Fix BUG#11400 - don't corrupt existing pbuf chain when enqueuing multiple pbufs to a pending ARP request

src/include/lwip/memp.h

@@ -46,7 +46,9 @@ typedef enum {
   MEMP_NETBUF,
   MEMP_NETCONN,
   MEMP_TCPIP_MSG,
-
+#if ARP_QUEUEING
+  MEMP_ARP_QUEUE,
+#endif
   MEMP_SYS_TIMEOUT,
   
   MEMP_MAX

src/include/lwip/opt.h

@@ -107,6 +107,12 @@ a lot of data that needs to be copied, this should be set high. */
 #ifndef MEMP_NUM_TCP_SEG
 #define MEMP_NUM_TCP_SEG                16
 #endif
+/* MEMP_NUM_ARP_QUEUE: the number of simulateously queued outgoing
+   packets (pbufs) that are waiting for an ARP request (to resolve
+   their destination address) to finish. */
+#ifndef MEMP_NUM_ARP_QUEUE
+#define MEMP_NUM_ARP_QUEUE              30
+#endif
 /* MEMP_NUM_SYS_TIMEOUT: the number of simulateously active
    timeouts. */
 #ifndef MEMP_NUM_SYS_TIMEOUT

src/include/netif/etharp.h

@@ -113,6 +113,15 @@ PACK_STRUCT_END
 #define ETHTYPE_ARP 0x0806
 #define ETHTYPE_IP  0x0800
 
+#if ARP_QUEUEING
+/** struct for queueing outgoing packets for unknown address
+  * defined here to be accessed by memp.h
+  */
+struct etharp_q_entry {
+  struct etharp_q_entry *next;
+  struct pbuf *p;
+};
+#endif
 
 void etharp_init(void);
 void etharp_tmr(void);