task #7506: added NAT support

CHANGELOG

@@ -13,6 +13,9 @@ HISTORY
 
   ++ New features:
 
+  2010-05-05: Simon Goldschmidt (Christian Walter)
+  * ip_nat.h/.c, opt.h, ip.c, timers.c: task #7506: added NAT support
+
   2010-05-02: Simon Goldschmidt
   * netbuf.h/.c, sockets.c, api_msg.c: use checksum-on-copy for sending
     UDP data for LWIP_NETIF_TX_SINGLE_PBUF==1

src/core/ipv4/ip.c

@@ -43,6 +43,7 @@
 #include "lwip/def.h"
 #include "lwip/mem.h"
 #include "lwip/ip_frag.h"
+#include "lwip/ip_nat.h"
 #include "lwip/inet_chksum.h"
 #include "lwip/netif.h"
 #include "lwip/icmp.h"
@@ -377,15 +378,30 @@ 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(&(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 */
-      ip_forward(p, iphdr, inp);
+        if (ip_forward(p, iphdr, inp) != NULL) {
-    } else
+          taken = 1;
+        }
 #endif /* IP_FORWARD */
+      }
+    }
+    if (!taken)
+#endif /* IP_FORWARD || IP_NAT */
     {
       snmp_inc_ipinaddrerrors();
       snmp_inc_ipindiscards();
@@ -443,6 +459,12 @@ 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)

src/core/timers.c

@@ -53,6 +53,7 @@
 #include "lwip/autoip.h"
 #include "lwip/igmp.h"
 #include "lwip/dns.h"
+#include "lwip/ip_nat.h"
 
 
 /** The one and only timeout list */
@@ -214,6 +215,22 @@ dns_timer(void *arg)
 }
 #endif /* LWIP_DNS */
 
+#if IP_NAT
+/**
+ * Timer callback function that calls ip_nat_tmr() and reschedules itself.
+ *
+ * @param arg unused argument
+ */
+static void
+nat_timer(void *arg)
+{
+  LWIP_UNUSED_ARG(arg);
+  LWIP_DEBUGF(TIMERS_DEBUG, ("tcpip: nat_timer()\n"));
+  ip_nat_tmr();
+  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC, nat_timer, NULL);
+}
+#endif /* IP_NAT */
+
 /** Initialize this module */
 void sys_timeouts_init(void)
 {
@@ -236,6 +253,9 @@ void sys_timeouts_init(void)
 #if LWIP_DNS
   sys_timeout(DNS_TMR_INTERVAL, dns_timer, NULL);
 #endif /* LWIP_DNS */
+#if IP_NAT
+  sys_timeout(LWIP_NAT_TMR_INTERVAL_SEC, nat_timer, NULL);
+#endif /* IP_NAT */
 
 #if NO_SYS
   /* Initialise timestamp for sys_check_timeouts */

src/include/ipv4/lwip/ip_nat.h

@@ -0,0 +1,51 @@
+/***************************************************************************
+ * Template - A brief description for this module.
+ * Copyright (c) 2008 Christian Walter, © Embedded Solutions, Vienna 2006.
+ *
+ * $Id: ip_nat.h,v 1.1 2010/05/05 19:34:23 goldsimon Exp $
+ ***************************************************************************/
+
+#ifndef __LWIP_NAT_H__
+#define __LWIP_NAT_H__
+
+#include "lwip/err.h"
+#include "lwip/ip_addr.h"
+#include "lwip/opt.h"
+
+#if IP_NAT
+
+/** Timer interval at which to call ip_nat_tmr() */
+#define LWIP_NAT_TMR_INTERVAL_SEC        5
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+struct netif;
+struct pbuf;
+
+typedef struct ip_nat_entry
+{
+  ip_addr_t    source_net;
+  ip_addr_t    source_netmask;
+  ip_addr_t    dest_net;
+  ip_addr_t    dest_netmask;
+  struct netif *out_if;
+  struct netif *in_if;
+} ip_nat_entry_t;
+
+void  ip_nat_init(void);
+void  ip_nat_tmr(void);
+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);
+void  ip_nat_remove(const ip_nat_entry_t *remove_entry);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* IP_NAT */
+
+#endif /* __LWIP_NAT_H__ */

src/include/lwip/opt.h

@@ -466,6 +466,11 @@
 #define IP_FORWARD                      0
 #endif
 
+/** IP_NAT==1: Enables network address translation code */
+#ifndef IP_NAT
+#define IP_NAT                          0
+#endif
+
 /**
  * IP_OPTIONS_ALLOWED: Defines the behavior for IP options.
  *      IP_OPTIONS_ALLOWED==0: All packets with IP options are dropped.