OpenBSD manual page server

Creating and Destroying Sockets

A new socket may be created using socreate(). As with socket(2), arguments specify the requested domain, type, and protocol via dom, type, and proto. The socket is returned via aso on success. Warning: authorization of the socket creation operation will be performed using curproc for some protocols (such as raw sockets).

Sockets may be closed and freed using soclose(), which has similar semantics to close(2).

Connections and Addresses

The sobind() function is equivalent to the bind(2) system call, and binds the socket so to the address nam. The operation would be authorized using the credential on process p.

The soconnect() function is equivalent to the connect(2) system call, and initiates a connection on the socket so to the address nam. The operation will be authorized using the credential on curproc. Unlike the user system call, soconnect() returns immediately; the caller may tsleep(9) on so->so_timeo and wait for the SS_ISCONNECTING flag to clear or so->so_error to become non-zero. If soconnect() fails, the caller must manually clear the SS_ISCONNECTING flag.

The soshutdown() function is equivalent to the shutdown(2) system call, and causes part or all of a connection on a socket to be closed down.

Socket Options

The sogetopt() function is equivalent to the getsockopt(2) system call, and retrieves a socket option on socket so. The sosetopt() function is equivalent to the setsockopt(2) system call, and sets a socket option on socket so.

The next two arguments in both sogetopt() and sosetopt() are level and optname describing the protocol level and socket option. The last argument m is either a pointer to a prefilled mbuf or a pointer to an mbuf to retrieve data.

Socket I/O

The soreceive() function is equivalent to the recvmsg(2) system call, and attempts to receive bytes of data from the socket so, optionally blocking and awaiting data if none is ready to read. Data may be retrieved directly to kernel or user memory via the uio argument, or as an mbuf chain returned to the caller via mp0, avoiding a data copy. If mp0 is not NULL, uio must still be passed with uio_resid set to specify the maximum amount of data to be returned to the caller via an mbuf chain. The caller may optionally retrieve a socket address on a protocol with the PR_ADDR capability by providing storage via a non-NULL paddr argument. The caller may optionally retrieve up to controllen bytes of control data in mbufs via a non-NULL controlp argument. Optional flags may be passed to soreceive() via a non-NULL flagsp argument, and use the same flag name space as the recvmsg(2) system call.

When the so_upcall() function pointer is not NULL, it is called when soreceive() matches an incoming connection.

The sosend() function is equivalent to the sendmsg(2) system call, and attempts to send bytes of data via the socket so, optionally blocking if data cannot be immediately sent. Data may be sent directly from kernel or user memory via the uio argument, or as an mbuf chain via top, avoiding a data copy. Only one of the uio or top pointers may be non-NULL. An optional destination address may be specified via a non-NULL addr argument, which may result in an implicit connect if supported by the protocol. The caller may optionally send control data mbufs via a non-NULL control argument. Flags may be passed to sosend() using the flags argument, and use the same flag name space as the sendmsg(2) system call.

Kernel callers running in interrupt context, or with a mutex held, will wish to use non-blocking sockets and pass the MSG_DONTWAIT flag in order to prevent these functions from sleeping.