October 28, 2008 SOCKOPT 9

### NAME

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

### SYNOPSIS

```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.

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 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

This section describes places within the NetBSD source tree where code implementing socket options can be found. All pathnames are relative to ```/usr/src`.

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_alloc(9)

### HISTORY

The socket options KPI was inspired by a similar KPI in FreeBSD and first appeared in NetBSD5.0.