- When libcurl was doing a HTTP POST and the server would respond with

"Connection: close" and actually close the connection after the
  response-body, libcurl could still have outstanding data to send and it
  would not properly notice this and stop sending. This caused weirdness and
  sad faces. http://curl.haxx.se/bug/view.cgi?id=2080222

  Note that there are still reasons to consider libcurl's behavior when
  getting a >= 400 response code while sending data, as Craig Perras' note
  "http upload: how to stop on error" specifies:
  http://curl.haxx.se/mail/archive-2008-08/0138.html

lib/transfer.c

@@ -656,6 +656,15 @@ static CURLcode readwrite_data(struct SessionHandle *data,
 
   } while(data_pending(conn));
 
+  if(((k->keepon & (KEEP_READ|KEEP_WRITE)) == KEEP_WRITE) &&
+     conn->bits.close ) {
+    /* When we've read the entire thing and the close bit is set, the server may
+       now close the connection. If there's now any kind of sending going on from
+       our side, we need to stop that immediately. */
+    infof(data, "we are done reading and this is set to close, stop send\n");
+    k->keepon &= ~KEEP_WRITE; /* no writing anymore either */
+  }
+
   return CURLE_OK;
 }