rings: RingTwoPrefix()

Ring 2 is the service network shared by all kubernetes clusters.

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/rings/two.go

@@ -0,0 +1,19 @@
+package rings
+
+import "net/netip"
+
+// RingTwoPrefix represents the services of a cluster
+//
+// Ring 2 subnets are of the form `10.(region_id).0.0/20`,
+// using the address space that would belong to the ring 3
+// region_id 0.
+func RingTwoPrefix(region RegionID) (cidr netip.Prefix, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	default:
+		addr := AddrFrom4(10, uint(region), 0, 0)
+		cidr = netip.PrefixFrom(addr, RingTwoBits)
+	}
+	return cidr, err
+}