Make USB network settings configurable

config.go

@@ -96,6 +96,7 @@ type Config struct {
 	UsbConfig            *usbgadget.Config         `json:"usb_config"`
 	UsbDevices           *usbgadget.Devices        `json:"usb_devices"`
 	NetworkConfig        *network.NetworkConfig    `json:"network_config"`
+	UsbNetworkConfig     *network.UsbNetworkConfig `json:"usb_network_config"`
 	DefaultLogLevel      string                    `json:"default_log_level"`
 }
 
@@ -128,7 +129,13 @@ var defaultConfig = &Config{
 		EthernetNcm:   false,
 		EthernetRndis: false,
 	},
-	NetworkConfig:   &network.NetworkConfig{},
+	NetworkConfig: &network.NetworkConfig{
+		NatEnable: false,
+	},
+	UsbNetworkConfig: &network.UsbNetworkConfig{
+		IPv4Addr:    "172.16.55.1",
+		IPv4Network: "172.16.55.0/24",
+	},
 	DefaultLogLevel: "INFO",
 }
 

internal/network/config.go

@@ -48,6 +48,13 @@ type NetworkConfig struct {
 	TimeSyncOrdering        []string    `json:"time_sync_ordering,omitempty" one_of:"http,ntp,ntp_dhcp,ntp_user_provided,ntp_fallback" default:"ntp,http"`
 	TimeSyncDisableFallback null.Bool   `json:"time_sync_disable_fallback,omitempty" default:"false"`
 	TimeSyncParallel        null.Int    `json:"time_sync_parallel,omitempty" default:"4"`
+
+	NatEnable bool `json:"nat_enable,omitempty" default:"false" required:"true"`
+}
+
+type UsbNetworkConfig struct {
+	IPv4Addr    string `json:"ipv4_addr,omitempty" validate_type:"ipv4" default:"172.16.55.1" required:"true"`
+	IPv4Network string `json:"ipv4_network,omitempty" validate_type:"ipv4" default:"172.16.55.0/24" required:"true"`
 }
 
 func (c *NetworkConfig) GetMDNSMode() *mdns.MDNSListenOptions {

internal/network/nat.go

@@ -13,13 +13,8 @@ const (
 func (s *NetworkInterfaceState) reconfigureNat(wantNat bool, sourceAddr string) error {
 	scopedLogger := s.l.With().Str("iface", s.interfaceName).Logger()
 
-	if wantNat && s.IsOnline() {
-		scopedLogger.Info().Msg("enabling NAT")
-		err := enableNat(sourceAddr, s.interfaceName, s.IPv4String())
-		if err != nil {
-			s.l.Error().Err(err).Msg("failed to enable NAT")
-		}
-	} else {
+	if !wantNat {
+		if s.natEnabled {
 			scopedLogger.Info().Msg("disabling NAT")
 			err := disableNat()
 			if err != nil {
@@ -29,6 +24,19 @@ func (s *NetworkInterfaceState) reconfigureNat(wantNat bool, sourceAddr string)
 		return nil
 	}
 
+	if wantNat && s.IsOnline() {
+		scopedLogger.Info().Msg("enabling NAT")
+		err := enableNat(sourceAddr, s.interfaceName, s.IPv4String())
+		if err != nil {
+			s.l.Error().Err(err).Msg("failed to enable NAT")
+		}
+		s.natEnabled = true
+		return nil
+	}
+
+	return nil
+}
+
 func enableNat(sourceAddr string, oIfName string, snatToAddr string) error {
 	if err := os.WriteFile(procIpv4ForwardPath, []byte("1"), 0644); err != nil {
 		return fmt.Errorf("failed to write %s: %w", procIpv4ForwardPath, err)

internal/network/netif.go

@@ -37,6 +37,8 @@ type NetworkInterfaceState struct {
 	onInitialCheck func(state *NetworkInterfaceState)
 	cbConfigChange func(config *NetworkConfig)
 
+	natEnabled bool
+
 	checked bool
 }
 
@@ -50,6 +52,7 @@ type NetworkInterfaceOptions struct {
 	OnDhcpLeaseChange func(lease *udhcpc.Lease)
 	OnConfigChange    func(config *NetworkConfig)
 	NetworkConfig     *NetworkConfig
+	UsbNetworkConfig  *UsbNetworkConfig
 }
 
 func NewNetworkInterfaceState(opts *NetworkInterfaceOptions) (*NetworkInterfaceState, error) {
@@ -73,11 +76,11 @@ func NewNetworkInterfaceState(opts *NetworkInterfaceOptions) (*NetworkInterfaceS
 		stateLock:       sync.Mutex{},
 		l:               l,
 		onStateChange: func(s *NetworkInterfaceState) {
-			s.reconfigureNat(true, "172.16.55.0/24")
+			s.reconfigureNat(opts.NetworkConfig.NatEnable, opts.UsbNetworkConfig.IPv4Network)
 			opts.OnStateChange(s)
 		},
 		onInitialCheck: func(s *NetworkInterfaceState) {
-			s.reconfigureNat(true, "172.16.55.0/24")
+			s.reconfigureNat(opts.NetworkConfig.NatEnable, opts.UsbNetworkConfig.IPv4Network)
 			opts.OnInitialCheck(s)
 		},
 		cbConfigChange: opts.OnConfigChange,

network.go

@@ -35,6 +35,7 @@ func initNetwork() error {
 		DefaultHostname:  GetDefaultHostname(),
 		InterfaceName:    NetIfName,
 		NetworkConfig:    config.NetworkConfig,
+		UsbNetworkConfig: config.UsbNetworkConfig,
 		Logger:           networkLogger,
 		OnStateChange: func(state *network.NetworkInterfaceState) {
 			networkStateChanged()