loopif is not required for loopback traffic any more but passed through any netif (ENABLE_LOOPBACK has to be enabled) (task #13515)

CHANGELOG

@@ -6,6 +6,9 @@ HISTORY
 
   ++ New features:
 
+  * opt.h, ip4_addr.h, ip4.c, ip6.c: loopif is not required for loopback traffic
+    any more but passed through any netif (ENABLE_LOOPBACK has to be enabled)
+
   2015-03-23: Simon Goldschmidt
   * opt.h, etharp.c: with ETHARP_TABLE_MATCH_NETIF== 1, duplicate (Auto)-IP
     addresses on multiple netifs should now be working correctly (if correctly

src/core/ipv4/ip4.c

@@ -160,7 +160,28 @@ ip_route(const ip_addr_t *dest)
     snmp_inc_ipoutnoroutes();
     return NULL;
   }
+
+#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
+  /* loopif is disabled, looopback traffic is passed through any netif */
+  if (ip_addr_isloopback(dest)) {
+    /* don't check for link on loopback traffic */
+    if (netif_is_up(netif_default)) {
+      return netif_default;
+    }
+    /* default netif is not up, just use any netif for loopback traffic */
+    for (netif = netif_list; netif != NULL; netif = netif->next) {
+      if (netif_is_up(netif)) {
+        return netif;
+      }
+    }
+    return NULL;
+  }
+#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
+
   /* no matching netif found, use default netif */
+  if (!netif_is_up(netif_default) || !netif_is_link_up(netif_default)) {
+    return NULL;
+  }
   return netif_default;
 }
 
@@ -431,7 +452,11 @@ ip_input(struct pbuf *p, struct netif *inp)
         /* unicast to this interface address? */
         if (ip_addr_cmp(ip_current_dest_addr(), &(netif->ip_addr)) ||
             /* or broadcast on this interface network address? */
-            ip_addr_isbroadcast(ip_current_dest_addr(), netif)) {
+            ip_addr_isbroadcast(ip_current_dest_addr(), netif)
+#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
+            || (ip4_addr_get_u32(ip_current_dest_addr()) == PP_HTONL(IPADDR_LOOPBACK))
+#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
+            ) {
           LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n",
               netif->name[0], netif->name[1]));
           /* break out of for loop */
@@ -841,7 +866,11 @@ err_t ip_output_if_opt_src(struct pbuf *p, const ip_addr_t *src, const ip_addr_t
   ip_debug_print(p);
 
 #if ENABLE_LOOPBACK
-  if (ip_addr_cmp(dest, &netif->ip_addr)) {
+  if (ip_addr_cmp(dest, &netif->ip_addr)
+#if !LWIP_HAVE_LOOPIF
+      || ip_addr_isloopback(dest)
+#endif /* !LWIP_HAVE_LOOPIF */
+      ) {
     /* Packet to self, enqueue it for loopback */
     LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));
     return netif_loop_output(netif, p);

src/core/ipv6/ip6.c

@@ -168,6 +168,23 @@ ip6_route(const struct ip6_addr *src, const struct ip6_addr *dest)
     }
   }
 
+#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
+  /* loopif is disabled, loopback traffic is passed through any netif */
+  if (ip6_addr_isloopback(dest)) {
+    /* don't check for link on loopback traffic */
+    if (netif_is_up(netif_default)) {
+      return netif_default;
+    }
+    /* default netif is not up, just use any netif for loopback traffic */
+    for (netif = netif_list; netif != NULL; netif = netif->next) {
+      if (netif_is_up(netif)) {
+        return netif;
+      }
+    }
+    return NULL;
+  }
+#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
+
   /* no matching netif found, use default netif, if up */
   if (!netif_is_up(netif_default) || !netif_is_link_up(netif_default)) {
     return NULL;
@@ -855,6 +872,11 @@ ip6_output_if_src(struct pbuf *p, const ip6_addr_t *src, const ip6_addr_t *dest,
 #if ENABLE_LOOPBACK
   {
     int i;
+#if !LWIP_HAVE_LOOPIF
+    if (ip6_addr_isloopback(dest)) {
+      return netif_loop_output(netif, p);
+    }
+#endif /* !LWIP_HAVE_LOOPIF */
     for (i = 0; i < LWIP_IPV6_NUM_ADDRESSES; i++) {
       if (ip6_addr_isvalid(netif_ip6_addr_state(netif, i)) &&
           ip6_addr_cmp(dest, netif_ip6_addr(netif, i))) {

src/include/lwip/ip4_addr.h

@@ -170,6 +170,8 @@ extern const ip_addr_t ip_addr_broadcast;
 #define ip_addr_set_any(ipaddr)       ((ipaddr)->addr = IPADDR_ANY)
 /** Set address to loopback address */
 #define ip_addr_set_loopback(ipaddr)  ((ipaddr)->addr = PP_HTONL(IPADDR_LOOPBACK))
+/** Check if an address is in the loopback region */
+#define ip_addr_isloopback(ipaddr)    (((ipaddr)->addr & PP_HTONL(IP_CLASSA_NET)) == PP_HTONL(((u32_t)IP_LOOPBACKNET) << 24))
 /** Safely copy one IP address to another and change byte order
  * from host- to network-order. */
 #define ip_addr_set_hton(dest, src) ((dest)->addr = \

src/include/lwip/opt.h

@@ -1375,7 +1375,9 @@
    ------------------------------------
 */
 /**
- * LWIP_HAVE_LOOPIF==1: Support loop interface (127.0.0.1)
+ * LWIP_HAVE_LOOPIF==1: Support loop interface (127.0.0.1).
+ * This is only needed when no real netifs are available. If at least one other
+ * netif is available, loopback traffic uses this netif.
  */
 #ifndef LWIP_HAVE_LOOPIF
 #define LWIP_HAVE_LOOPIF                0