lowpan_nhc_do_uncompression - calling uncompress callback for nhc
   *
   * @nhc: 6LoWPAN nhc context, get by lowpan_nhc_by_ functions.
   * @skb: skb of 6LoWPAN header, skb->data should be pointed to nhc id value.
   * @dev: netdevice for print logging information.
   * @hdr: ipv6hdr for setting nexthdr value.
   */

  int lowpan_nhc_do_uncompression(struct sk_buff *skb,
  				const struct net_device *dev,

  				struct ipv6hdr *hdr);
  
  /**
   * lowpan_nhc_add - register a next header compression to framework
   *
   * @nhc: nhc which should be add.
   */
  int lowpan_nhc_add(struct lowpan_nhc *nhc);
  
  /**
   * lowpan_nhc_del - delete a next header compression from framework
   *
   * @nhc: nhc which should be delete.
   */
  void lowpan_nhc_del(struct lowpan_nhc *nhc);
  
  /**
   * lowpan_nhc_init - adding all default nhcs
   */
  void lowpan_nhc_init(void);
  
  #endif /* __6LOWPAN_NHC_H */