rings: RingTwoPrefix()

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

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

.gitignore

@@ -1 +1,2 @@
 .tmp
+.version

cmd/jpictl/main.go

@@ -2,6 +2,8 @@
 package main
 
 import (
+	_ "embed"
+
 	"github.com/spf13/cobra"
 )
 
@@ -12,8 +14,9 @@ const (
 
 var (
 	rootCmd = &cobra.Command{
-		Use:   CmdName,
-		Short: "control tool for jpi.cloud",
+		Use:     CmdName,
+		Short:   "control tool for jpi.cloud",
+		Version: version,
 	}
 )
 

cmd/jpictl/version.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	_ "embed"
+
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+//go:generate sh -c "git describe | tr -d '\r\n' > .version"
+//go:embed .version
+var version string
+
+var versionCmd = &cobra.Command{
+	Use:   "version",
+	Short: "Returns jpictl's version",
+	Args:  cobra.NoArgs,
+	Run: func(_ *cobra.Command, _ []string) {
+		_, _ = fmt.Fprintf(os.Stdout, "%s\n", version)
+	},
+}
+
+func init() {
+	if version == "" {
+		version = "undetermined"
+	}
+
+	rootCmd.AddCommand(versionCmd)
+}

pkg/ceph/config.go

@@ -39,6 +39,9 @@ func writeGlobalToBuffer(w *bytes.Buffer, c *GlobalConfig) {
 	_, _ = fmt.Fprintf(w, "%s = %s\n", "mon_initial_members", strings.Join(c.Monitors, ", "))
 	_, _ = fmt.Fprintf(w, "%s = %s\n", "mon_host", joinAddrs(c.MonitorsAddr, ", "))
 	_, _ = fmt.Fprintf(w, "%s = %s\n", "cluster_network", c.ClusterNetwork.String())
+
+	_, _ = fmt.Fprintf(w, "\n; %s\n", "don't rewrite labels on startup")
+	_, _ = fmt.Fprintf(w, "%s = %s\n", "osd_class_update_on_start", "false")
 }
 
 func joinAddrs(addrs []netip.Addr, sep string) string {

pkg/cluster/cluster_scan.go

@@ -4,6 +4,7 @@ import (
 	"io/fs"
 	"path"
 	"sort"
+	"strings"
 
 	"darvaza.org/core"
 )
@@ -12,6 +13,10 @@ const (
 	// ZoneRegionsFileName indicates the file containing
 	// region names as references
 	ZoneRegionsFileName = "regions"
+
+	// RegionClusterTokenFileName contains the kubernetes
+	// token of the cluster this region represents
+	RegionClusterTokenFileName = "k8s_token"
 )
 
 func (m *Cluster) scan(opts *ScanOptions) error {
@@ -186,6 +191,8 @@ func (z *Zone) scan() error {
 		switch {
 		case name == ZoneRegionsFileName:
 			err = z.loadRegions()
+		case name == RegionClusterTokenFileName:
+			err = z.loadClusterToken()
 		case e.IsDir():
 			err = z.scanSubdirectory(name)
 		default:
@@ -218,6 +225,32 @@ func (z *Zone) loadRegions() error {
 	return err
 }
 
+func (z *Zone) loadClusterToken() error {
+	var token string
+
+	filename := path.Join(z.Name, RegionClusterTokenFileName)
+	lines, err := z.zones.ReadLines(filename)
+	if err != nil {
+		return err
+	}
+
+	// first non-empty line
+	for _, s := range lines {
+		s = strings.TrimSpace(s)
+		if s != "" {
+			token = s
+			break
+		}
+	}
+
+	err = z.zones.setRegionClusterToken(z.Name, token)
+	if err != nil {
+		err = core.Wrap(err, filename)
+	}
+
+	return err
+}
+
 func (z *Zone) scanSubdirectory(name string) error {
 	m := &Machine{
 		zone:   z,

pkg/cluster/env.go

@@ -4,12 +4,14 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"sort"
 	"strings"
 )
 
