Improve TFTP implementation

- implement server/client mode (API is nicer to use)
- Increase TFTP_MAX_MODE_LEN to be able to contain "netascii" transfer mode
- Adapt tftp_example to changes

src/include/lwip/apps/tftp_client.h

@@ -37,6 +37,7 @@
 
 #include "lwip/apps/tftp_common.h"
 
+err_t tftp_init_client(const struct tftp_context* ctx);
 err_t tftp_get(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode);
 err_t tftp_put(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode);
 

src/include/lwip/apps/tftp_common.h

@@ -94,7 +94,11 @@ struct tftp_context {
   void (*error)(void* handle, int err, const char* msg, int size);
 };
 
-err_t tftp_init(const struct tftp_context* ctx);
+#define LWIP_TFTP_MODE_SERVER       0x01
+#define LWIP_TFTP_MODE_CLIENT       0x02
+#define LWIP_TFTP_MODE_CLIENTSERVER (LWIP_TFTP_MODE_SERVER | LWIP_TFTP_MODE_CLIENT)
+
+err_t tftp_init_common(u8_t mode, const struct tftp_context* ctx);
 void tftp_cleanup(void);
 
 #ifdef __cplusplus

src/include/lwip/apps/tftp_opts.h

@@ -96,7 +96,7 @@
  * Max. length of TFTP mode
  */
 #if !defined TFTP_MAX_MODE_LEN || defined __DOXYGEN__
-#define TFTP_MAX_MODE_LEN     7
+#define TFTP_MAX_MODE_LEN     10
 #endif
 
 /**

src/include/lwip/apps/tftp_server.h

@@ -5,7 +5,7 @@
  *
  */
 
-/* 
+/*
  * Redistribution and use in source and binary forms, with or without
  * modification,are permitted provided that the following conditions are met:
  *
@@ -37,4 +37,6 @@
 
 #include "lwip/apps/tftp_common.h"
 
+err_t tftp_init_server(const struct tftp_context* ctx);
+
 #endif /* LWIP_HDR_APPS_TFTP_SERVER_H */