FILE: we don't support paused transfers using this protocol

Make sure that we detect such attempts and return a proper error code
instead of silently handling this in problematic ways.

Updated the documentation to mention this limitation.

Bug: http://curl.haxx.se/bug/view.cgi?id=1286

2 files changed, 27 insertions, 9 deletions

diff --git a/lib/sendf.c b/lib/sendf.c
index c274203bf..8ffd43f47 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -444,10 +444,18 @@ CURLcode Curl_client_write(struct connectdata *conn,
       wrote = len;
     }
 
-    if(CURL_WRITEFUNC_PAUSE == wrote)
+    if(conn->handler->flags & PROTOPT_NONETWORK) {
+      /* protocols that work without network cannot be paused. This is
+         actually only FILE:// just now, and it can't pause since the transfer
+         isn't done using the "normal" procedure. */
+      failf(data, "Write callback asked for PAUSE when not supported!");
+      return CURLE_WRITE_ERROR;
+    }
+
+    else if(CURL_WRITEFUNC_PAUSE == wrote)
       return pausewrite(data, type, ptr, len);
 
-    if(wrote != len) {
+    else if(wrote != len) {
       failf(data, "Failed writing body (%zu != %zu)", wrote, len);
       return CURLE_WRITE_ERROR;
     }
diff --git a/lib/transfer.c b/lib/transfer.c
index 2ce6597c3..4dbc4e1b7 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -128,14 +128,24 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
     return CURLE_ABORTED_BY_CALLBACK;
   }
   else if(nread == CURL_READFUNC_PAUSE) {
-    struct SingleRequest *k = &data->req;
-    /* CURL_READFUNC_PAUSE pauses read callbacks that feed socket writes */
-    k->keepon |= KEEP_SEND_PAUSE; /* mark socket send as paused */
-    if(data->req.upload_chunky) {
-      /* Back out the preallocation done above */
-      data->req.upload_fromhere -= (8 + 2);
+
+    if(conn->handler->flags & PROTOPT_NONETWORK) {
+      /* protocols that work without network cannot be paused. This is
+         actually only FILE:// just now, and it can't pause since the transfer
+         isn't done using the "normal" procedure. */
+      failf(data, "Read callback asked for PAUSE when not supported!");
+      return CURLE_READ_ERROR;
+    }
+    else {
+      struct SingleRequest *k = &data->req;
+      /* CURL_READFUNC_PAUSE pauses read callbacks that feed socket writes */
+      k->keepon |= KEEP_SEND_PAUSE; /* mark socket send as paused */
+      if(data->req.upload_chunky) {
+        /* Back out the preallocation done above */
+        data->req.upload_fromhere -= (8 + 2);
+      }
+      *nreadp = 0;
     }
-    *nreadp = 0;
     return CURLE_OK; /* nothing was read */
   }
   else if((size_t)nread > buffersize) {