FTP: prevent the multi interface from blocking

As pointed out in Bug report #3579064, curl_multi_perform() would
wrongly use a blocking mechanism internally for some commands which
could lead to for example a very long block if the LIST response never
showed.

The solution was to make sure to properly continue to use the multi
interface non-blocking state machine.

The new test 1501 verifies the fix.

Bug: http://curl.haxx.se/bug/view.cgi?id=3579064
Reported by: Guido Berhoerster

lib/ftp.c

@@ -666,11 +666,18 @@ static CURLcode ftp_readresp(curl_socket_t sockfd,
   if(ftpcode)
     *ftpcode = code;
 
-  if(421 == code)
+  if(421 == code) {
     /* 421 means "Service not available, closing control connection." and FTP
      * servers use it to signal that idle session timeout has been exceeded.
-     * If we ignored the response, it could end up hanging in some cases. */
+     * If we ignored the response, it could end up hanging in some cases.
+     *
+     * This response code can come at any point so having it treated
+     * generically is a good idea.
+     */
+    infof(data, "We got a 421 - timeout!\n");
+    state(conn, FTP_STOP);
     return CURLE_OPERATION_TIMEDOUT;
+  }
 
   return result;
 }
@@ -2394,6 +2401,7 @@ static CURLcode ftp_state_stor_resp(struct connectdata *conn,
 
   if(ftpcode>=400) {
     failf(data, "Failed FTP upload: %0d", ftpcode);
+    state(conn, FTP_STOP);
     /* oops, we never close the sockets! */
     return CURLE_UPLOAD_FAILED;
   }
@@ -2411,9 +2419,6 @@ static CURLcode ftp_state_stor_resp(struct connectdata *conn,
     if(!connected) {
       struct ftp_conn *ftpc = &conn->proto.ftpc;
       infof(data, "Data conn was not available immediately\n");
-      /* as there's not necessarily an immediate action on the control
-         connection now, we halt the state machine */
-      state(conn, FTP_STOP);
       ftpc->wait_data_conn = TRUE;
     }
 
@@ -3663,6 +3668,8 @@ static CURLcode ftp_do_more(struct connectdata *conn, bool *complete)
   /* the ftp struct is inited in ftp_connect() */
   struct FTP *ftp = data->state.proto.ftp;
 
+  *complete = FALSE;
+
   /* if the second connection isn't done yet, wait for it */
   if(!conn->bits.tcpconnect[SECONDARYSOCKET]) {
     result = Curl_is_connected(conn, SECONDARYSOCKET, &connected);
@@ -3675,6 +3682,18 @@ static CURLcode ftp_do_more(struct connectdata *conn, bool *complete)
       return result;
   }
 
+  if((data->state.used_interface == Curl_if_multi) &&
+     ftpc->state) {
+    /* multi interface and already in a state so skip the intial commands.
+       They are only done to kickstart the do_more state */
+    result = ftp_multi_statemach(conn, complete);
+
+    /* if we got an error or if we don't wait for a data connection return
+       immediately */
+    if(result || (ftpc->wait_data_conn != TRUE))
+      return result;
+  }
+
   if(ftp->transfer <= FTPTRANSFER_INFO) {
     /* a transfer is about to take place, or if not a file name was given
        so we'll do a SIZE on it later and then we need the right TYPE first */
@@ -3728,7 +3747,13 @@ static CURLcode ftp_do_more(struct connectdata *conn, bool *complete)
           return result;
       }
     }
-    result = ftp_easy_statemach(conn);
+    if(data->state.used_interface == Curl_if_multi) {
+      result = ftp_multi_statemach(conn, complete);
+
+      return result;
+    }
+    else
+      result = ftp_easy_statemach(conn);
   }
 
   if((result == CURLE_OK) && (ftp->transfer != FTPTRANSFER_BODY))
@@ -4402,20 +4427,21 @@ CURLcode ftp_parse_url_path(struct connectdata *conn)
 static CURLcode ftp_dophase_done(struct connectdata *conn,
                                  bool connected)
 {
-  CURLcode result = CURLE_OK;
   struct FTP *ftp = conn->data->state.proto.ftp;
   struct ftp_conn *ftpc = &conn->proto.ftpc;
 
   if(connected) {
     bool completed;
-    result = ftp_do_more(conn, &completed);
+    CURLcode result = ftp_do_more(conn, &completed);
-  }
 
