Libcalico-go: Prevent segfault when network/ip is not valid

Author: bartekzurawski

libcalico-go/lib/backend/model/rule.go

@@ -130,7 +130,9 @@ func (r Rule) AllNotDstNets() []*net.IPNet {
 func joinNets(nets []*net.IPNet) string {
 	parts := make([]string, len(nets))
 	for i, n := range nets {
-		parts[i] = n.String()
+		if n != nil {
+			parts[i] = n.String()
+		}
 	}
 	return strings.Join(parts, ",")
 }

libcalico-go/lib/backend/syncersv1/updateprocessors/rules.go

@@ -278,7 +278,9 @@ func NormalizeIPNets(nets []string) []*cnet.IPNet {
 	}
 	out := make([]*cnet.IPNet, len(nets))
 	for i, n := range nets {
-		out[i] = normalizeIPNet(n)
+		if x := normalizeIPNet(n); x != nil {
+			out[i] = x
+		}
 	}
 	return out
 }