const golang.org/x/sys/unix.UDP_ENCAP_L2TPINUDP

one use

	golang.org/x/sys/unix (current package)
		zerrors_linux.go#L3545: 	UDP_ENCAP_L2TPINUDP                         = 0x3

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