/* SPDX-License-Identifier: GPL-2.0 */
  /*
   * Multipath TCP
   *
   * Copyright (c) 2017 - 2019, Intel Corporation.
   */
  
  #ifndef __NET_MPTCP_H
  #define __NET_MPTCP_H

  #include <linux/skbuff.h>

  #include <linux/tcp.h>

  #include <linux/types.h>

  struct seq_file;

  /* MPTCP sk_buff extension data */
  struct mptcp_ext {

  	union {
  		u64	data_ack;
  		u32	data_ack32;
  	};

  	u64		data_seq;
  	u32		subflow_seq;
  	u16		data_len;
  	u8		use_map:1,
  			dsn64:1,
  			data_fin:1,
  			use_ack:1,
  			ack64:1,

  			mpc_map:1,
  			__unused:2;

  	/* one byte hole */
  };

  struct mptcp_out_options {
  #if IS_ENABLED(CONFIG_MPTCP)
  	u16 suboptions;
  	u64 sndr_key;
  	u64 rcvr_key;

  	union {
  		struct in_addr addr;
  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
  		struct in6_addr addr6;
  #endif
  	};
  	u8 addr_id;
  	u64 ahmac;
  	u8 rm_id;

  	u8 join_id;
  	u8 backup;
  	u32 nonce;
  	u64 thmac;

  	u32 token;
  	u8 hmac[20];

  	struct mptcp_ext ext_copy;

  #endif
  };

  #ifdef CONFIG_MPTCP

  extern struct request_sock_ops mptcp_subflow_request_sock_ops;

  void mptcp_init(void);

  static inline bool sk_is_mptcp(const struct sock *sk)
  {
  	return tcp_sk(sk)->is_mptcp;
  }
  
  static inline bool rsk_is_mptcp(const struct request_sock *req)
  {
  	return tcp_rsk(req)->is_mptcp;
  }

  static inline bool rsk_drop_req(const struct request_sock *req)
  {
  	return tcp_rsk(req)->is_mptcp && tcp_rsk(req)->drop_req;
  }

  void mptcp_space(const struct sock *ssk, int *space, int *full_space);

  bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
  		       unsigned int *size, struct mptcp_out_options *opts);

  bool mptcp_synack_options(const struct request_sock *req, unsigned int *size,
  			  struct mptcp_out_options *opts);
  bool mptcp_established_options(struct sock *sk, struct sk_buff *skb,
  			       unsigned int *size, unsigned int remaining,
  			       struct mptcp_out_options *opts);

  void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb);

  void mptcp_write_options(__be32 *ptr, struct mptcp_out_options *opts);

  /* move the skb extension owership, with the assumption that 'to' is
   * newly allocated
   */
  static inline void mptcp_skb_ext_move(struct sk_buff *to,
  				      struct sk_buff *from)
  {
  	if (!skb_ext_exist(from, SKB_EXT_MPTCP))
  		return;
  
  	if (WARN_ON_ONCE(to->active_extensions))
  		skb_ext_put(to);
  
  	to->active_extensions = from->active_extensions;
  	to->extensions = from->extensions;
  	from->active_extensions = 0;
  }
  
  static inline bool mptcp_ext_matches(const struct mptcp_ext *to_ext,
  				     const struct mptcp_ext *from_ext)
  {
  	/* MPTCP always clears the ext when adding it to the skb, so
  	 * holes do not bother us here
  	 */
  	return !from_ext ||
  	       (to_ext && from_ext &&
  	        !memcmp(from_ext, to_ext, sizeof(struct mptcp_ext)));
  }
  
  /* check if skbs can be collapsed.
   * MPTCP collapse is allowed if neither @to or @from carry an mptcp data
   * mapping, or if the extension of @to is the same as @from.
   * Collapsing is not possible if @to lacks an extension, but @from carries one.
   */
  static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
  					  const struct sk_buff *from)
  {
  	return mptcp_ext_matches(skb_ext_find(to, SKB_EXT_MPTCP),
  				 skb_ext_find(from, SKB_EXT_MPTCP));
  }

  void mptcp_seq_show(struct seq_file *seq);

  int mptcp_subflow_init_cookie_req(struct request_sock *req,
  				  const struct sock *sk_listener,
  				  struct sk_buff *skb);

  #else

  static inline void mptcp_init(void)
  {
  }

  static inline bool sk_is_mptcp(const struct sock *sk)
  {
  	return false;
  }
  
  static inline bool rsk_is_mptcp(const struct request_sock *req)
  {
  	return false;
  }

  static inline bool rsk_drop_req(const struct request_sock *req)
  {
  	return false;
  }

  static inline void mptcp_parse_option(const struct sk_buff *skb,
  				      const unsigned char *ptr, int opsize,

  				      struct tcp_options_received *opt_rx)
  {
  }

  static inline bool mptcp_syn_options(struct sock *sk, const struct sk_buff *skb,
  				     unsigned int *size,

  				     struct mptcp_out_options *opts)
  {
  	return false;
  }

  static inline bool mptcp_synack_options(const struct request_sock *req,
  					unsigned int *size,
  					struct mptcp_out_options *opts)
  {
  	return false;
  }
  
  static inline bool mptcp_established_options(struct sock *sk,
  					     struct sk_buff *skb,
  					     unsigned int *size,
  					     unsigned int remaining,
  					     struct mptcp_out_options *opts)
  {
  	return false;
  }

  static inline void mptcp_incoming_options(struct sock *sk,

  					  struct sk_buff *skb)

  {
  }

  static inline void mptcp_skb_ext_move(struct sk_buff *to,
  				      const struct sk_buff *from)
  {
  }
  
  static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
  					  const struct sk_buff *from)
  {
  	return true;
  }

  static inline void mptcp_space(const struct sock *ssk, int *s, int *fs) { }

  static inline void mptcp_seq_show(struct seq_file *seq) { }

  
  static inline int mptcp_subflow_init_cookie_req(struct request_sock *req,
  						const struct sock *sk_listener,
  						struct sk_buff *skb)
  {
  	return 0; /* TCP fallback */
  }

  #endif /* CONFIG_MPTCP */

  
  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
  int mptcpv6_init(void);

  void mptcpv6_handle_mapped(struct sock *sk, bool mapped);

  #elif IS_ENABLED(CONFIG_IPV6)

  static inline int mptcpv6_init(void) { return 0; }
  static inline void mptcpv6_handle_mapped(struct sock *sk, bool mapped) { }

  #endif

  #endif /* __NET_MPTCP_H */