func cmsgAlignOf(salen int) int {
	salign := SizeofPtr
	switch runtime.GOOS {
	case "darwin", "dragonfly", "solaris":
		if SizeofPtr == 8 {
			salign = 4
		}
	case "openbsd":
		if runtime.GOARCH == "arm" {
			salign = 8
		}
	}
	return (salen + salign - 1) & ^(salign - 1)
}
Round the length of a raw sockaddr up to align it properly.
package unix
import (
	"runtime"
	"unsafe"
)