References: golang.org/x/sys/unix.ESP_V6

const golang.org/x/sys/unix.ESP_V6_FLOW

one use

	golang.org/x/sys/unix (current package)
		ztypes_linux.go#L4147: 	ESP_V6_FLOW    = 0xc

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