Merge branch 'bugfix/add_tx_flowcontrol' into 'master'

lwip: add socket tx flow control

This fix is used to solve wifi q full issue:
1. When wifi tx q is full, set tx_enable to false
2. When wifi tx q decrease 1/2 max length, set tx_enable to true again
3. esp_wifi_tx_enable return whether tx_enable is true
4. If esp_wifi_tx_enable return false, socket will be blocked

See merge request !62

components/lwip/api/sockets.c

@@ -388,19 +388,30 @@ static void lwip_socket_drop_registered_memberships(int s);
 #endif /* LWIP_IGMP */
 
 #ifdef LWIP_ESP8266
-extern size_t system_get_free_heap_size(void);
 
-#define DELAY_WHEN_MEMORY_NOT_ENOUGH() \
-do{\
-  uint8_t _wait_delay = 0;\
-  while (system_get_free_heap_size() < HEAP_HIGHWAT){\
-     vTaskDelay(_wait_delay/portTICK_RATE_MS);\
-     if (_wait_delay < 64) _wait_delay *= 2;\
-  }\
-}while(0)
+/* Since esp_wifi_tx_is_stop/system_get_free_heap_size are not an public wifi API, so extern them here*/
+extern size_t system_get_free_heap_size(void);
+extern bool esp_wifi_tx_is_stop(void);
+
+/* Please be notified that this flow control is just a workaround for fixing wifi Q full issue. 
+ * Under UDP/TCP pressure test, we found that the sockets may cause wifi tx queue full if the socket
+ * sending speed is faster than the wifi sending speed, it will finally cause the packet to be dropped
+ * in wifi layer, it's not acceptable in some application. That's why we introdue the tx flow control here.
+ * However, current solution is just a workaround, we need to consider the return value of wifi tx interface,
+ * and feedback the return value to lwip and let lwip do the flow control itself.
+ */ 
+static inline void esp32_tx_flow_ctrl(void)
+{
+  uint8_t _wait_delay = 0;
+
+  while ((system_get_free_heap_size() < HEAP_HIGHWAT) || esp_wifi_tx_is_stop()){
+     vTaskDelay(_wait_delay/portTICK_RATE_MS);
+     if (_wait_delay < 64) _wait_delay *= 2;
+  }
+}
 
 #else
-#define DELAY_WHEN_MEMORY_NOT_ENOUGH() 
+#define esp32_tx_flow_ctrl() 
 #endif
 
 /** The global array of available sockets */
@@ -1219,7 +1230,7 @@ lwip_send(int s, const void *data, size_t size, int flags)
 #endif /* (LWIP_UDP || LWIP_RAW) */
   }
 
-  DELAY_WHEN_MEMORY_NOT_ENOUGH();
+  esp32_tx_flow_ctrl();
 
   write_flags = NETCONN_COPY |
     ((flags & MSG_MORE)     ? NETCONN_MORE      : 0) |
@@ -1402,7 +1413,7 @@ lwip_sendto(int s, const void *data, size_t size, int flags,
 #endif /* LWIP_TCP */
   }
 
-  DELAY_WHEN_MEMORY_NOT_ENOUGH();
+  esp32_tx_flow_ctrl();
 
   if ((to != NULL) && !SOCK_ADDR_TYPE_MATCH(to, sock)) {
     /* sockaddr does not match socket type (IPv4/IPv6) */

components/lwip/include/lwip/port/arch/sys_arch.h

@@ -68,7 +68,5 @@ void sys_delay_ms(uint32_t ms);
 sys_sem_t* sys_thread_sem_init(void);
 void sys_thread_sem_deinit(void);
 sys_sem_t* sys_thread_sem_get(void);
-
-
 #endif /* __SYS_ARCH_H__ */