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NetBSD 6.1.5 - man page for sockopt_init (netbsd section 9)

SOCKOPT(9)			  BSD Kernel Developer's Manual 		       SOCKOPT(9)

NAME
     sockopt_init, sockopt_destroy, sockopt_get, sockopt_getint sockopt_set, sockopt_setint, --
     socket options handling

SYNOPSIS
     #include <sys/socketvar.h>

     void
     sockopt_init(struct sockopt *sopt, int level, int name, size_t size);

     void
     sockopt_destroy(struct sockopt *sopt);

     int
     sockopt_get(struct sockopt *sopt, void *value, size_t size);

     int
     sockopt_getint(struct sockopt *sopt, int *value);

     int
     sockopt_set(struct sockopt *sopt, const void *value, size_t size);

     int
     sockopt_setint(struct sockopt *sopt, int value);

DESCRIPTION
     The sockopt structure is used to pass a socket option and associated value:

	   struct sockopt {
		   int		   sopt_level;		   /* option level */
		   int		   sopt_name;		   /* option name */
		   size_t	   sopt_size;		   /* data length */
		   void *	   sopt_data;		   /* data pointer */
		   uint8_t	   sopt_buf[sizeof(int)];  /* internal storage */
	   };

     The internal storage is used for the common case of values up to integer size so that memory
     allocation is not required and sopt_data will point to this in that case.

     Rather than provide accessor functions, the sockopt structure is public and the contents are
     expected to be internally consistent, but the normal practice would be to use the appropri-
     ate methods for storage and retrieval of values where a known datatype is expected, as the
     size will be verified.

     Note: a sockopt structure may only be used for a single level/name/size combination.  If the
     structure is to be re-used, it must be destroyed and re-initialized with the new values.

OPTIONS
     options DIAGNOSTIC
	   Kernels compiled with the DIAGNOSTIC option will perform basic sanity checks on socket
	   options operations.

FUNCTIONS
     sockopt_init(sopt, level, name, size)
	   Initialise sockopt storage.	If size is given, sockopt_init() will arrange for
	   sopt_data to point to a buffer of size bytes for the sockopt value.	Where memory
	   needs to be allocated to satisfy this, sockopt_init() may sleep.

     sockopt_destroy(sopt)
	   Destroy sockopt storage, releasing any allocated memory.

     sockopt_get(sopt, value, size)
	   Copy out sockopt value.  Will return EINVAL if an incorrect data size is given.

     sockopt_getint(sopt, value)
	   Common case of get sockopt integer value.  Will return EINVAL if sockopt does not con-
	   tain an integer sized value.

     sockopt_set(sopt, value, size)
	   Copy in sockopt value.  The sockopt structure must contain a data field of size bytes
	   or be previously unset, in which case a data buffer may be allocated using
	   kmem_alloc(9) with the KM_NOSLEEP flag which may cause sockopt_set() to return ENOMEM.

	   Note: If you need to use sockopt_set() in a context where memory allocation may be
	   required and you do not wish to contemplate failure, the sockopt structure can be ini-
	   tialised in a more suitable context using sockopt_init() which will not fail.

     sockopt_setint(sopt, value)
	   Common case of set sockopt integer value.  The sockpt structure must contain an int
	   sized data field or be previously unset, in which case the data pointer will be set to
	   the internal storage.

CODE REFERENCES
     The function prototypes and sockopt structure are defined in the sys/sys/socketvar.h header
     file, and the socket options implementation is in sys/kern/uipc_socket.c.

SEE ALSO
     errno(2), kmem(9)

HISTORY
     The socket options KPI was inspired by a similar KPI in FreeBSD and first appeared in
     NetBSD 5.0.

BSD					September 4, 2009				      BSD


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