-  if(result && (conn->sock[SECONDARYSOCKET] != CURL_SOCKET_BAD)) {
+    if(result) {
-    /* Failure detected, close the second socket if it was created already */
+      if(conn->sock[SECONDARYSOCKET] != CURL_SOCKET_BAD) {
-    Curl_closesocket(conn, conn->sock[SECONDARYSOCKET]);
+        /* close the second socket if it was created already */
-    conn->sock[SECONDARYSOCKET] = CURL_SOCKET_BAD;
+        Curl_closesocket(conn, conn->sock[SECONDARYSOCKET]);
-    return result;
+        conn->sock[SECONDARYSOCKET] = CURL_SOCKET_BAD;
+      }
+      return result;
+    }
   }
 
   if(ftp->transfer != FTPTRANSFER_BODY)
@@ -4427,7 +4453,7 @@ static CURLcode ftp_dophase_done(struct connectdata *conn,
 
   ftpc->ctl_valid = TRUE; /* seems good */
 
-  return result;
+  return CURLE_OK;
 }
 
 /* called from multi.c while DOing */

lib/pingpong.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2012, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -424,6 +424,9 @@ CURLcode Curl_pp_readresp(curl_socket_t sockfd,
            it may actually contain another end of response already! */
         clipamount = gotbytes - i;
         restart = TRUE;
+        DEBUGF(infof(data, "Curl_pp_readresp_ %d bytes of trailing "
+                     "server response left\n",
+                     (int)clipamount));
       }
       else if(keepon) {
 

tests/data/Makefile.am

@@ -93,7 +93,7 @@ test1379 test1380 test1381 test1382 test1383 test1384 test1385 test1386 \
 test1387 test1388 test1389 test1390 test1391 test1392 test1393 \
 test1400 test1401 test1402 test1403 test1404 test1405 test1406 test1407 \
 test1408 test1409 test1410 test1411 \
-test1500 \
+test1500 test1501 \
 test2000 test2001 test2002 test2003 test2004 test2005 test2006 test2007 \
 test2008 test2009 test2010 test2011 test2012 test2013 test2014 test2015 \
 test2016 test2017 test2018 test2019 test2020 test2021 test2022 \

tests/data/test1501

@@ -0,0 +1,53 @@
+<testcase>
+<info>
+<keywords>
+FTP
+RETR
+multi
+LIST
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data>
+</data>
+<servercmd>
+DELAY LIST 2
+DELAY TYPE 2
+</servercmd>
+</reply>
+
+# Client-side
+<client>
+<server>
+ftp
+</server>
+<tool>
+lib1501
+</tool>
+ <name>
+FTP with multi interface and slow LIST response 
+ </name>
+ <command>
+ftp://%HOSTIP:%FTPPORT/1501/
+</command>
+</client>
+# Verify data after the test has been "shot"
+<verify>
+<errorcode>
+0
+</errorcode>
+<protocol>
+USER anonymous
+PASS ftp@example.com
+PWD
+CWD 1501
+EPSV
+TYPE A
+LIST
+QUIT
+</protocol>
+
+</verify>
+</testcase>

tests/data/test591

@@ -63,8 +63,9 @@ TYPE I
 STOR 591
 QUIT
 </protocol>
+# CURLE_UPLOAD_FAILED = 25
 <errorcode>
-10
+25
 </errorcode>
 <upload>
 </upload>

tests/data/test592

@@ -52,6 +52,7 @@ Moooooooooooo for 592
 s/^PORT (.*)/PORT/
 s/^EPRT \|1\|(.*)/EPRT \|1\|/
 </strippart>
+# a 421 response must prevent further commands from being sent
 <protocol>
 USER anonymous
 PASS ftp@example.com
@@ -61,10 +62,10 @@ EPRT |1|
 PORT
 TYPE I
 STOR 592
-QUIT
 </protocol>
+# 28 == CURLE_OPERATION_TIMEDOUT
 <errorcode>
-10
+28
 </errorcode>
 <upload>
 </upload>

