Support FreeBSD on pkg/mount

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)

mount/mounter_freebsd.go

@@ -0,0 +1,59 @@
+package mount
+
+/*
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/_iovec.h>
+#include <sys/mount.h>
+#include <sys/param.h>
+*/
+import "C"
+
+import (
+	"fmt"
+	"strings"
+	"syscall"
+	"unsafe"
+)
+
+func allocateIOVecs(options []string) []C.struct_iovec {
+	out := make([]C.struct_iovec, len(options))
+	for i, option := range options {
+		out[i].iov_base = unsafe.Pointer(C.CString(option))
+		out[i].iov_len = C.size_t(len(option) + 1)
+	}
+	return out
+}
+
+func mount(device, target, mType string, flag uintptr, data string) error {
+	isNullFS := false
+
+	xs := strings.Split(data, ",")
+	for _, x := range xs {
+		if x == "bind" {
+			isNullFS = true
+		}
+	}
+
+	options := []string{"fspath", target}
+	if isNullFS {
+		options = append(options, "fstype", "nullfs", "target", device)
+	} else {
+		options = append(options, "fstype", mType, "from", device)
+	}
+	rawOptions := allocateIOVecs(options)
+	for _, rawOption := range rawOptions {
+		defer C.free(rawOption.iov_base)
+	}
+
+	if errno := C.nmount(&rawOptions[0], C.uint(len(options)), C.int(flag)); errno != 0 {
+		reason := C.GoString(C.strerror(*C.__error()))
+		return fmt.Errorf("Failed to call nmount: %s", reason)
+	}
+	return nil
+}
+
+func unmount(target string, flag int) error {
+	return syscall.Unmount(target, flag)
+}