pkg/mesh: fix ip allocator helper

This commit fixes the ip allocator `newAllocator` to produce IP
addresses with the original network mask. This is makes more sense. The
original functionality can be reproduced by wrapping the produced IP
address with the `oneAddressCIDR` helper.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

pkg/mesh/ip.go

@@ -337,12 +337,13 @@ func defaultInterface() (*net.Interface, error) {
 
 type allocator struct {
 	bits    int
+	ones    int
 	cidr    *net.IPNet
 	current net.IP
 }
 
 func newAllocator(cidr net.IPNet) *allocator {
-	_, bits := cidr.Mask.Size()
+	ones, bits := cidr.Mask.Size()
 	current := make(net.IP, len(cidr.IP))
 	copy(current, cidr.IP)
 	if ip4 := current.To4(); ip4 != nil {
@@ -351,6 +352,7 @@ func newAllocator(cidr net.IPNet) *allocator {
 
 	return &allocator{
 		bits:    bits,
+		ones:    ones,
 		cidr:    &cidr,
 		current: current,
 	}
@@ -373,5 +375,5 @@ func (a *allocator) next() *net.IPNet {
 	ip := make(net.IP, len(a.current))
 	copy(ip, a.current)
 
-	return &net.IPNet{IP: ip, Mask: net.CIDRMask(a.bits, a.bits)}
+	return &net.IPNet{IP: ip, Mask: net.CIDRMask(a.ones, a.bits)}
 }

pkg/mesh/ip_test.go

@@ -19,6 +19,60 @@ import (
 	"testing"
 )
 
+func TestNewAllocator(t *testing.T) {
+	_, c1, err := net.ParseCIDR("10.1.0.0/16")
+	if err != nil {
+		t.Fatalf("failed to parse CIDR: %v", err)
+	}
+	a1 := newAllocator(*c1)
+	_, c2, err := net.ParseCIDR("10.1.0.0/32")
+	if err != nil {
+		t.Fatalf("failed to parse CIDR: %v", err)
+	}
+	a2 := newAllocator(*c2)
+	_, c3, err := net.ParseCIDR("10.1.0.0/31")
+	if err != nil {
+		t.Fatalf("failed to parse CIDR: %v", err)
+	}
+	a3 := newAllocator(*c3)
+	for _, tc := range []struct {
+		name string
+		a    *allocator
+		next string
+	}{
+		{
+			name: "10.1.0.0/16 first",
+			a:    a1,
+			next: "10.1.0.1/16",
+		},
+		{
+			name: "10.1.0.0/16 second",
+			a:    a1,
+			next: "10.1.0.2/16",
+		},
+		{
+			name: "10.1.0.0/32",
+			a:    a2,
+			next: "<nil>",
+		},
+		{
+			name: "10.1.0.0/31 first",
+			a:    a3,
+			next: "10.1.0.1/31",
+		},
+		{
+			name: "10.1.0.0/31 second",
+			a:    a3,
+			next: "<nil>",
+		},
+	} {
+		next := tc.a.next()
+		if next.String() != tc.next {
+			t.Errorf("test case %q: expected %s, got %s", tc.name, tc.next, next.String())
+		}
+	}
+}
+
 func TestSortIPs(t *testing.T) {
 	ip1 := oneAddressCIDR(net.ParseIP("10.0.0.1"))
 	ip2 := oneAddressCIDR(net.ParseIP("10.0.0.2"))

pkg/mesh/mesh_test.go

@@ -20,60 +20,6 @@ import (
 	"time"
 )
 
-func TestNewAllocator(t *testing.T) {
-	_, c1, err := net.ParseCIDR("10.1.0.0/16")
-	if err != nil {
-		t.Fatalf("failed to parse CIDR: %v", err)
-	}
-	a1 := newAllocator(*c1)
-	_, c2, err := net.ParseCIDR("10.1.0.0/32")
-	if err != nil {
-		t.Fatalf("failed to parse CIDR: %v", err)
-	}
-	a2 := newAllocator(*c2)
-	_, c3, err := net.ParseCIDR("10.1.0.0/31")
-	if err != nil {
-		t.Fatalf("failed to parse CIDR: %v", err)
-	}
-	a3 := newAllocator(*c3)
-	for _, tc := range []struct {
-		name string
-		a    *allocator
-		next string
-	}{
-		{
-			name: "10.1.0.0/16 first",
-			a:    a1,
-			next: "10.1.0.1/32",
-		},
-		{
-			name: "10.1.0.0/16 second",
-			a:    a1,
-			next: "10.1.0.2/32",
-		},
-		{
-			name: "10.1.0.0/32",
-			a:    a2,
-			next: "<nil>",
-		},
-		{
-			name: "10.1.0.0/31 first",
-			a:    a3,
-			next: "10.1.0.1/32",
-		},
-		{
-			name: "10.1.0.0/31 second",
-			a:    a3,
-			next: "<nil>",
-		},
-	} {
-		next := tc.a.next()
-		if next.String() != tc.next {
-			t.Errorf("test case %q: expected %s, got %s", tc.name, tc.next, next.String())
-		}
-	}
-}
-
 func TestReady(t *testing.T) {
 	internalIP := oneAddressCIDR(net.ParseIP("1.1.1.1"))
 	externalIP := oneAddressCIDR(net.ParseIP("2.2.2.2"))

pkg/mesh/topology.go

@@ -154,7 +154,7 @@ func NewTopology(nodes map[string]*Node, peers map[string]*Peer, granularity Gra
 			return nil, errors.New("failed to allocate an IP address; ran out of IP addresses")
 		}
 		segment.wireGuardIP = ipNet.IP
-		segment.allowedIPs = append(segment.allowedIPs, ipNet)
+		segment.allowedIPs = append(segment.allowedIPs, oneAddressCIDR(ipNet.IP))
 		if t.leader && segment.location == t.location {
 			t.wireGuardCIDR = &net.IPNet{IP: ipNet.IP, Mask: t.subnet.Mask}
 		}