From 07fbe82305418b219ea94e72f9f907455db54974 Mon Sep 17 00:00:00 2001
From: Simon Goldschmidt <goldsimon@gmx.de>
Date: Sat, 22 Feb 2014 21:38:56 +0100
Subject: [PATCH] fixed bug #34681 Limit ARP queue length by ARP_QUEUE_LEN (=3)

---
 CHANGELOG              |  3 +++
 src/include/lwip/opt.h |  8 ++++++++
 src/netif/etharp.c     | 12 ++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/CHANGELOG b/CHANGELOG
index 29701cfd..d646560e 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -96,6 +96,9 @@ HISTORY
 
  ++ Bugfixes:
 
+ 2014-02-22: Simon Goldschmidt (patch by Amir Shalem)
+  * etharp.c, opt.h: fixed bug #34681 Limit ARP queue length by ARP_QUEUE_LEN (=3)
+
   2014-02-22: Simon Goldschmidt (patch by Amir Shalem)
   * etharp.h/.c: fixed bug #34682 Limit ARP request flood for unresolved entry
 
diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index d8cf3491..9ba9efd4 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -481,6 +481,14 @@
 #define ARP_QUEUEING                    0
 #endif
 
+/** The maximum number of packets which may be queued for each
+ *  unresolved address by other network layers. Defaults to 3, 0 means disabled.
+ *  Old packets are dropped, new packets are queued.
+ */ 
+#ifndef ARP_QUEUE_LEN
+#define ARP_QUEUE_LEN 3
+#endif
+
 /**
  * ETHARP_TRUST_IP_MAC==1: Incoming IP packets cause the ARP table to be
  * updated with the source MAC and IP addresses supplied in the packet.
diff --git a/src/netif/etharp.c b/src/netif/etharp.c
index fd9e0de1..87c423e7 100644
--- a/src/netif/etharp.c
+++ b/src/netif/etharp.c
@@ -1140,20 +1140,32 @@ etharp_query(struct netif *netif, ip_addr_t *ipaddr, struct pbuf *q)
       /* allocate a new arp queue entry */
       new_entry = (struct etharp_q_entry *)memp_malloc(MEMP_ARP_QUEUE);
       if (new_entry != NULL) {
+        unsigned int qlen = 0;
         new_entry->next = 0;
         new_entry->p = p;
         if(arp_table[i].q != NULL) {
           /* queue was already existent, append the new entry to the end */
           struct etharp_q_entry *r;
           r = arp_table[i].q;
+          qlen++;
           while (r->next != NULL) {
             r = r->next;
+            qlen++;
           }
           r->next = new_entry;
         } else {
           /* queue did not exist, first item in queue */
           arp_table[i].q = new_entry;
         }
+#if ARP_QUEUE_LEN
+        if (qlen >= ARP_QUEUE_LEN) {
+          struct etharp_q_entry *old;
+          old = arp_table[i].q;
+          arp_table[i].q = arp_table[i].q->next;
+          pbuf_free(old->p);
+          memp_free(MEMP_ARP_QUEUE, old);
+        }
+#endif
         LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("etharp_query: queued packet %p on ARP entry %"S16_F"\n", (void *)q, (s16_t)i));
         result = ERR_OK;
       } else {