lwip: added configuration values for echo interval

components/lwip/Kconfig

@@ -768,6 +768,24 @@ menu "LWIP"
 
     endmenu # SNTP
 
+    menu "LCP"
+
+        config LCP_ECHOINTERVAL
+            int "Echo interval (s)"
+            range 0 1000000
+            default 0
+            help
+                Interval in seconds between keepalive LCP echo requests, 0 to disable.
+
+        config LCP_MAXECHOFAILS
+            int "Maximum echo failures"
+            range 0 100000
+            default 3
+            help
+                Number of consecutive unanswered echo requests before failure is indicated.
+
+    endmenu # LCP
+
     config LWIP_ESP_LWIP_ASSERT
         bool "Enable LWIP ASSERT checks"
         default y

components/lwip/port/esp32/include/lwipopts.h

@@ -733,7 +733,23 @@
 #define PPP_DEBUG                       LWIP_DBG_OFF
 #endif
 
-#endif
+#endif  /* PPP SUPPORT */
+
+/*
+   ------------------------------------
+   --------- LCP Echo options ---------
+   ------------------------------------
+*/
+/**
+ * LCP_ECHOINTERVAL: Interval in seconds between keepalive LCP echo requests, 0 to disable.
+ */
+#define LCP_ECHOINTERVAL                CONFIG_LCP_ECHOINTERVAL
+
+/**
+ * LCP_MAXECHOFAILS: Number of consecutive unanswered echo requests before failure is indicated.
+ */
+#define LCP_MAXECHOFAILS                CONFIG_LCP_MAXECHOFAILS
+
 
 /*
    --------------------------------------