net/arp: reducing unnecessary ARP requests can mitigate

network congestion and avoid packet delays caused by
waiting for ARP responses

Signed-off-by: nuttxs <[email protected]>

Author: nuttxs

net/arp/arp.h

@@ -425,7 +425,7 @@ void arp_notify(in_addr_t ipaddr);
 
 struct ether_addr;  /* Forward reference */
 int arp_find(in_addr_t ipaddr, FAR uint8_t *ethaddr,
-             FAR struct net_driver_s *dev);
+             FAR struct net_driver_s *dev, bool check_expiry);
 
 /****************************************************************************
  * Name: arp_delete
@@ -620,7 +620,7 @@ void arp_acd_setup(FAR struct net_driver_s *dev);
 #  define arp_wait_cancel(n) (0)
 #  define arp_wait(n,t) (0)
 #  define arp_notify(i)
-#  define arp_find(i,e,d) (-ENOSYS)
+#  define arp_find(i,e,d,u) (-ENOSYS)
 #  define arp_delete(i,d) (-ENOSYS)
 #  define arp_cleanup(d)
 #  define arp_update(d,i,m);

net/arp/arp_out.c

@@ -262,7 +262,7 @@ void arp_out(FAR struct net_driver_s *dev)
 
   /* Check if we already have this destination address in the ARP table */
 
-  ret = arp_find(ipaddr, ethaddr.ether_addr_octet, dev);
+  ret = arp_find(ipaddr, ethaddr.ether_addr_octet, dev, false);
   if (ret < 0)
     {
       ninfo("ARP request for IP %08lx\n", (unsigned long)ipaddr);

net/arp/arp_send.c

@@ -314,7 +314,7 @@ int arp_send(in_addr_t ipaddr)
        * issue.
        */
 
-      ret = arp_find(ipaddr, NULL, dev);
+      ret = arp_find(ipaddr, NULL, dev, true);
       if (ret >= 0)
         {
           /* We have it!  Break out with success */

net/arp/arp_table.c

@@ -186,6 +186,7 @@ arp_return_old_entry(FAR struct arp_entry_s *e1, FAR struct arp_entry_s *e2)
  * Input Parameters:
  *   ipaddr - Refers to an IP address in network order
  *   dev    - Device structure
+ *   check_expiry - Expiry check
  *
  * Assumptions:
  *   The network is locked to assure exclusive access to the ARP table.
@@ -194,7 +195,8 @@ arp_return_old_entry(FAR struct arp_entry_s *e1, FAR struct arp_entry_s *e2)
  ****************************************************************************/
 
 static FAR struct arp_entry_s *arp_lookup(in_addr_t ipaddr,
-                                          FAR struct net_driver_s *dev)
+                                          FAR struct net_driver_s *dev,
+                                          bool check_expiry)
 {
   FAR struct arp_entry_s *tabptr;
   int i;
@@ -205,10 +207,23 @@ static FAR struct arp_entry_s *arp_lookup(in_addr_t ipaddr,
     {
       tabptr = &g_arptable[i];
       if (tabptr->at_dev == dev &&
-          net_ipv4addr_cmp(ipaddr, tabptr->at_ipaddr) &&
-          clock_systime_ticks() - tabptr->at_time <= ARP_MAXAGE_TICK)
+          net_ipv4addr_cmp(ipaddr, tabptr->at_ipaddr))
         {
-          return tabptr;
+          /* Find matching entries */
+
+          if (!check_expiry)
+            {
+              return tabptr;  /* Ignore expiration time */
+            }
+
+          /* Check if it has expired */
+
+          if (clock_systime_ticks() - tabptr->at_time <= ARP_MAXAGE_TICK)
+            {
+              return tabptr;
+            }
+
+          return NULL;  /* Expired */
         }
     }
 
@@ -401,21 +416,22 @@ void arp_hdr_update(FAR struct net_driver_s *dev, FAR uint16_t *pipaddr,
  *             used simply to determine if the Ethernet MAC address is
  *             available.
  *   dev     - Device structure
+ *   check_expiry  - Expiry check
  *
  * Assumptions
  *   The network is locked to assure exclusive access to the ARP table.
  *
  ****************************************************************************/
 
 int arp_find(in_addr_t ipaddr, FAR uint8_t *ethaddr,
-             FAR struct net_driver_s *dev)
+             FAR struct net_driver_s *dev, bool check_expiry)
 {
   FAR struct arp_entry_s *tabptr;
   struct arp_table_info_s info;
 
   /* Check if the IPv4 address is already in the ARP table. */
 
-  tabptr = arp_lookup(ipaddr, dev);
+  tabptr = arp_lookup(ipaddr, dev, check_expiry);
   if (tabptr != NULL)
     {
       /* Addresses that have failed to be searched will return a special
@@ -485,7 +501,7 @@ int arp_delete(in_addr_t ipaddr, FAR struct net_driver_s *dev)
 #endif
   /* Check if the IPv4 address is in the ARP table. */
 
-  tabptr = arp_lookup(ipaddr, dev);
+  tabptr = arp_lookup(ipaddr, dev, false);
   if (tabptr != NULL)
     {
       /* Notify to netlink */

net/netdev/netdev_findbyaddr.c

@@ -128,7 +128,8 @@ netdev_prefixlen_findby_lipv4addr(in_addr_t lipaddr, FAR int8_t *prefixlen)
 
               if (len > bestpref
 #ifdef CONFIG_NET_ARP
-                  || (len == bestpref && arp_find(lipaddr, NULL, dev) == OK)
+                  || (len == bestpref
+                      && arp_find(lipaddr, NULL, dev, true) == OK)
 #endif
                   )
                 {

net/netdev/netdev_ioctl.c

@@ -1452,7 +1452,7 @@ static int netdev_arp_ioctl(FAR struct socket *psock, int cmd,
               req->arp_pa.sa_family == AF_INET)
             {
               ret = arp_find(addr->sin_addr.s_addr,
-                            (FAR uint8_t *)req->arp_ha.sa_data, dev);
+                            (FAR uint8_t *)req->arp_ha.sa_data, dev, true);
               if (ret >= 0)
                 {
                   /* Return the mapped hardware address. */