References: golang.org/x/sys/unix.UDP_V4

const golang.org/x/sys/unix.UDP_V4_FLOW

one use

	golang.org/x/sys/unix (current package)
		ztypes_linux.go#L4143: 	UDP_V4_FLOW    = 0x2

The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)