lwIP-v2: new patch to randomize tcp source ports (#5906)

ref: d-a-v/esp82xx-nonos-linklayer#31
origin: #5902
me-no-dev/ESPAsyncTCP#108

Following the links above is instructive.
To summarize:

    * currently and from a long time lwIP tcp client connections always uses the same tcp source port number right after boot
    * this port number is increased everytime a new one is needed (= new tcp client connection)
      (to be noted, linux has the same increasing behavior)
    * when connecting to the same server (right after boot), the triplet (esp-ip-address, source port, destination port) are the same, and may hit remote server list of sockets in time-wait-state (previous connection unproperly closed from the same esp). Consequently the new connection fails when it happens.
    * this is happening only when debugging (esp reboots often, in less time than time-wait expiration), so the nasty effect is amplified especially when bugs are being chased
    * efforts had been done when espressif's lwIP implementation wasn't open source, with WiFiClient::setLocalPortStart() #632 but it must be explicitely called with a different random number at every reboot. Efficient but not ideal.

This PR uses espressif firmware's r_rand() everytime a new local source port is needed. A different source port number is now showed by tcpdump right after boot. Source port range and duplication is verified everytime in lwIP's src/core/tcp.c:tcp_new_port(). It is implemented as a local patch for upstream lwIP so it is valid not only with WiFiClient but also with @me-no-dev's Async libraries (they don't use WiFiClient).

WiFiClient::setLocalPortStart() is still usable with the same effects as before.

Author: d-a-v

tools/sdk/lib/liblwip2-1460-feat.a

@@ -18,7 +18,11 @@
 #define ULWIPDEBUG	0	// 0 or 1 (trigger lwip debug)
 #define ULWIPASSERT	0	// 0 or 1 (trigger lwip self-check, 0 saves flash)
 
+#if ARDUINO
 #define STRING_IN_FLASH 1	// *print("fmt is stored in flash")
+#else
+#define STRING_IN_FLASH 0	// *print("fmt is stored in flash")
+#endif
 
 #define ROTBUFLEN_BIT	11	// (UDEBUGSTORE=1) doprint()'s buffer: 11=2048B
 
@@ -39,7 +43,9 @@ extern "C"
 void (*phy_capture) (int netif_idx, const char* data, size_t len, int out, int success);
 
 /////////////////////////////////////////////////////////////////////////////
+#if ARDUINO
 #include <sys/pgmspace.h>
+#endif
 
 #if UDEBUG && UDEBUGSTORE
 #warning use 'doprint_allow=1' right after Serial is enabled
@@ -94,6 +100,7 @@ int doprint_minus (const char* format, ...) __attribute__ ((format (printf, 1, 2
 #define uprint(x...)		do { (void)0; } while (0)
 #endif
 
+#if ARDUINO
 #define udoassert(assertion...)	\
 do { if ((assertion) == 0) { \
 		static const char assrt[] ICACHE_RODATA_ATTR STORE_ATTR = #assertion " wrong@"; \
@@ -104,6 +111,9 @@ do { if ((assertion) == 0) { \
 		os_printf_plus(assrt_line, __LINE__); \
 		uhalt(); \
 } } while (0)
+#else
+#define udoassert(assertion...)   do { if ((assertion) == 0) { os_printf("assert fail: " #assertion " @%s:%d\n", __FILE__, __LINE__); uhalt(); } } while (0)
+#endif
 
 #if UNDEBUG
 #define uassert(assertion...)	do { (void)0; } while (0)

tools/sdk/lib/liblwip2-1460.a

@@ -1,5 +1,5 @@
 // generated by makefiles/make-lwip2-hash
 #ifndef LWIP_HASH_H
 #define LWIP_HASH_H
-#define LWIP_HASH_STR "STABLE-2_1_2_RELEASE/glue:1.1-2-ga501b57"
+#define LWIP_HASH_STR "STABLE-2_1_2_RELEASE/glue:1.1-5-g25d5e81"
 #endif // LWIP_HASH_H

tools/sdk/lib/liblwip2-536-feat.a

@@ -3534,6 +3534,12 @@
 #error LWIP_FEATURES must be defined
 #endif
 
+
+/**
+ * TCP_RANDOM_PORT: randomize port instead of simply increasing
+ */
+#define TCP_RANDOM_PORT 1
+
 /*
    --------------------------------------------------
    ------------------ SNTP options ------------------