 // Env is a shell environment factory for this cluster
 type Env struct {
 	ZoneIterator
+	RegionIterator
 
 	cephFSID string
 	export   bool
@@ -23,9 +25,10 @@ func (m *Cluster) Env(export bool) (*Env, error) {
 	}
 
 	env := &Env{
-		ZoneIterator: m,
-		cephFSID:     fsid.String(),
-		export:       export,
+		ZoneIterator:   m,
+		RegionIterator: m,
+		cephFSID:       fsid.String(),
+		export:         export,
 	}
 
 	return env, nil
@@ -43,6 +46,22 @@ func (m *Env) Zones() []int {
 	return zones
 }
 
+// Regions returns the list of primary regions
+func (m *Env) Regions() []string {
+	var regions []string
+
+	m.ForEachRegion(func(r *Region) bool {
+		if r.Cluster != nil {
+			regions = append(regions, r.Name)
+		}
+
+		return false
+	})
+
+	sort.Strings(regions)
+	return regions
+}
+
 // WriteTo generates environment variables for shell scripts
 func (m *Env) WriteTo(w io.Writer) (int64, error) {
 	var buf bytes.Buffer
@@ -51,6 +70,7 @@ func (m *Env) WriteTo(w io.Writer) (int64, error) {
 		m.writeEnvVar(&buf, m.cephFSID, "FSID")
 	}
 
+	m.writeEnvVarStrings(&buf, m.Regions(), "REGIONS")
 	m.writeEnvVarInts(&buf, m.Zones(), "ZONES")
 
 	m.ForEachZone(func(z *Zone) bool {
@@ -74,6 +94,9 @@ func (m *Env) writeEnvZone(w io.Writer, z *Zone) {
 	gateways, _ := z.GatewayIDs()
 	m.writeEnvVarInts(w, gateways, "ZONE%v_%s", zoneID, "GW")
 
+	// ZONE{zoneID}_REGION
+	m.writeEnvVar(w, genEnvZoneRegion(z), "ZONE%v_%s", zoneID, "REGION")
+
 	// Ceph
 	monitors := z.GetCephMonitors()
 	// MON{zoneID}_NAME
@@ -85,22 +108,29 @@ func (m *Env) writeEnvZone(w io.Writer, z *Zone) {
 }
 
 func (m *Env) writeEnvVarInts(w io.Writer, value []int, name string, args ...any) {
-	var s string
+	var buf bytes.Buffer
 
-	if n := len(value); n > 0 {
-		var buf bytes.Buffer
-
-		for i, v := range value {
-			if i != 0 {
-				_, _ = fmt.Fprint(&buf, " ")
-			}
-			_, _ = fmt.Fprintf(&buf, "%v", v)
+	for _, v := range value {
+		if buf.Len() > 0 {
+			_, _ = fmt.Fprint(&buf, " ")
 		}
-
-		s = buf.String()
+		_, _ = fmt.Fprintf(&buf, "%v", v)
 	}
 
-	m.writeEnvVar(w, s, name, args...)
+	m.writeEnvVar(w, buf.String(), name, args...)
+}
+
+func (m *Env) writeEnvVarStrings(w io.Writer, value []string, name string, args ...any) {
+	var buf bytes.Buffer
+
+	for _, v := range value {
+		if buf.Len() > 0 {
+			_, _ = fmt.Fprint(&buf, " ")
+		}
+		_, _ = fmt.Fprintf(&buf, "%s", v)
+	}
+
+	m.writeEnvVar(w, buf.String(), name, args...)
 }
 
 func (m *Env) writeEnvVar(w io.Writer, value string, name string, args ...any) {
@@ -117,7 +147,11 @@ func (m *Env) writeEnvVar(w io.Writer, value string, name string, args ...any) {
 	if name != "" {
 		value = strings.TrimSpace(value)
 
-		_, _ = fmt.Fprintf(w, "%s%s=%q\n", prefix, name, value)
+		if value == "" {
+			_, _ = fmt.Fprintf(w, "%s%s=\n", prefix, name)
+		} else {
+			_, _ = fmt.Fprintf(w, "%s%s=%q\n", prefix, name, value)
+		}
 	}
 }
 
