curl: fix --upload-file . hangs if delay in STDIN

Attempt to unpause a busy read in the CURLOPT_XFERINFOFUNCTION.

When uploading from stdin in non-blocking mode, a delay in reading
the stream (EAGAIN) causes curl to pause sending data
(CURL_READFUNC_PAUSE).  Prior to this change, a busy read was
detected and unpaused only in the CURLOPT_WRITEFUNCTION handler.
This change performs the same busy read handling in a
CURLOPT_XFERINFOFUNCTION handler.

Fixes: curl#2051
Reported-by: @bdry

src/tool_cb_rea.c

@@ -27,6 +27,7 @@
 
 #include "tool_cfgable.h"
 #include "tool_cb_rea.h"
+#include "tool_operate.h"
 
 #include "memdebug.h" /* keep this as LAST include */
 
@@ -52,3 +53,28 @@ size_t tool_read_cb(void *buffer, size_t sz, size_t nmemb, void *userdata)
   in->config->readbusy = FALSE;
   return (size_t)rc;
 }
+
+/*
+** callback for CURLOPT_XFERINFOFUNCTION used to unpause busy reads
+*/
+
+int tool_readbusy_cb(void *clientp,
+                     curl_off_t dltotal, curl_off_t dlnow,
+                     curl_off_t ultotal, curl_off_t ulnow)
+{
+  struct per_transfer *per = clientp;
+  struct OutStruct *outs = &per->outs;
+  struct OperationConfig *config = outs->config;
+
+  (void)dltotal;  /* unused */
+  (void)dlnow;  /* unused */
+  (void)ultotal;  /* unused */
+  (void)ulnow;  /* unused */
+
+  if(config->readbusy) {
+    config->readbusy = FALSE;
+    curl_easy_pause(per->curl, CURLPAUSE_CONT);
+  }
+
+  return 0;
+}

src/tool_cb_rea.h

@@ -29,4 +29,12 @@
 
 size_t tool_read_cb(void *buffer, size_t sz, size_t nmemb, void *userdata);
 
+/*
+** callback for CURLOPT_XFERINFOFUNCTION used to unpause busy reads
+*/
+
+int tool_readbusy_cb(void *clientp,
+                     curl_off_t dltotal, curl_off_t dlnow,
+                     curl_off_t ultotal, curl_off_t ulnow);
+
 #endif /* HEADER_CURL_TOOL_CB_REA_H */

src/tool_operate.c

@@ -1088,6 +1088,12 @@ static CURLcode single_transfer(struct GlobalConfig *global,
           global->isatty = orig_isatty;
         }
 
+        if(per->uploadfile && !strcmp(per->uploadfile, ".")) {
+          /* when reading from stdin in non-blocking mode, we use the progress
+             function to unpause a busy read */
+          global->noprogress = FALSE;
+        }
+
         if(urlnum > 1 && !global->mute) {
           per->separator_err =
             aprintf("\n[%lu/%lu]: %s --> %s",
@@ -1575,6 +1581,12 @@ static CURLcode single_transfer(struct GlobalConfig *global,
           my_setopt(curl, CURLOPT_XFERINFOFUNCTION, tool_progress_cb);
           my_setopt(curl, CURLOPT_XFERINFODATA, &per->progressbar);
         }
+        else if(per->uploadfile && !strcmp(per->uploadfile, ".")) {
+          /* when reading from stdin in non-blocking mode, we use the progress
+             function to unpause a busy read */
+          my_setopt(curl, CURLOPT_XFERINFOFUNCTION, tool_readbusy_cb);
+          my_setopt(curl, CURLOPT_XFERINFODATA, per);
+        }
 
         /* new in libcurl 7.24.0: */
         if(config->dns_servers)