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 +1,3 @@
+// Package rings provides logic to work with the four rings
+// of a cluster
+package rings