const golang.org/x/sys/unix.IPV6_FLOWLABEL_MASK

one use

	golang.org/x/sys/unix (current package)
		zerrors_linux_amd64.go#L121: 	IPV6_FLOWLABEL_MASK              = 0xffff0f00

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