@@ -135,6 +169,21 @@ func genEnvZoneNodes(z *Zone) string {
 	return ""
 }
 
+func genEnvZoneRegion(z *Zone) string {
+	var region string
+
+	z.ForEachRegion(func(r *Region) bool {
+		if r.Cluster != nil {
+			region = r.Name
+			return true
+		}
+
+		return false
+	})
+
+	return region
+}
+
 func genEnvZoneCephMonNames(m Machines) string {
 	var buf strings.Builder
 	m.ForEachMachine(func(p *Machine) bool {

pkg/cluster/regions.go

@@ -8,14 +8,23 @@ import (
 var (
 	_ MachineIterator = (*Region)(nil)
 	_ ZoneIterator    = (*Region)(nil)
+
+	_ RegionIterator = (*Zone)(nil)
+	_ RegionIterator = (*Cluster)(nil)
 )
 
+// A RegionIterator is a set of Regions we can iterate on
+type RegionIterator interface {
+	ForEachRegion(func(*Region) bool)
+}
+
 // Region represents a group of zones geographically related
 type Region struct {
 	m     *Cluster
 	zones []*Zone
 
 	Name    string
+	Cluster *string  `json:",omitempty" yaml:",omitempty"`
 	Regions []string `json:",omitempty" yaml:",omitempty"`
 }
 
@@ -106,6 +115,26 @@ func (m *Cluster) setRegionZones(name string, zones ...*Zone) {
 	})
 }
 
+func (m *Cluster) setRegionClusterToken(name string, token string) error {
+	for i := range m.Regions {
+		r := &m.Regions[i]
+
+		if r.Name == name {
+			// found
+			r.Cluster = &token
+			return nil
+		}
+	}
+
+	// new
+	m.Regions = append(m.Regions, Region{
+		m:       m,
+		Name:    name,
+		Cluster: &token,
+	})
+	return nil
+}
+
 func (m *Cluster) appendRegionRegions(name string, subs ...string) {
 	for i := range m.Regions {
 		r := &m.Regions[i]
@@ -124,6 +153,28 @@ func (m *Cluster) appendRegionRegions(name string, subs ...string) {
 	})
 }
 
+// ForEachRegion calls a function on all regions this zone belongs to.
+func (z *Zone) ForEachRegion(fn func(*Region) bool) {
+	if fn == nil {
+		return
+	}
+
+	z.zones.ForEachRegion(func(r *Region) bool {
+		var match bool
+
+		r.ForEachZone(func(z2 *Zone) bool {
+			match = (z == z2)
+			return match
+		})
+
+		if match && fn(r) {
+			return true
+		}
+
+		return false
+	})
+}
+
 func (z *Zone) appendRegions(regions ...string) error {
 	for _, s := range regions {
 		// TODO: validate
@@ -147,7 +198,7 @@ func (m *Cluster) finishRegion(r *Region) {
 	r.m = m
 	sub := []string{}
 	for _, name := range r.Regions {
-		r2, ok := m.getRegion(name)
+		r2, ok := m.getFinishRegion(name)
 		if !ok {
 			m.warn(nil).WithField("region", name).Print("unknown region")
 			continue
@@ -162,9 +213,7 @@ func (m *Cluster) finishRegion(r *Region) {
 func (m *Cluster) getRegion(name string) (*Region, bool) {
 	for i := range m.Regions {
 		r := &m.Regions[i]
-
 		if name == r.Name {
-			m.finishRegion(r)
 			return r, true
 		}
 	}
@@ -172,17 +221,22 @@ func (m *Cluster) getRegion(name string) (*Region, bool) {
 	return nil, false
 }
 
+func (m *Cluster) getFinishRegion(name string) (*Region, bool) {
+	if r, ok := m.getRegion(name); ok {
+		m.finishRegion(r)
+		return r, true
+	}
+
+	return nil, false
+}
+
 // SyncRegions writes to the file system the regions this [Zone]
 // belongs to.
 func (z *Zone) SyncRegions() error {
 	err := z.syncZoneRegions()
 	if err == nil {
 		z.ForEachMachine(func(p *Machine) bool {
-			if p.IsActive() {
-				err = p.RemoveFile("region")
-			} else {
-				err = p.WriteStringFile("none\n", "region")
-			}
+			err = z.syncMachineRegions(p)
 			return err != nil
 		})
 	}
@@ -190,8 +244,24 @@ func (z *Zone) SyncRegions() error {
 	return err
 }
 
