lwip2 fix and update (#4729)

* interactive example: update with option for using DHCP again after using static IP
* lwip2: avoid crash when IP address is set to 0(any) by dhcp not getting its lease renewal in due time
* lwip2: automatically remove oldest PCBs in time-wait state, limit their number
  thanks to @me-no-dev 07f4d4c241 (diff-f8258e71e25fb9985ca3799e3d8b88ecR399)
* faq: update about tcpCleanup()
* lwip2: add a macro HAS_PHY_CAPTURE=1 indicating capture facility is available

doc/faq/readme.rst

@@ -93,8 +93,15 @@ This error may pop up after switching between
 How to clear TCP PCBs in time-wait state ?
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-This is needed with lwIP-v1.4, less needed with lwIP-v2 but timeout is still
-too high.
+This is not needed anymore:
+
+PCBs in time-wait state are limited to 5 and removed when that number is
+exceeded.
+
+Ref.  `lwIP-v1.4 <https://github.com/esp8266/Arduino/commit/07f4d4c241df2c552899857f39a4295164f686f2#diff-f8258e71e25fb9985ca3799e3d8b88ecR399>`__,
+`lwIP-v2 <https://github.com/d-a-v/esp82xx-nonos-linklayer/commit/420960dfc0dbe07114f7364845836ac333bc84f7>`__
+
+For reference:
 
 Time-wait PCB state helps TCP not confusing two consecutive connections with the
 same (s-ip,s-port,d-ip,d-port) when the first is already closed but still

libraries/esp8266/examples/interactive/interactive.ino

@@ -85,7 +85,7 @@ void loop() {
     case 'n': DO(WiFi.setSleepMode(WIFI_NONE_SLEEP));
     case 'l': DO(WiFi.setSleepMode(WIFI_LIGHT_SLEEP));
     case 'm': DO(WiFi.setSleepMode(WIFI_MODEM_SLEEP));
-    case 's': DO(WiFi.config(staticip, gateway, subnet));
-    case 'D': DO(wifi_station_dhcpc_start());
+    case 'S': DO(WiFi.config(staticip, gateway, subnet)); // use static address
+    case 's': DO(WiFi.config(0u, 0u, 0u));                // back to dhcp client
   }
 }

tools/sdk/lwip2/builder

@@ -1 +1 @@
-Subproject commit 2b827f842925b2daf12b67ab1ae498e58174124e
+Subproject commit 0c0d8c2fb90de1fc1a956c89984b74dcdd7bf8dc

tools/sdk/lwip2/include/gluedebug.h

@@ -35,6 +35,7 @@
 #ifdef __cplusplus
 extern "C"
 #endif
+#define HAS_PHY_CAPTURE 1
 void (*phy_capture) (int netif_idx, const char* data, size_t len, int out, int success);
 
 /////////////////////////////////////////////////////////////////////////////

tools/sdk/lwip2/include/lwip-git-hash.h

@@ -1,5 +1,5 @@
 // generated by makefiles/make-lwip2-hash
 #ifndef LWIP_HASH_H
 #define LWIP_HASH_H
-#define LWIP_HASH_STR "STABLE-2_0_3_RELEASE/glue:arduino-2.4.1-7-g2b827f8"
+#define LWIP_HASH_STR "STABLE-2_0_3_RELEASE/glue:arduino-2.4.1-10-g0c0d8c2"
 #endif // LWIP_HASH_H

tools/sdk/lwip2/include/lwipopts.h

@@ -2997,6 +2997,7 @@
 
 /*
    --------------------------------------------------
+   ------------- End of original lwipopts -----------
    --------------------------------------------------
 */
 
@@ -3013,4 +3014,34 @@ struct netif;
 #endif
 LWIP_ERR_T lwip_unhandled_packet (struct pbuf* pbuf, struct netif* netif) __attribute__((weak));
 
+/*
+   --------------------------------------------------
+   ----------------- TIME-WAIT tweak ----------------
+   --------------------------------------------------
+   port @me-no-dev time-wait tweak
+   https://github.com/esp8266/Arduino/commit/07f4d4c241df2c552899857f39a4295164f686f2#diff-f8258e71e25fb9985ca3799e3d8b88ecR399
+*/
+
+void tcp_kill_timewait (void);
+#define TCP_TW_LIMIT(l)                \
+  if (l) do {                          \
+    u32_t count_plus_1 = 1;            \
+    struct tcp_pcb* tmp = tcp_tw_pcbs; \
+    if (tmp)                           \
+      while ((tmp = tmp->next))        \
+        ++count_plus_1;                \
+    while (--count_plus_1 > (l))       \
+      /* kill the oldest */            \
+      /* pcb in TW state */            \
+      tcp_kill_timewait();             \
+  } while (0)
+
+/**
+ * MEMP_NUM_TCP_PCB_TIME_WAIT: the number of TCP pcbs in TIME_WAIT state.
+ * (requires the LWIP_TCP option, 0 = disabled)
+ */
+#ifndef MEMP_NUM_TCP_PCB_TIME_WAIT
+#define MEMP_NUM_TCP_PCB_TIME_WAIT       5
+#endif
+
 #endif // MYLWIPOPTS_H