[lwip]:add MEMP_NUM_NETCONN option for lwip

components/net/Kconfig

@@ -98,6 +98,10 @@ config RT_USING_LWIP
         config RT_LWIP_PPPOS
             bool "PPPoS protocol"
             default n
+            
+        config RT_MEMP_NUM_NETCONN
+            int "the number of struct netconns"
+            default 8
 
         config RT_LWIP_PBUF_NUM
             int "the number of PBUF"

components/net/lwip-2.0.2/src/lwipopts.h

@@ -105,6 +105,11 @@
    should be set high. */
 #define MEMP_NUM_PBUF               32 //16
 
+/* the number of struct netconns */
+#ifdef RT_MEMP_NUM_NETCONN
+#define MEMP_NUM_NETCONN            RT_MEMP_NUM_NETCONN
+#endif
+
 /* the number of UDP protocol control blocks. One per active RAW "connection". */
 #ifdef RT_LWIP_RAW_PCB_NUM
 #define MEMP_NUM_RAW_PCB            RT_LWIP_RAW_PCB_NUM