rings: introduce AddrToU32() and AddrFromU32() helpers

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

pkg/rings/cidr.go

@@ -0,0 +1,43 @@
+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
+}

pkg/rings/cidr_test.go

@@ -0,0 +1,92 @@
+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
+}