vendor: add golang.org/x/sys/unix@9a7256cb28ed514b4e1e5f68959914c4c28a92e0

It turns out that the standard "syscall" library is not recommended for
new programs. runC will need to eventually move to this, but for now
include it in vendor so we can use it for new features.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

vendor/golang.org/x/sys/unix/sockcmsg_unix.go

@@ -0,0 +1,103 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+// Socket control messages
+
+package unix
+
+import "unsafe"
+
+// Round the length of a raw sockaddr up to align it properly.
+func cmsgAlignOf(salen int) int {
+	salign := sizeofPtr
+	// NOTE: It seems like 64-bit Darwin and DragonFly BSD kernels
+	// still require 32-bit aligned access to network subsystem.
+	if darwin64Bit || dragonfly64Bit {
+		salign = 4
+	}
+	return (salen + salign - 1) & ^(salign - 1)
+}
+
+// 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 cmsgData(h *Cmsghdr) unsafe.Pointer {
+	return unsafe.Pointer(uintptr(unsafe.Pointer(h)) + uintptr(cmsgAlignOf(SizeofCmsghdr)))
+}
+
+// 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))
+	data := cmsgData(h)
+	for _, fd := range fds {
+		*(*int32)(data) = int32(fd)
+		data = unsafe.Pointer(uintptr(data) + 4)
+	}
+	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
+}