func setupIpMasq(localNet ip.IP4Net, overlayNet ip.IP4Net) error { ipt, err := ip.NewIPTables() if err != nil { return err } err = ipt.ClearChain("nat", "FLANNEL") if err != nil { return fmt.Errorf("Failed to create/clear FLANNEL chain in NAT table: %v", err) } rules := [][]string{ {"FLANNEL", "-s", localNet.String(), "-o", "lo", "-j", "ACCEPT"}, {"FLANNEL", "-s", localNet.String(), "!", "-d", overlayNet.String(), "-j", "MASQUERADE"}, {"POSTROUTING", "-s", localNet.String(), "-j", "FLANNEL"}, } for _, args := range rules { log.Info("Adding iptables rule: ", strings.Join(args, " ")) if err := ipt.AppendUnique("nat", args...); err != nil { return fmt.Errorf("Failed to insert IP masquerade rule: %v", err) } } return nil }