9.85 getsockopt/setsockopt ¶

#define SOL_SOCKET 1

#define SO_ACCEPTCONN 1
#define SO_ERROR      5
#define SO_SNDBUF     13
#define SO_TYPE       16
#define SO_PEERCRED   18
#define SO_PASSCRED   20

int getsockopt(int fd, int level, int name, void *val, socklen_t *len);
int setsockopt(int fd, int level, int name, void *val, socklen_t len);

This syscall gets or sets the option passed on name for the socket level passed on level, and writes or fetches data from val with the length passed on len.

Right now, SOL_SOCKET is the only supported socket level.

name can be one of:

SO_ACCEPTCONN

val will point to an uint32_t. 1 will be written there if the passed socket is listening, and 0 if it is not/cannot listen due to protocol. getsockopt only.

SO_ERROR

val will point to an uint32_t. The value will be written with the present socket error if any, or 0 if none are present. getsockopt only.

SO_SNDBUF

val will point to an uint32_t. If getting the value, the current send-buffer size will be returned, else, it setting it, the passed size will be used for the same buffer.

SO_TYPE

val will point to an uint32_t. The type of socket will be returned in that variable in the same format as see socket. getsockopt only.

SO_PEERCRED

val points to a struct of three uint32_t values, the pid, uid, and gid of the peer.

SO_PASSCRED

val is a 32 bit integer value that is zero or one. One when set or retrieved means that the socket will receive ancillary SCM_CREDENTIALS data when receiving messages, if not enabled, no credentials data will be received even if explicitly sent.

The syscall returns 0 on success or -1 on failure, with the errno:

EBADF

fd was not open, or is not a socket.

EACCES

val did not point to valid memory.

EINVAL

The passed name or level were not valid.