net/arp: limit arp request when arp is in progress to prevent ARP flooding

Wait a fixed number of milliseconds before sending a retry ARP request for the same destination if the IP address mapping is not exist to prevent ARP flooding

Signed-off-by: wenquan1 <wenquan1@xiaomi.com>

net/arp/Kconfig

@@ -28,6 +28,14 @@ config NET_ARP_MAXAGE
 		The maximum age of ARP table entries measured in deciseconds.  The
 		default value of 120 corresponds to 20 minutes (BSD default).
 
+config NET_ARP_MAXAGE_UNREACHABLE
+	int "Max unreachable ARP entry age"
+	default 1
+	---help---
+		The maximum age of unreachable ARP table entries measured in
+		deciseconds. During unreachable period not send a retry ARP
+		request for the same destination.
+
 config NET_ARP_IPIN
 	bool "ARP address harvesting"
 	default n

net/arp/arp_out.c

@@ -262,6 +262,23 @@ void arp_out(FAR struct net_driver_s *dev)
 
       ninfo("ARP request for IP %08lx\n", (unsigned long)ipaddr);
 
+      if (ret == -EINPROGRESS)
+        {
+          /* The destination address was not in our ARP table, and
+           * the last arp request is in progress, directly drop the packet
+           * to prevent arp flood.
+           */
+
+          dev->d_len = 0;
+          return;
+        }
+
+      /* MAC address marked with all zeros to limit concurrent task
+       * send ARP request for same destination.
+       */
+
+      arp_update(dev, ipaddr, NULL);
+
       /* The destination address was not in our ARP table, so we overwrite
        * the IP packet with an ARP request.
        */

net/arp/arp_send.c

@@ -180,6 +180,7 @@ int arp_send(in_addr_t ipaddr)
   FAR struct net_driver_s *dev;
   struct arp_notify_s notify;
   struct arp_send_s state;
+  bool sending = false;
   int ret;
 
   /* First check if destination is a local broadcast. */
@@ -306,12 +307,12 @@ int arp_send(in_addr_t ipaddr)
        */
 
       netdev_lock(dev);
-      if (arp_find(ipaddr, NULL, dev, true) >= 0)
+      ret = arp_find(ipaddr, NULL, dev, true);
+      if (ret >= 0 || ret == -ENETUNREACH)
         {
-          /* We have it!  Break out with success */
+          /* We have it! Break out with ret value */
 
           netdev_unlock(dev);
-          ret = OK;
           break;
         }
 
@@ -319,6 +320,15 @@ int arp_send(in_addr_t ipaddr)
 
       arp_wait_setup(ipaddr, &notify);
 
+      if (ret == -EINPROGRESS && !sending)
+        {
+          /* ARP request for the same destination is in progress, directly
+           * wait arp response notify.
+           */
+
+          goto wait;
+        }
+
       /* Allocate resources to receive a callback.  This and the following
        * initialization is performed with the network lock because we don't
        * want anything to happen until we are ready.
@@ -351,6 +361,16 @@ int arp_send(in_addr_t ipaddr)
 
       netdev_txnotify_dev(dev);
 
+      /* MAC address marked with all zeros to limit concurrent task
+       * send ARP request for same destination.
+       */
+
+      if (state.snd_retries == 0)
+        {
+          arp_update(dev, ipaddr, NULL);
+          sending = true;
+        }
+
       /* Wait for the send to complete or an error to occur.
        * net_sem_wait will also terminate if a signal is received.
        */
@@ -381,6 +401,7 @@ int arp_send(in_addr_t ipaddr)
 
       /* Now wait for response to the ARP response to be received. */
 
+wait:
       ret = arp_wait(&notify, CONFIG_ARP_SEND_DELAYMSEC);
 
       /* arp_wait will return OK if and only if the matching ARP response
@@ -406,7 +427,6 @@ timeout:
 
   nxsem_destroy(&state.snd_sem);
   arp_callback_free(dev, state.snd_cb);
-
   return ret;
 }
 

net/arp/arp_table.c

@@ -72,6 +72,8 @@
  ****************************************************************************/
 
 #define ARP_MAXAGE_TICK SEC2TICK(10 * CONFIG_NET_ARP_MAXAGE)
+#define ARP_MAXAGE_UNREACHABLE_TICK SEC2TICK(10 * CONFIG_NET_ARP_MAXAGE_UNREACHABLE)
+#define ARP_INPROGRESS_TICK MSEC2TICK(CONFIG_ARP_SEND_MAXTRIES * CONFIG_ARP_SEND_DELAYMSEC)
 
 /****************************************************************************
  * Private Types
@@ -91,6 +93,13 @@ struct arp_table_info_s
 
 static struct arp_entry_s g_arptable[CONFIG_NET_ARPTAB_SIZE];
 
+static const struct ether_addr g_zero_ethaddr =
+{
+  {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+  }
+};
+
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
@@ -322,6 +331,11 @@ int arp_update(FAR struct net_driver_s *dev, in_addr_t ipaddr,
         }
     }
 
+  if (ethaddr == NULL)
+    {
+      ethaddr = g_zero_ethaddr.ether_addr_octet;
+    }
+
   /* When overwrite old entry, notify old entry RTM_DELNEIGH */
 
 #ifdef CONFIG_NETLINK_ROUTE
@@ -422,6 +436,29 @@ int arp_find(in_addr_t ipaddr, FAR uint8_t *ethaddr,
   tabptr = arp_lookup(ipaddr, dev, check_expiry);
   if (tabptr != NULL)
     {
+      /* Addresses that have failed to be searched will return a special
+       * error code so that the upper layer can return faster.
+       */
+
+      if (memcmp(&tabptr->at_ethaddr, &g_zero_ethaddr,
+                 sizeof(tabptr->at_ethaddr)) == 0)
+        {
+          clock_t elapsed;
+          elapsed = clock_systime_ticks() - tabptr->at_time;
+          if (elapsed <= ARP_INPROGRESS_TICK)
+            {
+              return -EINPROGRESS;
+            }
+          else if (elapsed <= ARP_MAXAGE_UNREACHABLE_TICK)
+            {
+              return -ENETUNREACH;
+            }
+          else
+            {
+              return -ENOENT;
+            }
+        }
+
       /* Yes.. return the Ethernet MAC address if the caller has provided a
        * non-NULL address in 'ethaddr'.
        */
@@ -431,8 +468,8 @@ int arp_find(in_addr_t ipaddr, FAR uint8_t *ethaddr,
           memcpy(ethaddr, &tabptr->at_ethaddr, ETHER_ADDR_LEN);
         }
 
-      /* Return success in any case meaning that a valid Ethernet MAC
+      /* Return success meaning that a valid Ethernet MAC address mapping
-       * address mapping is available for the IP address.
+       * is available for the IP address.
        */
 
       return OK;