tests/libtest/.gitignore

@@ -1,5 +1,5 @@
 chkhostname
 lib5[0-9][0-9]
-lib1500
+lib150[0-9]
 libauthretry
 libntlmconnect

tests/libtest/Makefile.inc

@@ -20,7 +20,7 @@ noinst_PROGRAMS = chkhostname \
   lib556 lib539 lib557 lib560 lib562 lib564 lib565 lib566 lib567 lib568	\
   lib569 lib570 lib571 lib572 lib573 lib582 lib583 lib585 lib586 lib587 \
   lib590 lib591 lib597 lib598 lib599 libauthretry libntlmconnect \
-  lib1500
+  lib1500 lib1501
 
 chkhostname_SOURCES = chkhostname.c $(top_srcdir)/lib/curl_gethostname.c
 chkhostname_LDADD = @CURL_NETWORK_LIBS@
@@ -189,6 +189,8 @@ lib599_SOURCES = lib599.c $(SUPPORTFILES)
 
 lib1500_SOURCES = lib1500.c $(SUPPORTFILES) $(TESTUTIL)
 
+lib1501_SOURCES = lib1501.c $(SUPPORTFILES) $(TESTUTIL)
+
 libauthretry_SOURCES = libauthretry.c $(SUPPORTFILES)
 
 libntlmconnect_SOURCES = libntlmconnect.c $(SUPPORTFILES) $(TESTUTIL)

tests/libtest/lib1501.c

@@ -0,0 +1,126 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2012, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "test.h"
+
+#include <fcntl.h>
+
+#include "testutil.h"
+#include "warnless.h"
+#include "memdebug.h"
+
+#define TEST_HANG_TIMEOUT 30 * 1000
+
+/* 500 milliseconds allowed. An extreme number but lets be really conservative
+   to allow old and slow machines to run this test too */
+#define MAX_BLOCKED_TIME_US 500000
+
+/* return the number of microseconds between two time stamps */
+static int elapsed(struct timeval *before,
+                   struct timeval *after)
+{
+  ssize_t result;
+
+  result = (after->tv_sec - before->tv_sec) * 1000000 +
+    after->tv_usec - before->tv_usec;
+  if (result < 0)
+    result = 0;
+
+  return curlx_sztosi(result);
+}
+
+
+int test(char *URL)
+{
+  CURL *handle = NULL;
+  CURLM *mhandle = NULL;
+  int res = 0;
+  int still_running = 0;
+
+  start_test_timing();
+
+  global_init(CURL_GLOBAL_ALL);
+
+  easy_init(handle);
+
+  easy_setopt(handle, CURLOPT_URL, URL);
+  easy_setopt(handle, CURLOPT_VERBOSE, 1L);
+
+  multi_init(mhandle);
+
+  multi_add_handle(mhandle, handle);
+
+  multi_perform(mhandle, &still_running);
+
+  abort_on_test_timeout();
+
+  while(still_running) {
+    struct timeval timeout;
+    fd_set fdread;
+    fd_set fdwrite;
+    fd_set fdexcep;
+    int maxfd = -99;
+    struct timeval before;
+    struct timeval after;
+    int e;
+
+    timeout.tv_sec = 0;
+    timeout.tv_usec = 100000L; /* 100 ms */
+
+    FD_ZERO(&fdread);
+    FD_ZERO(&fdwrite);
+    FD_ZERO(&fdexcep);
+
+    multi_fdset(mhandle, &fdread, &fdwrite, &fdexcep, &maxfd);
+
+    /* At this point, maxfd is guaranteed to be greater or equal than -1. */
+
+    select_test(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
+
+    abort_on_test_timeout();
+
+    fprintf(stderr, "ping\n");
+    gettimeofday(&before, 0);
+
+    multi_perform(mhandle, &still_running);
+
+    abort_on_test_timeout();
+
+    gettimeofday(&after, 0);
+    e = elapsed(&before, &after);
+    fprintf(stderr, "pong = %d\n", e);
+
+    if(e > MAX_BLOCKED_TIME_US) {
+      res = 100;
+      break;
+    }
+  }
+
+test_cleanup:
+
+  /* undocumented cleanup sequence - type UA */
+
+  curl_multi_cleanup(mhandle);
+  curl_easy_cleanup(handle);
+  curl_global_cleanup();
+
+  return res;
+}