First version of nat enabling

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>

docs/usb_moded-doc.txt

@@ -143,8 +143,9 @@ on the device to route traffic coming from your pc/laptop. The best use case exa
 to the internet over USB using the data connection of your smartphone.
 
 To enable this you need to add the following lines to your network config (the example expects rmnet0 to be
-your internet facing interface). When a nat_interface is defined it will be enabled.
+your internet facing interface). When a nat is set to 1 it will set up the forwarding.
 
+nat = 1
 nat_interface = rmnet0
 
 

src/usb_moded-config.c

@@ -143,6 +143,11 @@ const char * get_network_gateway(void)
   return(get_conf_string(NETWORK_ENTRY, NETWORK_GATEWAY_KEY));
 }
 
+int get_network_nat(void)
+{
+  return(get_conf_int(NETWORK_ENTRY, NETWORK_NAT_KEY));
+}
+
 const char * get_network_nat_interface(void)
 {
   return(get_conf_string(NETWORK_ENTRY, NETWORK_NAT_INTERFACE_KEY));

src/usb_moded-config.h

@@ -48,6 +48,7 @@
 #define NETWORK_IP_KEY			"ip"
 #define NETWORK_INTERFACE_KEY		"interface"
 #define NETWORK_GATEWAY_KEY		"gateway"
+#define NETWORK_NAT_KEY			"nat"
 #define NETWORK_NAT_INTERFACE_KEY	"nat_interface"
 #define ANDROID_ENTRY			"android"
 #define ANDROID_MANUFACTURER_KEY	"iManufacturer"
@@ -81,6 +82,7 @@ const char * get_network_ip(void);
 const char * get_network_interface(void);
 const char * get_network_gateway(void);
 const char * get_network_nat_interface(void);
+int get_network_nat(void);
 
 const char * get_android_manufacturer(void);
 const char * get_android_vendor_id(void);

src/usb_moded-network.c

@@ -34,6 +34,7 @@
 #include "usb_moded-network.h"
 #include "usb_moded-config.h"
 #include "usb_moded-log.h"
+#include "usb_moded-modesetting.h"
 
 #if CONNMAN
 #include <dbus/dbus.h>
@@ -67,6 +68,31 @@ static char* get_interface(struct mode_list_elem *data)
   return interface;
 }
 
+/**
+ * Turn on ip forwarding on the usb interface
+ */
+static void set_usb_ip_forward(struct mode_list_elem *data)
+{
+  const char *interface, *nat_interface;
+  char command[128];
+
+  interface = get_interface(data);
+  nat_interface = get_network_nat_interface();
+
+  write_to_file("/proc/sys/net/ipv4/ip_forward", "1");
+  snprintf(command, 128, "/sbin/iptables -t nat -A POSTROUTING -o %s -j MASQUERADE", nat_interface);
+  system(command);
+
+  snprintf(command, 128, "/sbin/iptables -A FORWARD -i %s -o %s  -m state  --state RELATED,ESTABLISHED -j ACCEPT", nat_interface, interface);
+  system(command);
+
+  snprintf(command, 128, "/sbin/iptables -A FORWARD -i %s -o %s -j ACCEPT", interface, nat_interface);
+  system(command);
+
+  free((char *)interface);
+  free((char *)nat_interface);
+}
+
 /**
  * Activate the network interface
  *
@@ -132,6 +158,9 @@ int usb_network_up(struct mode_list_elem *data)
         system(command);
   }
 
+  if(get_network_nat())
+	set_usb_ip_forward(data);
+
 clean:
   free((char *)interface);
   free((char *)gateway);