[lwIP] Modify the ip.c to support NAT

components/net/lwip-1.4.1/src/core/ipv4/ip.c

@@ -312,6 +312,11 @@ ip_input(struct pbuf *p, struct netif *inp)
   int check_ip_src=1;
 #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
 
+#if IP_NAT
+  extern u8_t ip_nat_input(struct pbuf *p);
+  extern u8_t ip_nat_out(struct pbuf *p);
+#endif
+
   IP_STATS_INC(ip.recv);
   snmp_inc_ipinreceives();
 
@@ -487,15 +492,30 @@ ip_input(struct pbuf *p, struct netif *inp)
 
   /* packet not for us? */
   if (netif == NULL) {
+#if IP_FORWARD || IP_NAT
+    u8_t taken = 0;
+#endif /* IP_FORWARD || IP_NAT */
     /* packet not for us, route or discard */
     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: packet not for us.\n"));
-#if IP_FORWARD
+#if IP_FORWARD || IP_NAT
     /* non-broadcast packet? */
-    if (!ip_addr_isbroadcast(&current_iphdr_dest, inp)) {
-      /* try to forward IP packet on (other) interfaces */
-      ip_forward(p, iphdr, inp);
-    } else
+    if (!ip_addr_isbroadcast(&(iphdr->dest), inp)) {
+#if IP_NAT
+      /* check if we want to perform NAT with this packet. */
+      taken = ip_nat_out(p);
+      if (!taken)
+#endif /* IP_NAT */
+      {
+#if IP_FORWARD
+        /* try to forward IP packet on (other) interfaces */
+        if (ip_forward(p, iphdr, inp) != NULL) {
+          taken = 1;
+        }
 #endif /* IP_FORWARD */
+      }
+    }
+    if (!taken)
+#endif /* IP_FORWARD || IP_NAT */
     {
       snmp_inc_ipinaddrerrors();
       snmp_inc_ipindiscards();
@@ -553,6 +573,13 @@ ip_input(struct pbuf *p, struct netif *inp)
   current_netif = inp;
   current_header = iphdr;
 
+#if IP_NAT
+  if (!ip_addr_isbroadcast(&(iphdr->dest), inp) &&
+      (ip_nat_input(p) != 0)) {
+     LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet consumed by nat layer\n"));
+  } else
+#endif /* IP_NAT */
+
 #if LWIP_RAW
   /* raw input did not eat the packet? */
   if (raw_input(p, inp) == 0)

components/net/lwip_nat/ipv4_nat.c

@@ -434,8 +434,8 @@ ip_nat_check_header(struct pbuf *p, u16_t min_size)
  * @return 1 if the packet has been consumed (it was a NAT packet),
  *         0 if the packet has not been consumed (no NAT packet)
  */
-int 
-ip_nat_input(struct pbuf *p, struct netif *inp)
+u8_t  
+ip_nat_input(struct pbuf *p)
 {
   struct ip_hdr        *iphdr = (struct ip_hdr*)p->payload;
   struct tcp_hdr       *tcphdr;
@@ -443,7 +443,7 @@ ip_nat_input(struct pbuf *p, struct netif *inp)
   struct icmp_echo_hdr *icmphdr;
   nat_entry_t           nat_entry;
   err_t                 err;
-  int                   consumed = 0;
+  u8_t                  consumed = 0;
   int                   i;
   struct pbuf          *q = NULL;
 

components/net/lwip_nat/ipv4_nat.h

@@ -88,7 +88,7 @@ typedef struct ip_nat_entry
 
 void  ip_nat_init(void);
 void  ip_nat_tmr(void);
-int   ip_nat_input(struct pbuf *p, struct netif *inp);
+u8_t  ip_nat_input(struct pbuf *p);
 u8_t  ip_nat_out(struct pbuf *p);
 
 err_t ip_nat_add(const ip_nat_entry_t *new_entry);