ftp: close connection as soon as ABOR has been sent

... and do not send ABOR unless really necessary.

Bug: https://bugzilla.redhat.com/649347
Reported by: Simon H.

lib/ftp.c

@@ -3083,10 +3083,9 @@ static CURLcode ftp_done(struct connectdata *conn, CURLcode status,
 #endif
 
   if(conn->sock[SECONDARYSOCKET] != CURL_SOCKET_BAD) {
-    if(!result && ftpc->dont_check)
-      /* prevent some FTP servers (namely Pure-ftpd) from hanging if we close
-       * the data channel before transferring all data */
-      result = Curl_pp_sendf(&ftpc->pp, "ABOR");
+    if(!result && ftpc->dont_check && data->req.maxdownload > 0)
+      /* partial download completed */
+      result = Curl_pp_sendf(pp, "ABOR");
 
     if(conn->ssl[SECONDARYSOCKET].use) {
       /* The secondary socket is using SSL so we must close down that part
@@ -3128,6 +3127,14 @@ static CURLcode ftp_done(struct connectdata *conn, CURLcode status,
     if(result)
       return result;
 
+    if(ftpc->dont_check && data->req.maxdownload > 0) {
+      /* we have just sent ABOR and there is no reliable way to check if it was
+       * successful or not; we have to close the connection now */
+      infof(data, "partial download completed, closing connection\n");
+      conn->bits.close = TRUE; /* mark for closure */
+      return result;
+    }
+
     if(!ftpc->dont_check) {
       /* 226 Transfer complete, 250 Requested file action okay, completed. */
       if((ftpcode != 226) && (ftpcode != 250)) {

tests/data/test1036

@@ -50,7 +50,6 @@ TYPE I
 SIZE 1036
 REST 20
 RETR 1036
-ABOR
 QUIT
 </protocol>
 <file name="log/curl1036.out">

tests/data/test110

@@ -46,7 +46,6 @@ TYPE I
 SIZE 110
 REST 20
 RETR 110
-ABOR
 QUIT
 </protocol>
 </verify>

tests/data/test122

@@ -39,7 +39,6 @@ EPSV
 PASV
 TYPE I
 SIZE 122
-ABOR
 QUIT
 </protocol>
 </verify>