+func (*Zone) syncMachineRegions(p *Machine) error {
+	var err error
+
+	if p.IsActive() {
+		err = p.RemoveFile("region")
+	} else {
+		err = p.WriteStringFile("none\n", "region")
+	}
+
+	if err == nil {
+		err = p.RemoveFile(RegionClusterTokenFileName)
+	}
+
+	return err
+}
+
 func (z *Zone) syncZoneRegions() error {
-	name := filepath.Join(z.Name, "regions")
+	name := filepath.Join(z.Name, ZoneRegionsFileName)
 
 	if len(z.Regions) > 0 {
 		var buf bytes.Buffer
@@ -210,9 +280,25 @@ func (z *Zone) syncZoneRegions() error {
 // SyncRegions writes to the file system the regions covered
 // by this meta-region
 func (r *Region) SyncRegions() error {
-	name := filepath.Join(r.Name, "regions")
+	if err := r.syncRegionsFile(); err != nil {
+		return err
+	}
 
-	if len(r.Regions) > 0 {
+	return r.syncClusterFile()
+}
+
+func (r *Region) mkdir() error {
+	return r.m.MkdirAll(r.Name)
+}
+
+func (r *Region) syncRegionsFile() error {
+	var err error
+
+	name := filepath.Join(r.Name, ZoneRegionsFileName)
+
+	if len(r.Regions) == 0 {
+		err = r.m.RemoveFile(name)
+	} else if err = r.mkdir(); err == nil {
 		var buf bytes.Buffer
 
 		for _, s := range r.Regions {
@@ -220,12 +306,29 @@ func (r *Region) SyncRegions() error {
 			_, _ = buf.WriteRune('\n')
 		}
 
-		if err := r.m.MkdirAll(r.Name); err != nil {
-			return err
-		}
-
-		return r.m.WriteStringFile(buf.String(), name)
+		err = r.m.WriteStringFile(buf.String(), name)
 	}
 
-	return r.m.RemoveFile(name)
+	return err
+}
+
+func (r *Region) syncClusterFile() error {
+	var err error
+
+	name := filepath.Join(r.Name, RegionClusterTokenFileName)
+
+	if r.Cluster == nil {
+		err = r.m.RemoveFile(name)
+	} else if err = r.mkdir(); err == nil {
+		var buf bytes.Buffer
+
+		_, _ = buf.WriteString(*r.Cluster)
+		if buf.Len() > 0 {
+			_, _ = buf.WriteRune('\n')
+		}
+
+		err = r.m.WriteStringFile(buf.String(), name)
+	}
+
+	return err
 }

pkg/rings/cidr.go

@@ -0,0 +1,77 @@
+package rings
+
+import "net/netip"
+
+// AddrFromU32 converts a 32bit value into an IPv4
+// address.
+func AddrFromU32(v uint32) netip.Addr {
+	return AddrFrom4(
+		uint(v>>24),
+		uint(v>>16),
+		uint(v>>8),
+		uint(v),
+	)
+}
+
+// AddrFrom4 assembles an IPv4 address for 4 numbers.
+// each number is truncated to 8-bits.
+func AddrFrom4(a, b, c, d uint) netip.Addr {
+	return netip.AddrFrom4([4]byte{
+		byte(a & 0xff),
+		byte(b & 0xff),
+		byte(c & 0xff),
+		byte(d & 0xff),
+	})
+}
+
+// AddrToU32 converts a valid IPv4 address into it's
+// 32bit numeric representation.
+func AddrToU32(addr netip.Addr) (v uint32, ok bool) {
+	if addr.IsValid() {
+		if addr.Is4() || addr.Is4In6() {
+			a4 := addr.As4()
+
+			v = uint32(a4[0])<<24 +
+				uint32(a4[1])<<16 +
+				uint32(a4[2])<<8 +
+				uint32(a4[3])
+			return v, true
+		}
+	}
+
+	return 0, false
+}
+
+// PrefixToRange returns the beginning and end of a
+// [netip.Prefix] (aka CIDR or subnet).
+func PrefixToRange(subnet netip.Prefix) (from, to netip.Addr, ok bool) {
+	var u uint32
+
+	addr := subnet.Addr()
+	if u, ok = AddrToU32(addr); ok {
+		bits := subnet.Bits()
+
+		switch {
+		case bits > 32, bits < 0:
+			// bad
+		case bits == 32:
+			// single
+			from, to, ok = addr, addr, true
+		default:
+			// subnet
+			shift := 32 - bits
+
+			m1 := uint32((1 << shift) - 1)
+			m0 := uint32(0xffffffff) & ^m1
+
+			u0 := u & m0
+			u1 := u0 + m1
+
+			ok = true
+			from = AddrFromU32(u0)
+			to = AddrFromU32(u1)
+		}
+	}
+
+	return from, to, ok
+}

