1 files changed, 93 insertions, 0 deletions
diff --git a/src/syscall/sockcmsg_unix.go b/src/syscall/sockcmsg_unix.go
new file mode 100644
index 0000000..99913b9
--- /dev/null
+++ b/src/syscall/sockcmsg_unix.go
@@ -0,0 +1,93 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+// Socket control messages
+
+package syscall
+
+import (
+	"unsafe"
+)
+
+// CmsgLen returns the value to store in the Len field of the Cmsghdr
+// structure, taking into account any necessary alignment.
+func CmsgLen(datalen int) int {
+	return cmsgAlignOf(SizeofCmsghdr) + datalen
+}
+
+// CmsgSpace returns the number of bytes an ancillary element with
+// payload of the passed data length occupies.
+func CmsgSpace(datalen int) int {
+	return cmsgAlignOf(SizeofCmsghdr) + cmsgAlignOf(datalen)
+}
+
+func (h *Cmsghdr) data(offset uintptr) unsafe.Pointer {
+	return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)) + offset)
+}
+
+// SocketControlMessage represents a socket control message.
+type SocketControlMessage struct {
+	Header Cmsghdr
+	Data   []byte
+}
+
+// ParseSocketControlMessage parses b as an array of socket control
+// messages.
+func ParseSocketControlMessage(b []byte) ([]SocketControlMessage, error) {
+	var msgs []SocketControlMessage
+	i := 0
+	for i+CmsgLen(0) <= len(b) {
+		h, dbuf, err := socketControlMessageHeaderAndData(b[i:])
+		if err != nil {
+			return nil, err
+		}
+		m := SocketControlMessage{Header: *h, Data: dbuf}
+		msgs = append(msgs, m)
+		i += cmsgAlignOf(int(h.Len))
+	}
+	return msgs, nil
+}
+
+func socketControlMessageHeaderAndData(b []byte) (*Cmsghdr, []byte, error) {
+	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
+	if h.Len < SizeofCmsghdr || uint64(h.Len) > uint64(len(b)) {
+		return nil, nil, EINVAL
+	}
+	return h, b[cmsgAlignOf(SizeofCmsghdr):h.Len], nil
+}
+
+// UnixRights encodes a set of open file descriptors into a socket
+// control message for sending to another process.
+func UnixRights(fds ...int) []byte {
+	datalen := len(fds) * 4
+	b := make([]byte, CmsgSpace(datalen))
+	h := (*Cmsghdr)(unsafe.Pointer(&b[0]))
+	h.Level = SOL_SOCKET
+	h.Type = SCM_RIGHTS
+	h.SetLen(CmsgLen(datalen))
+	for i, fd := range fds {
+		*(*int32)(h.data(4 * uintptr(i))) = int32(fd)
+	}
+	return b
+}
+
+// ParseUnixRights decodes a socket control message that contains an
+// integer array of open file descriptors from another process.
+func ParseUnixRights(m *SocketControlMessage) ([]int, error) {
+	if m.Header.Level != SOL_SOCKET {
+		return nil, EINVAL
+	}
+	if m.Header.Type != SCM_RIGHTS {
+		return nil, EINVAL
+	}
+	fds := make([]int, len(m.Data)>>2)
+	for i, j := 0, 0; i < len(m.Data); i += 4 {
+		fds[j] = int(*(*int32)(unsafe.Pointer(&m.Data[i])))
+		j++
+	}
+	return fds, nil
+}