/*
   * Request reply cache. This was heavily inspired by the
   * implementation in 4.3BSD/4.4BSD.
   *
   * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   */
  
  #ifndef NFSCACHE_H
  #define NFSCACHE_H
  
  #include <linux/sunrpc/svc.h>
  
  /*
   * Representation of a reply cache entry.
   *
   * Note that we use a sockaddr_in6 to hold the address instead of the more
   * typical sockaddr_storage. This is for space reasons, since sockaddr_storage
   * is much larger than a sockaddr_in6.
   */
  struct svc_cacherep {
  	struct hlist_node	c_hash;
  	struct list_head	c_lru;
  
  	unsigned char		c_state,	/* unused, inprog, done */
  				c_type,		/* status, buffer */
  				c_secure : 1;	/* req came from port < 1024 */
  	struct sockaddr_in6	c_addr;
  	__be32			c_xid;
  	u32			c_prot;
  	u32			c_proc;
  	u32			c_vers;
  	unsigned int		c_len;
  	__wsum			c_csum;
  	unsigned long		c_timestamp;
  	union {
  		struct kvec	u_vec;
  		__be32		u_status;
  	}			c_u;
  };
  
  #define c_replvec		c_u.u_vec
  #define c_replstat		c_u.u_status
  
  /* cache entry states */
  enum {
  	RC_UNUSED,
  	RC_INPROG,
  	RC_DONE
  };
  
  /* return values */
  enum {
  	RC_DROPIT,
  	RC_REPLY,
  	RC_DOIT
  };
  
  /*
   * Cache types.
   * We may want to add more types one day, e.g. for diropres and
   * attrstat replies. Using cache entries with fixed length instead
   * of buffer pointers may be more efficient.
   */
  enum {
  	RC_NOCACHE,
  	RC_REPLSTAT,
  	RC_REPLBUFF,
  };
  
  /*
   * If requests are retransmitted within this interval, they're dropped.
   */
  #define RC_DELAY		(HZ/5)
  
  /* Cache entries expire after this time period */
  #define RC_EXPIRE		(120 * HZ)
  
  /* Checksum this amount of the request */
  #define RC_CSUMLEN		(256U)
  
  int	nfsd_reply_cache_init(void);
  void	nfsd_reply_cache_shutdown(void);
  int	nfsd_cache_lookup(struct svc_rqst *);
  void	nfsd_cache_update(struct svc_rqst *, int, __be32 *);
  int	nfsd_reply_cache_stats_open(struct inode *, struct file *);
  
  #endif /* NFSCACHE_H */