pkg/rings/cidr_test.go

@@ -0,0 +1,178 @@
+package rings
+
+import (
+	"fmt"
+	"net/netip"
+	"testing"
+)
+
+func TestAddrFrom4(t *testing.T) {
+	cases := []struct {
+		v [4]uint
+		s string
+	}{
+		{[4]uint{0, 0, 0, 0}, "0.0.0.0"},
+		{[4]uint{127, 0, 0, 1}, "127.0.0.1"},
+		{[4]uint{4096 + 127, 0, 0, 1}, "127.0.0.1"},
+		{[4]uint{257, 258, 259, 260}, "1.2.3.4"},
+		{[4]uint{255, 255, 255, 255}, "255.255.255.255"},
+	}
+
+	for i, tc := range cases {
+		fn := fmt.Sprintf("%v.%v.%v.%v", tc.v[0], tc.v[1], tc.v[2], tc.v[3])
+		addr := AddrFrom4(tc.v[0], tc.v[1], tc.v[2], tc.v[3])
+		s := addr.String()
+
+		if s == tc.s {
+			t.Logf("[%v/%v]: %s → %s", i, len(cases), fn, s)
+		} else {
+			t.Errorf("ERROR: [%v/%v]: %s → %s (expected %s)", i, len(cases), fn, s, tc.s)
+		}
+	}
+}
+
+func TestAddrU32Invalid(t *testing.T) {
+	cases := []netip.Addr{
+		{},
+		netip.IPv6Unspecified(),
+		netip.IPv6Loopback(),
+	}
+
+	for i, tc := range cases {
+		v, ok := AddrToU32(tc)
+		switch {
+		case !ok && v == 0:
+			t.Logf("[%v/%v]: %s → %v %v", i, len(cases), tc, 0, false)
+		default:
+			t.Errorf("ERROR: [%v/%v]: %s → %v %v (expected %v %v)", i, len(cases),
+				tc, v, ok, 0, false)
+		}
+	}
+}
+
+func TestAddrU32Valid(t *testing.T) {
+	cases := []netip.Addr{
+		netip.IPv4Unspecified(),
+		AddrFrom4(0, 0, 0, 0),
+		AddrFrom4(1, 2, 3, 4),
+		AddrFrom4(10, 20, 30, 40),
+		AddrFrom4(127, 0, 0, 1),
+		AddrFrom4(255, 255, 255, 255),
+		MustParseAddr("::ffff:1.2.3.4"),
+	}
+
+	for i, tc := range cases {
+		u32, ok := AddrToU32(tc)
+		if !ok {
+			t.Errorf("ERROR: [%v/%v]: %s → %v %v", i, len(cases), tc, u32, ok)
+			continue
+		}
+
+		addr := AddrFromU32(u32)
+		if tc.Is4In6() {
+			ok = addr.Compare(tc.Unmap()) == 0
+		} else {
+			ok = addr.Compare(tc) == 0
+		}
+
+		if ok {
+			t.Logf("[%v/%v]: %s → %v → %s", i, len(cases), tc, u32, addr)
+		} else {
+			t.Errorf("ERROR: [%v/%v]: %s → %v → %s", i, len(cases), tc, u32, addr)
+		}
+	}
+}
+
+func MustParseAddr(s string) netip.Addr {
+	addr, err := netip.ParseAddr(s)
+	if err != nil {
+		panic(err)
+	}
+	return addr
+}
+
+func MustParsePrefix(s string) netip.Prefix {
+	subnet, err := netip.ParsePrefix(s)
+	if err != nil {
+		panic(err)
+	}
+	return subnet
+}
+
+func TestPrefixToRangeValid(t *testing.T) {
+	cases := []struct {
+		subnet netip.Prefix
+		from   netip.Addr
+		to     netip.Addr
+	}{
+		{
+			MustParsePrefix("127.0.0.1/32"),
+			MustParseAddr("127.0.0.1"),
+			MustParseAddr("127.0.0.1"),
+		},
+		{
+			MustParsePrefix("127.0.0.1/24"),
+			MustParseAddr("127.0.0.0"),
+			MustParseAddr("127.0.0.255"),
+		},
+		{
+			MustParsePrefix("127.0.1.2/16"),
+			MustParseAddr("127.0.0.0"),
+			MustParseAddr("127.0.255.255"),
+		},
+		{
+			MustParsePrefix("127.1.2.3/8"),
+			MustParseAddr("127.0.0.0"),
+			MustParseAddr("127.255.255.255"),
+		},
+		{
+			MustParsePrefix("10.20.30.40/12"),
+			MustParseAddr("10.16.0.0"),
+			MustParseAddr("10.31.255.255"),
+		},
+		{
+			MustParsePrefix("10.20.30.40/20"),
+			MustParseAddr("10.20.16.0"),
+			MustParseAddr("10.20.31.255"),
+		},
+		{
+			MustParsePrefix("10.0.0.0/12"),
+			MustParseAddr("10.0.0.0"),
+			MustParseAddr("10.15.255.255"),
+		},
+		{
+			MustParsePrefix("10.16.0.0/12"),
+			MustParseAddr("10.16.0.0"),
+			MustParseAddr("10.31.255.255"),
+		},
+		{
+			MustParsePrefix("10.32.0.0/12"),
+			MustParseAddr("10.32.0.0"),
+			MustParseAddr("10.47.255.255"),
+		},
+		{
+			MustParsePrefix("10.48.0.0/12"),
+			MustParseAddr("10.48.0.0"),
+			MustParseAddr("10.63.255.255"),
+		},
+	}
+
+	for i, tc := range cases {
+		from, to, ok := PrefixToRange(tc.subnet)
+		if ok && from.IsValid() && to.IsValid() &&
+			from.Compare(tc.from) == 0 &&
+			to.Compare(tc.to) == 0 {
+			//
+			t.Logf("[%v/%v]: %s → %s - %s",
+				i, len(cases),
+				tc.subnet,
+				from, to)
+		} else {
+			t.Errorf("ERROR: [%v/%v]: %q → %s - %s %v (expected %s - %s %v)",
+				i, len(cases),
+				tc.subnet,
+				from, to, ok,
+				tc.from, tc.to, true)
+		}
+	}
+}

