Fixed bug #28183 (ARP and TCP/IP cannot be disabled on netif used for PPPoE) by adding a new netif flag (NETIF_FLAG_ETHERNET) that tells the stack the device is an ethernet device but prevents usage of ARP (so that ethernet_input can be used for PPPoE).

CHANGELOG

@@ -131,6 +131,13 @@ HISTORY
 
   ++ Bugfixes:
 
+  2010-02-14: Simon Goldschmidt
+  * netif.h, etharp.c, tcpip.c: Fixed bug #28183 (ARP and TCP/IP cannot be
+    disabled on netif used for PPPoE) by adding a new netif flag
+    (NETIF_FLAG_ETHERNET) that tells the stack the device is an ethernet
+    device but prevents usage of ARP (so that ethernet_input can be used
+    for PPPoE).
+
   2010-02-12: Simon Goldschmidt
   * netif.c: netif_set_link_up/down: only do something if the link state
     actually changes

src/api/tcpip.c

@@ -97,7 +97,7 @@ tcpip_thread(void *arg)
     case TCPIP_MSG_INPKT:
       LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip_thread: PACKET %p\n", (void *)msg));
 #if LWIP_ETHERNET
-      if (msg->msg.inp.netif->flags & NETIF_FLAG_ETHARP) {
+      if (msg->msg.inp.netif->flags & (NETIF_FLAG_ETHARP | NETIF_FLAG_ETHERNET)) {
         ethernet_input(msg->msg.inp.p, msg->msg.inp.netif);
       } else
 #endif /* LWIP_ETHERNET */
@@ -140,7 +140,8 @@ tcpip_thread(void *arg)
  * Pass a received packet to tcpip_thread for input processing
  *
  * @param p the received packet, p->payload pointing to the Ethernet header or
- *          to an IP header (if netif doesn't got NETIF_FLAG_ETHARP flag)
+ *          to an IP header (if inp doesn't have NETIF_FLAG_ETHARP or
+ *          NETIF_FLAG_ETHERNET flags)
  * @param inp the network interface on which the packet was received
  */
 err_t

src/include/lwip/netif.h

@@ -87,9 +87,13 @@ extern "C" {
  * Set by the netif driver in its init function.
  * Used to check input packet types and use of DHCP. */
 #define NETIF_FLAG_ETHARP       0x20U
+/** If set, the netif is an ethernet device. It might not use
+ * ARP or TCP/IP if it is used for PPPoE only.
+ */
+#define NETIF_FLAG_ETHERNET     0x40U
 /** If set, the netif has IGMP capability.
  * Set by the netif driver in its init function. */
-#define NETIF_FLAG_IGMP         0x40U
+#define NETIF_FLAG_IGMP         0x80U
 
 /** Function prototype for netif init functions. Set up flags and output/linkoutput
  * callback functions in this function.

src/netif/etharp.c

@@ -586,6 +586,7 @@ etharp_ip_input(struct netif *netif, struct pbuf *p)
   struct eth_hdr *ethhdr;
   struct ip_hdr *iphdr;
   LWIP_ERROR("netif != NULL", (netif != NULL), return;);
+
   /* Only insert an entry if the source IP address of the
      incoming IP packet comes from a host on the local network. */
   ethhdr = (struct eth_hdr *)p->payload;
@@ -639,7 +640,7 @@ etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr, struct pbuf *p)
 #endif /* LWIP_AUTOIP */
 
   LWIP_ERROR("netif != NULL", (netif != NULL), return;);
-  
+
   /* drop short ARP packets: we have to check for p->len instead of p->tot_len here
      since a struct etharp_hdr is pointed to p->payload, so it musn't be chained! */
   if (p->len < SIZEOF_ETHARP_PACKET) {
@@ -1185,6 +1186,9 @@ ethernet_input(struct pbuf *p, struct netif *netif)
 #if LWIP_ARP
     /* IP packet? */
     case ETHTYPE_IP:
+      if (!(netif->flags & NETIF_FLAG_ETHARP)) {
+        goto free_and_return;
+      }
 #if ETHARP_TRUST_IP_MAC
       /* update ARP table */
       etharp_ip_input(netif, p);
@@ -1192,8 +1196,7 @@ ethernet_input(struct pbuf *p, struct netif *netif)
       /* skip Ethernet header */
       if(pbuf_header(p, -(s16_t)SIZEOF_ETH_HDR)) {
         LWIP_ASSERT("Can't move over header in packet", 0);
-        pbuf_free(p);
+        goto free_and_return;
-        p = NULL;
       } else {
         /* pass to IP layer */
         ip_input(p, netif);
@@ -1201,6 +1204,9 @@ ethernet_input(struct pbuf *p, struct netif *netif)
       break;
       
     case ETHTYPE_ARP:
+      if (!(netif->flags & NETIF_FLAG_ETHARP)) {
+        goto free_and_return;
+      }
       /* pass p to ARP module */
       etharp_arp_input(netif, (struct eth_addr*)(netif->hwaddr), p);
       break;
@@ -1218,13 +1224,15 @@ ethernet_input(struct pbuf *p, struct netif *netif)
     default:
       ETHARP_STATS_INC(etharp.proterr);
       ETHARP_STATS_INC(etharp.drop);
-      pbuf_free(p);
+      goto free_and_return;
-      p = NULL;
-      break;
   }
 
   /* This means the pbuf is freed or consumed,
      so the caller doesn't have to free it again */
   return ERR_OK;
+
+free_and_return:
+  pbuf_free(p);
+  return ERR_OK;
 }
 #endif /* LWIP_ARP || LWIP_ETHERNET */