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@@ -79,12 +79,24 @@ func (s *Server) Run(ctx context.Context) error {
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AuthRequired: true,
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}
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payload, _ := json.Marshal(resp)
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- if _, err := writeToUDP(conn, payload, remote, packetInfo, net.ParseIP(lan2IP)); err != nil {
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- s.log.Warn("failed to send udp discovery response", "remote", remote.String(), "local_ip", lan2IP, "interface_index", packetInfo.ifIndex, "error", err.Error())
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+ responseSourceIP := findResponseSourceIP(packetInfo.ifIndex, remote.IP)
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+ responseTarget := remote
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+ broadcastResponse := false
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+ if responseSourceIP == nil && packetInfo.ifIndex > 0 {
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+ responseSourceIP = net.ParseIP(lan2IP)
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+ responseTarget = broadcastResponseTarget(remote)
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+ broadcastResponse = true
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+ }
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+ if _, err := writeToUDP(conn, payload, responseTarget, packetInfo, responseSourceIP); err != nil {
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+ s.log.Warn("failed to send udp discovery response", "remote", remote.String(), "target", responseTarget.String(), "source_ip", responseSourceIP.String(), "maintenance_ip", lan2IP, "interface_index", packetInfo.ifIndex, "broadcast", broadcastResponse, "error", err.Error())
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}
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}
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}
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+func broadcastResponseTarget(remote *net.UDPAddr) *net.UDPAddr {
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+ return &net.UDPAddr{IP: net.IPv4bcast, Port: remote.Port}
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+}
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+
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type udpPacketInfo struct {
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localIP net.IP
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ifIndex int
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@@ -96,6 +108,7 @@ func (s *Server) maintenanceEndpoint(packetInfo udpPacketInfo) (string, string)
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if lan2IP != "" {
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return lan2IP, mac
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}
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+ return "", ""
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}
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if packetInfo.localIP != nil {
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lan2IP, mac := findLinkLocalEndpointByInterfaceIP(packetInfo.localIP.String())
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@@ -112,6 +125,43 @@ func (s *Server) maintenanceEndpoint(packetInfo udpPacketInfo) (string, string)
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return findFirstLinkLocalEndpoint()
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}
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+func findResponseSourceIP(interfaceIndex int, remoteIP net.IP) net.IP {
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+ if interfaceIndex <= 0 {
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+ return nil
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+ }
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+ iface, err := net.InterfaceByIndex(interfaceIndex)
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+ if err != nil {
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+ return nil
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+ }
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+ addresses, err := iface.Addrs()
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+ if err != nil {
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+ return nil
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+ }
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+ return bestSourceIPForRemote(addresses, remoteIP)
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+}
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+
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+func bestSourceIPForRemote(addresses []net.Addr, remoteIP net.IP) net.IP {
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+ remoteIPv4 := remoteIP.To4()
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+ if remoteIPv4 == nil {
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+ return nil
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+ }
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+ var best net.IP
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+ bestPrefix := -1
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+ for _, address := range addresses {
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+ ipNet, ok := address.(*net.IPNet)
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+ if !ok || ipNet.IP.To4() == nil || !ipNet.Contains(remoteIPv4) {
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+ continue
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+ }
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+ prefix, bits := ipNet.Mask.Size()
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+ if bits != 32 || prefix <= bestPrefix {
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+ continue
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+ }
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+ best = ipNet.IP.To4()
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+ bestPrefix = prefix
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+ }
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+ return best
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+}
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+
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func findLinkLocalEndpointByInterfaceIndex(index int) (string, string) {
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iface, err := net.InterfaceByIndex(index)
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if err != nil {
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