pkg/rings/rings.go

@@ -0,0 +1,204 @@
+// Package rings provides logic to work with the four rings
+// of a cluster
+package rings
+
+import (
+	"net/netip"
+	"syscall"
+
+	"darvaza.org/core"
+)
+
+const (
+	// RegionMax indicates the highest number that can be used for a [RegionID].
+	RegionMax = (1 << 4) - 1
+	// ZoneMax indicates the highest number that can be used for a [ZoneID].
+	ZoneMax = (1 << 4) - 1
+	// NodeMax indicates the highest number that can be used for a [NodeID].
+	NodeMax = (1 << 12) - 1
+	// NodeZeroMax indicates the highest number that can be used for a [NodeID]
+	// when its a gateway connected to Ring 0 (backbone).
+	NodeZeroMax = (1 << 8) - 1
+
+	// RingZeroBits indicates the size of the prefix on the ring 0 (backbone) network.
+	RingZeroBits = 16
+	// RingOneBits indicates the size of the prefix on the ring 1 (lan) network.
+	RingOneBits = 20
+	// RingTwoBits indicates the size of the prefix on the ring 2 (services) network
+	// of all kubernetes clusters.
+	RingTwoBits = 20
+	// RingThreeBits indicates the size of the prefix on the ring 3 (pods) network
+	// of the kubernetes cluster of a region.
+	RingThreeBits = 12
+)
+
+// RegionID is the identifier of a region, valid between 1 and [RegionMax].
+type RegionID int
+
+// Valid tells a [RegionID] is within the valid range.
+func (n RegionID) Valid() bool { return n > 0 && n <= RegionMax }
+
+// ZoneID is the identifier of a zone within a region, valid between 1 and [ZoneMax].
+type ZoneID int
+
+// Valid tells a [ZoneID] is within the valid range.
+func (n ZoneID) Valid() bool { return n > 0 && n <= ZoneMax }
+
+// NodeID is the identifier of a machine within a zone of a region, valid between
+// 1 and [NodeMax], but between 1 and [NodeZeroMax] if it will be a zone gateway.
+type NodeID int
+
+// Valid tells a [NodeID] is within the valid range.
+func (n NodeID) Valid() bool { return n > 0 && n <= NodeMax }
+
+// ValidZero tells a [NodeID] is within the valid range for a gateway.
+func (n NodeID) ValidZero() bool { return n > 0 && n <= NodeZeroMax }
+
+// ErrOutOfRange is an error indicating the value of a field
+// is out of range.
+func ErrOutOfRange[T ~int | ~uint32](value T, field string) error {
+	return core.Wrap(syscall.EINVAL, "%s out of range (%v)", field, value)
+}
+
+// RingZeroPrefix represents the backbone that connects gateways
+// of the different Ring 1 networks.
+//
+// The ring 0 network corresponds to what would be ring 2 for region_id 0.
+// 10.0.0.0-10.0.255.255
+func RingZeroPrefix(region RegionID, zone ZoneID) (cidr netip.Prefix, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	case !zone.Valid():
+		err = ErrOutOfRange(zone, "zone")
+	default:
+		addr := unsafeRingZeroAddress(region, zone, 0)
+		cidr = netip.PrefixFrom(addr, RingZeroBits)
+	}
+
+	return cidr, err
+}
+
+// RingZeroAddress returns a Ring 0 address for a particular node.
+//
