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

contrib/examples/tftp/tftp_example.c

@@ -32,6 +32,8 @@
 #include "lwip/apps/tftp_server.h"
 #include "tftp_example.h"
 
+#include <string.h>
+
 #if LWIP_UDP
 
 static void*
@@ -75,17 +77,31 @@ tftp_write(void* handle, struct pbuf* p)
   return 0;
 }
 
+static int
+tftp_error(void* handle, int err, const char* msg, int size)
+{
+  char message[100];
+
+  memset(message, 0, sizeof(message));
+  MEMCPY(message, msg, LWIP_MIN(sizeof(message)-1, size));
+
+  printf("TFTP error: %d (%s)", err, message);
+
+  return 0;
+}
+
 static const struct tftp_context tftp = {
   tftp_open,
   tftp_close,
   tftp_read,
-  tftp_write
+  tftp_write,
+  tftp_error
 };
 
 void
 tftp_example_init(void)
 {
-  tftp_init(&tftp);
+  tftp_init_server(&tftp);
 }
 
 #endif /* LWIP_UDP */

src/apps/tftp/tftp.c

@@ -91,6 +91,7 @@ struct tftp_state {
 };
 
 static struct tftp_state tftp_state;
+static u8_t tftp_mode;
 
 static void tftp_tmr(void *arg);
 
@@ -261,6 +262,11 @@ recv(void *arg, struct udp_pcb *upcb, struct pbuf *p, const ip_addr_t *addr, u16
         break;
       }
 
+      if ((tftp_mode & LWIP_TFTP_MODE_SERVER) == 0) {
+        send_error(addr, port, TFTP_ERROR_ACCESS_VIOLATION, "TFTP server not enabled");
+        break;
+      }
+
       sys_timeout(TFTP_TIMER_MSECS, tftp_tmr, NULL);
 
       /* find \0 in pbuf -> end of filename string */
@@ -420,12 +426,13 @@ tftp_tmr(void *arg)
   }
 }
 
-/** @ingroup tftp
+/**
  * Initialize TFTP client/server.
+ * @param mode TFTP mode (client/server)
  * @param ctx TFTP callback struct
  */
 err_t
-tftp_init(const struct tftp_context *ctx)
+tftp_init_common(u8_t mode, const struct tftp_context *ctx)
 {
   err_t ret;
 
@@ -435,6 +442,8 @@ tftp_init(const struct tftp_context *ctx)
     return ERR_MEM;
   }
 
+  tftp_mode = mode;
+
   ret = udp_bind(pcb, IP_ANY_TYPE, TFTP_PORT);
   if (ret != ERR_OK) {
     udp_remove(pcb);
@@ -453,6 +462,26 @@ tftp_init(const struct tftp_context *ctx)
   return ERR_OK;
 }
 
+/** @ingroup tftp
+ * Initialize TFTP server.
+ * @param ctx TFTP callback struct
+ */
+err_t
+tftp_init_server(const struct tftp_context *ctx)
+{
+  return tftp_init_common(LWIP_TFTP_MODE_SERVER, ctx);
+}
+
+/** @ingroup tftp
+ * Initialize TFTP client.
+ * @param ctx TFTP callback struct
+ */
+err_t
+tftp_init_client(u8_t mode, const struct tftp_context *ctx)
+{
+  return tftp_init_common(LWIP_TFTP_MODE_CLIENT, ctx);
+}
+
 /** @ingroup tftp
  * Deinitialize ("turn off") TFTP client/server.
  */
@@ -465,7 +494,10 @@ void tftp_cleanup(void)
 }
 
 err_t
-tftp_get(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode) {
+tftp_get(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode)
+{
+  LWIP_ERROR("TFTP client is not enabled (tftp_init)", (tftp_mode & LWIP_TFTP_MODE_CLIENT) == 0, return ERR_VAL);
+
   tftp_state.handle = handle;
   tftp_state.blknum = 1;
   tftp_state.mode_write = 1; // We want to receive data
@@ -474,7 +506,10 @@ tftp_get(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, con
 }
 
 err_t
-tftp_put(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode) {
+tftp_put(void* handle, const ip_addr_t *addr, u16_t port, const char* fname, const char* mode)
+{
+  LWIP_ERROR("TFTP client is not enabled (tftp_init)", (tftp_mode & LWIP_TFTP_MODE_CLIENT) == 0, return ERR_VAL);
+
   tftp_state.handle = handle;
   tftp_state.blknum = 1;
   tftp_state.mode_write = 0; // We want to send data

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

@@ -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 */