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SOCKOPT(9)                 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 */
                   size_t          sopt_retsize;           /* returned 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 appropriate 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 contain 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 initialised in a more
           suitable context using sockopt_init() which will not fail.

     sockopt_setint(sopt, value)
           Common case of set sockopt integer value.  The sockopt 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.

NetBSD 10.99                    January 3, 2018                   NetBSD 10.99