sockopt(9)
- NetBSD Manual Pages
SOCKOPT(9) NetBSD 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 san-
ity 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 fail-
ure, 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 9.2 January 3, 2018 NetBSD 9.2
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