Creating a socket in Golang

golang-rawsocket-syscall.go

// This unimplemnted function is found in the syscall/syscall_linx_386.go file and is referenced by the socket function below.
// It is implemented in the syscall/asm_linux_s390x.s file
func rawsocketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err Errno)

golang-socket-syscall.go

// The bind method mirrors the Unix API for bind calls. A call to rawsocketcall is made (see methods above)
func bind(s int, addr unsafe.Pointer, addrlen _Socklen) (err error) {
	_, e := socketcall(_BIND, uintptr(s), uintptr(addr), uintptr(addrlen), 0, 0, 0)
	if e != 0 {
		err = e
	}
	return
}

// The socket method mirrors the Unix API for Socket calls. A call to rawsocketcall is made (see method above and below)
func socket(domain int, typ int, proto int) (fd int, err error) {
	fd, e := rawsocketcall(_SOCKET, uintptr(domain), uintptr(typ), uintptr(proto), 0, 0, 0)
	if e != 0 {
		err = e
	}
	return
}

rawsocketcall-impl.s

// func rawsocketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err int)
// Kernel interface gets call sub-number and pointer to a0.
// This method is found in the syscall/asm_linux_s390x.s file
TEXT ·rawsocketcall(SB),NOSPLIT,$0-72
	MOVD	$SYS_SOCKETCALL, R1	// syscall entry
	MOVD	call+0(FP), R2		// socket call number
	MOVD	$a0+8(FP), R3		// pointer to call arguments
	MOVD	$0, R4
	MOVD	$0, R5
	MOVD	$0, R6
	MOVD	$0, R7
	SYSCALL
	MOVD	$0xfffffffffffff001, R8
	CMPUBLT	R2, R8, oksock1
	MOVD	$-1, n+56(FP)
	NEG	R2, R2
	MOVD	R2, err+64(FP)
	RET
oksock1:
	MOVD	R2, n+56(FP)
	MOVD	$0, err+64(FP)
	RET