+// A ring 0 address looks like 10.0.(region_id << 4 + zone_id).(node_id)/20
+func RingZeroAddress(region RegionID, zone ZoneID, node NodeID) (addr netip.Addr, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	case !zone.Valid():
+		err = ErrOutOfRange(zone, "zone")
+	case !node.ValidZero():
+		err = ErrOutOfRange(node, "node")
+	default:
+		addr = unsafeRingZeroAddress(region, zone, node)
+	}
+
+	return addr, err
+}
+
+// RingOnePrefix represents a (virtual) local network of a zone.
+//
+// Ring 1 is `10.(region_id).(zone_id << 4).(node_id)/20` network
+// grouped under what would be Ring 2 for region_id 0.
+// There are 12 bits worth of nodes but nodes under 255 are special
+// as they also get a slot on Ring 0.
+func RingOnePrefix(region RegionID, zone ZoneID) (cidr netip.Prefix, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	case !zone.Valid():
+		err = ErrOutOfRange(zone, "zone")
+	default:
+		addr := unsafeRingOneAddress(region, zone, 0)
+		cidr = netip.PrefixFrom(addr, RingOneBits)
+	}
+	return cidr, err
+}
+
+// RingOneAddress returns a Ring 1 address for a particular node.
+//
+// A ring 1 address is `10.(region_id).(zone_id << 4).(node_id)/20`
+// but the node_id can take up to 12 bits.
+func RingOneAddress(region RegionID, zone ZoneID, node NodeID) (addr netip.Addr, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	case !zone.Valid():
+		err = ErrOutOfRange(zone, "zone")
+	case !node.Valid():
+		err = ErrOutOfRange(node, "node")
+	default:
+		addr = unsafeRingOneAddress(region, zone, node)
+	}
+	return addr, err
+}
+
+// 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 := unsafeRingTwoAddress(region, 0)
+		cidr = netip.PrefixFrom(addr, RingTwoBits)
+	}
+	return cidr, err
+}
+
+// RingThreePrefix returns the subnet corresponding to
+// the pods of a cluster.
+//
+// Ring 3 is a `10.(region_id << 4).0.0/12` network
+func RingThreePrefix(region RegionID) (subnet netip.Prefix, err error) {
+	switch {
+	case !region.Valid():
+		err = ErrOutOfRange(region, "region")
+	default:
+		addr := unsafeRingThreeAddress(region, 0)
+		subnet = netip.PrefixFrom(addr, RingThreeBits)
+	}
+	return subnet, err
+}
+
+func unsafeRingZeroAddress(region RegionID, zone ZoneID, node NodeID) netip.Addr {
+	r := uint(region)
+	z := uint(zone)
+	n := uint(node)
+
+	return AddrFrom4(10, 0, r<<4+z, n)
+}
+
+func unsafeRingOneAddress(region RegionID, zone ZoneID, node NodeID) netip.Addr {
+	r := uint(region)
+	z := uint(zone)
+	n := uint(node)
+
+	n1 := n >> 8
+	n0 := n >> 0
+
+	return AddrFrom4(10, r, z<<4+n1, n0)
+}
+
+func unsafeRingTwoAddress(region RegionID, n uint) netip.Addr {
+	r := uint(region)
+
+	n1 := n >> 8
+	n0 := n >> 0
+
+	return AddrFrom4(10, r, n1, n0)
+}
+
+func unsafeRingThreeAddress(region RegionID, n uint) netip.Addr {
+	r := uint(region)
+
+	n2 := n >> 16
+	n1 := n >> 8
+	n0 := n >> 0
+
+	return AddrFrom4(10, r<<4+n2, n1, n0)
+}

