[DONOTMERGE] networking: Add IPNetDeepCopy function

networking/libsnnet/dnsmasq.go

@@ -270,8 +270,8 @@ func (d *Dnsmasq) getSubnetConfiguration() error {
 		return fmt.Errorf("invalid subnet")
 	}
 
-	d.gateway.IP = d.TenantNet.IP.To4().Mask(d.TenantNet.Mask)
-	d.gateway.Mask = d.TenantNet.Mask
+	tenantNetCopy := IPNetDeepCopy(d.TenantNet)
+	d.gateway = *tenantNetCopy
 	d.startIP = d.TenantNet.IP.To4().Mask(d.TenantNet.Mask)
 	d.endIP = d.TenantNet.IP.To4().Mask(d.TenantNet.Mask)
 	//End Hack

networking/libsnnet/utils.go

@@ -68,6 +68,21 @@ func init() {
 	ifaceRsrc = rand.New(ifaceRseed)
 }
 
+// IPNetDeepCopy returns a full copy of a net.IPNet struct
+func IPNetDeepCopy(IPNetToCopy net.IPNet) *net.IPNet {
+	var newIPNet net.IPNet
+
+	// create a copy of the net.IP slice
+	newIPNet.IP = make(net.IP, len(IPNetToCopy.IP))
+	copy(newIPNet.IP, IPNetToCopy.IP)
+
+	// create a copy of the net.IPMask slice
+	newIPNet.Mask = make(net.IPMask, len(IPNetToCopy.Mask))
+	copy(newIPNet.Mask, IPNetToCopy.Mask)
+
+	return &newIPNet
+}
+
 func validSnPrefix(s string) bool {
 	switch {
 	case strings.HasPrefix(s, prefixBridge):

networking/libsnnet/utils_test.go

@@ -17,9 +17,15 @@
 package libsnnet
 
 import (
+	"net"
 	"testing"
 )
 
+const (
+	testCIDRIPv4 = "198.51.100.0/24"
+	testCIDRIPv6 = "2001:db8::/32"
+)
+
 func TestEqualNetSlice(t *testing.T) {
 	netSlice1 := []string{"192.168.0.0/24", "192.168.5.0/24", "192.168.42.0/24"}
 	netSlice2 := []string{"192.168.0.0/24", "192.168.5.0/24", "192.168.42.0/24"}
@@ -29,3 +35,43 @@ func TestEqualNetSlice(t *testing.T) {
 		t.Fatalf("Expected true, got %v", equalSlices)
 	}
 }
+
+// TestIPNetDeepCopyIPv4 tests that given an *IPNet (ip1)
+// creates a full copy of that struct (ip2), so if we
+// modify the copy, original struct should not change
+// this test is expected to pass
+func TestIPNetDeepCopyIPv4(t *testing.T) {
+	_, ip1, _ := net.ParseCIDR(testCIDRIPv4)
+	ip2 := IPNetDeepCopy(*ip1)
+
+	// check address of structs are different
+	if ip1 == ip2 {
+		t.Fatalf("expected a copy of %v, got a reference", ip1)
+	}
+
+	// change values of copy to verify original is not changed
+	ip2.IP = []byte{42, 42, 42, 42}
+	if ip1.String() != testCIDRIPv4 {
+		t.Fatalf("expected %v, got %v", testCIDRIPv4, ip1.String())
+	}
+}
+
+// TestIPNetDeepCopyIPv6 perform a test similar to
+// TestIPNetDeepCopyIPv4 but using an IPv6 CIDR as input
+// this test is expected to pass
+func TestIPNetDeepCopyIPv6(t *testing.T) {
+	_, ip1, _ := net.ParseCIDR(testCIDRIPv6)
+	ip2 := IPNetDeepCopy(*ip1)
+
+	// check address of structs are different
+	if ip1 == ip2 {
+		t.Fatalf("expected a copy of %v, got a reference", ip1)
+	}
+
+	// change values of copy to verify original is not changed
+	// new value "2001:db8:2001:db8:2001:db8:2001:db8"
+	ip2.IP = []byte{32, 01, 13, 184, 32, 01, 13, 184, 32, 01, 13, 184, 32, 01, 13, 184}
+	if ip1.String() != testCIDRIPv6 {
+		t.Fatalf("expected %v, got %v", testCIDRIPv6, ip1.String())
+	}
+}