const golang.org/x/sys/unix.UDP_ENCAP_GTP0

one use

	golang.org/x/sys/unix (current package)
		zerrors_linux.go#L3543: 	UDP_ENCAP_GTP0                              = 0x4

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