pkg/rings/rings_test.go

@@ -0,0 +1,63 @@
+package rings
+
+import (
+	"fmt"
+	"net/netip"
+	"testing"
+)
+
+func TestRingZeroAddress(t *testing.T) {
+	RZNTest(t, "RingZeroAddress", RingZeroAddress, []RZNTestCase{
+		{1, 1, 50, MustParseAddr("10.0.17.50")},
+		{1, 2, 50, MustParseAddr("10.0.18.50")},
+		{2, 3, 1, MustParseAddr("10.0.35.1")},
+		{2, 3, 300, netip.Addr{}},
+	})
+}
+
+func TestRingOneAddress(t *testing.T) {
+	RZNTest(t, "RingOneAddress", RingOneAddress, []RZNTestCase{
+		{1, 1, 50, MustParseAddr("10.1.16.50")},
+		{1, 2, 50, MustParseAddr("10.1.32.50")},
+		{2, 3, 300, MustParseAddr("10.2.49.44")},
+		{1, 20, 50, netip.Addr{}},
+	})
+}
+
+type RZNTestCase struct {
+	region RegionID
+	zone   ZoneID
+	node   NodeID
+	addr   netip.Addr
+}
+
+func RZNTest(t *testing.T,
+	fnName string, fn func(RegionID, ZoneID, NodeID) (netip.Addr, error),
+	cases []RZNTestCase) {
+	//
+	for i, tc := range cases {
+		s := fmt.Sprintf("%s(%v, %v, %v)", fnName,
+			tc.region,
+			tc.zone,
+			tc.node,
+		)
+
+		addr, err := fn(tc.region, tc.zone, tc.node)
+
+		switch {
+		case !tc.addr.IsValid():
+			// expect error
+			if err != nil {
+				t.Logf("[%v/%v]: %s → %s", i, len(cases), s, err)
+			} else {
+				t.Errorf("ERROR: [%v/%v]: %s → %s (expected %s)", i, len(cases), s, addr, "error")
+			}
+		case err != nil:
+			t.Errorf("ERROR: [%v/%v]: %s → %s (expected %s)", i, len(cases), s, err, tc.addr)
+		case addr.Compare(tc.addr) != 0:
+			t.Errorf("ERROR: [%v/%v]: %s → %s (expected %s)", i, len(cases), s, addr, tc.addr)
+		default:
+			t.Logf("[%v/%v]: %s → %s", i, len(cases), s, addr)
+		}
+	}
+}