Fix crash on ListPathRequest with malformed prefix

When ListPathRequest is done by a gRPC client including a malformed prefix,
 the server would crash an invalid memory address reference.

This commit avoid the crash by checking whether the parseCIDR method returned
an error.

pkg/packet/bgp/bgp.go

@@ -9582,7 +9582,15 @@ func NewPrefixFromRouteFamily(afi uint16, safi uint8, prefixStr ...string) (pref
 	family := AfiSafiToRouteFamily(afi, safi)
 
 	f := func(s string) AddrPrefixInterface {
-		addr, net, _ := net.ParseCIDR(s)
+		addr, net, err := net.ParseCIDR(s)
+		if err != nil {
+			fmt.Printf("Invalid CIDR: %v", s)
+			switch family {
+			case RF_IPv4_UC, RF_IPv4_MC:
+				return NewIPAddrPrefix(0, "")
+			}
+			return NewIPv6AddrPrefix(0, "")
+		}
 		len, _ := net.Mask.Size()
 		switch family {
 		case RF_IPv4_UC, RF_IPv4_MC:

pkg/packet/bgp/bgp_test.go

@@ -88,6 +88,25 @@ func Test_IPAddrPrefixString(t *testing.T) {
 	assert.Equal(t, "3343:faba:3903:128::/63", ipv6.String())
 }
 
+func Test_MalformedPrefixLookup(t *testing.T) {
+	assert := assert.New(t)
+	afi, safi := RouteFamilyToAfiSafi(RF_IPv4_UC)
+	prefix, err := NewPrefixFromRouteFamily(afi, safi, "129.6.128/22")
+	assert.Equal(nil, err)
+	assert.Equal("0.0.0.0/0", prefix.String())
+	prefix, err = NewPrefixFromRouteFamily(afi, safi, "foo")
+	assert.Equal(nil, err)
+	assert.Equal("0.0.0.0/0", prefix.String())
+
+	afi, safi = RouteFamilyToAfiSafi(RF_IPv6_UC)
+	prefix, err = NewPrefixFromRouteFamily(afi, safi, "3343:faba:3903:128::::/63")
+	assert.Equal(nil, err)
+	assert.Equal("::/0", prefix.String())
+	prefix, err = NewPrefixFromRouteFamily(afi, safi, "foo")
+	assert.Equal(nil, err)
+	assert.Equal("::/0", prefix.String())
+}
+
 func Test_IPAddrDecode(t *testing.T) {
 	r := IPAddrPrefixDefault{}
 	b := make([]byte, 16)