- Bug report #2709004 (http://curl.haxx.se/bug/view.cgi?id=2709004) by Tim

  Chen pointed out how curl couldn't upload with resume when reading from a
  pipe.

  This ended up with the introduction of a new return code for the
  CURLOPT_SEEKFUNCTION callback that basically says that the seek failed but
  that libcurl may try to resolve the situation anyway. In our case this means
  libcurl will attempt to instead read that much data from the stream instead
  of seeking and that way curl can now upload with resume when data is read
  from a stream!

1 files changed, 32 insertions, 27 deletions

diff --git a/lib/ssh.c b/lib/ssh.c
index 2de1cf86d..d473d1400 100644
--- a/lib/ssh.c
+++ b/lib/ssh.c
@@ -463,6 +463,7 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
   const char *host_public_key_md5;
   int rc = LIBSSH2_ERROR_NONE, i;
   int err;
+  int seekerr = CURL_SEEKFUNC_OK;
   *block = 0; /* we're not blocking by default */
 
   switch(sshc->state) {
@@ -1315,37 +1316,41 @@ static CURLcode ssh_statemach_act(struct connectdata *conn, bool *block)
     if(data->state.resume_from > 0) {
       /* Let's read off the proper amount of bytes from the input. */
       if(conn->seek_func) {
-        curl_off_t readthisamountnow = data->state.resume_from;
+        seekerr = conn->seek_func(conn->seek_client, data->state.resume_from,
+                                  SEEK_SET);
+      }
+
+      if(seekerr != CURL_SEEKFUNC_OK){
 
-        if(conn->seek_func(conn->seek_client,
-                           readthisamountnow, SEEK_SET) != 0) {
+        if(seekerr != CURL_SEEKFUNC_CANTSEEK) {
           failf(data, "Could not seek stream");
           return CURLE_FTP_COULDNT_USE_REST;
         }
-      }
-      else {
-        curl_off_t passed=0;
-        curl_off_t readthisamountnow;
-        curl_off_t actuallyread;
-        do {
-          readthisamountnow = (data->state.resume_from - passed);
-
-          if(readthisamountnow > BUFSIZE)
-            readthisamountnow = BUFSIZE;
-
-          actuallyread =
-            (curl_off_t) conn->fread_func(data->state.buffer, 1,
-                                          (size_t)readthisamountnow,
-                                          conn->fread_in);
-
-          passed += actuallyread;
-          if((actuallyread <= 0) || (actuallyread > readthisamountnow)) {
-            /* this checks for greater-than only to make sure that the
-               CURL_READFUNC_ABORT return code still aborts */
-             failf(data, "Failed to read data");
-            return CURLE_FTP_COULDNT_USE_REST;
-          }
-        } while(passed < data->state.resume_from);
+        /* seekerr == CURL_SEEKFUNC_CANTSEEK (can't seek to offset) */
+        else {
+          curl_off_t passed=0;
+          curl_off_t readthisamountnow;
+          curl_off_t actuallyread;
+          do {
+            readthisamountnow = (data->state.resume_from - passed);
+
+            if(readthisamountnow > BUFSIZE)
+              readthisamountnow = BUFSIZE;
+
+            actuallyread =
+              (curl_off_t) conn->fread_func(data->state.buffer, 1,
+                                            (size_t)readthisamountnow,
+                                            conn->fread_in);
+
+            passed += actuallyread;
+            if((actuallyread <= 0) || (actuallyread > readthisamountnow)) {
+              /* this checks for greater-than only to make sure that the
+                 CURL_READFUNC_ABORT return code still aborts */
+              failf(data, "Failed to read data");
+              return CURLE_FTP_COULDNT_USE_REST;
+            }
+          } while(passed < data->state.resume_from);
+        }
       }
 
       /* now, decrease the size of the read */