const golang.org/x/sys/unix.SizeofIfMsghdr

one use

	golang.org/x/sys/unix (current package)
		ztypes_darwin_arm64.go#L296: 	SizeofIfMsghdr    = 0x70

The pages are generated with Golds v0.2.8-preview. (GOOS=darwin GOARCH=arm64)