TFTP: add option to suppress TFTP option requests (Part 1)

Some TFTP server implementations ignore the "TFTP Option extension"
(RFC 1782-1784, 2347-2349), or implement it in a flawed way, causing
problems with libcurl. Another switch for curl_easy_setopt
"CURLOPT_TFTP_NO_OPTIONS" is introduced which prevents libcurl from
sending TFTP option requests to a server, avoiding many problems caused
by faulty implementations.

Bug: https://github.com/curl/curl/issues/481

3 files changed, 40 insertions, 29 deletions

diff --git a/lib/tftp.c b/lib/tftp.c
index 040d967b0..eec774b3e 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -494,33 +494,36 @@ static CURLcode tftp_send_first(tftp_state_data_t *state, tftp_event_t event)
              "%s%c%s%c", filename, '\0',  mode, '\0');
     sbytes = 4 + strlen(filename) + strlen(mode);
 
-    /* add tsize option */
-    if(data->set.upload && (data->state.infilesize != -1))
-      snprintf(buf, sizeof(buf), "%" CURL_FORMAT_CURL_OFF_T,
-               data->state.infilesize);
-    else
-      strcpy(buf, "0"); /* the destination is large enough */
-
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes,
-                              TFTP_OPTION_TSIZE);
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes, buf);
-    /* add blksize option */
-    snprintf( buf, sizeof(buf), "%d", state->requested_blksize );
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes,
-                              TFTP_OPTION_BLKSIZE);
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes, buf );
-
-    /* add timeout option */
-    snprintf( buf, sizeof(buf), "%d", state->retry_time);
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes,
-                              TFTP_OPTION_INTERVAL);
-    sbytes += tftp_option_add(state, sbytes,
-                              (char *)state->spacket.data+sbytes, buf );
+    /* optional addition of TFTP options */
+    if(!data->set.tftp_no_options) {
+      /* add tsize option */
+      if(data->set.upload && (data->state.infilesize != -1))
+        snprintf(buf, sizeof(buf), "%" CURL_FORMAT_CURL_OFF_T,
+                 data->state.infilesize);
+      else
+        strcpy(buf, "0"); /* the destination is large enough */
+
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes,
+                                TFTP_OPTION_TSIZE);
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes, buf);
+      /* add blksize option */
+      snprintf(buf, sizeof(buf), "%d", state->requested_blksize);
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes,
+                                TFTP_OPTION_BLKSIZE);
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes, buf );
+
+      /* add timeout option */
+      snprintf(buf, sizeof(buf), "%d", state->retry_time);
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes,
+                                TFTP_OPTION_INTERVAL);
+      sbytes += tftp_option_add(state, sbytes,
+                                (char *)state->spacket.data+sbytes, buf );
+    }
 
     /* the typecase for the 3rd argument is mostly for systems that do
        not have a size_t argument, like older unixes that want an 'int' */
diff --git a/lib/url.c b/lib/url.c
index 576b8e88c..bf293a4d9 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -843,9 +843,16 @@ CURLcode Curl_setopt(struct SessionHandle *data, CURLoption option,
      */
     data->set.server_response_timeout = va_arg( param , long ) * 1000;
     break;
+  case CURLOPT_TFTP_NO_OPTIONS:
+    /*
+     * Option that prevents libcurl from sending TFTP option requests to the
+     * server.
+     */
+    data->set.tftp_no_options = va_arg(param, long) != 0;
+    break;
   case CURLOPT_TFTP_BLKSIZE:
     /*
-     * TFTP option that specifies the block size to use for data transmission
+     * TFTP option that specifies the block size to use for data transmission.
      */
     data->set.tftp_blksize = va_arg(param, long);
     break;
diff --git a/lib/urldata.h b/lib/urldata.h
index ab26c0111..fcb17561d 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1499,7 +1499,8 @@ struct UserDefined {
   long connecttimeout;  /* in milliseconds, 0 means no timeout */
   long accepttimeout;   /* in milliseconds, 0 means no timeout */
   long server_response_timeout; /* in milliseconds, 0 means no timeout */
-  long tftp_blksize ; /* in bytes, 0 means use default */
+  long tftp_blksize;    /* in bytes, 0 means use default */
+  bool tftp_no_options; /* do not send TFTP options requests */
   curl_off_t filesize;  /* size of file to upload, -1 means unknown */
   long low_speed_limit; /* bytes/second */
   long low_speed_time;  /* number of seconds */