ftp_state_pasv_resp: connect through proxy also when set by env

When connecting back to an FTP server after having sent PASV/EPSV,
libcurl sometimes didn't use the proxy properly even though the proxy
was used for the initial connect.

The function wrongly checked for the CURLOPT_PROXY variable to be set,
which made it act wrongly if the proxy information was set with an
environment variable.

Added test case 711 to verify (based on 707 which uses --socks5). Also
added test712 to verify another variation of setting the proxy: with
--proxy socks5://

Bug: http://curl.haxx.se/bug/view.cgi?id=1218
Reported-by: Zekun Ni

lib/ftp.c

@@ -1951,13 +1951,11 @@ static CURLcode ftp_state_pasv_resp(struct connectdata *conn,
     return CURLE_FTP_WEIRD_PASV_REPLY;
   }
 
-  if(data->set.str[STRING_PROXY] && *data->set.str[STRING_PROXY]) {
+  if(conn->bits.proxy) {
     /*
-     * This is a tunnel through a http proxy and we need to connect to the
-     * proxy again here.
-     *
-     * We don't want to rely on a former host lookup that might've expired
-     * now, instead we remake the lookup here and now!
+     * This connection uses a proxy and we need to connect to the proxy again
+     * here. We don't want to rely on a former host lookup that might've
+     * expired now, instead we remake the lookup here and now!
      */
     rc = Curl_resolv(conn, conn->proxy.name, (int)conn->port, &addr);
     if(rc == CURLRESOLV_PENDING)

tests/data/Makefile.am

@@ -61,7 +61,7 @@ test626 test627 test628 test629 test630 test631 test632 test633 test634 \
 test635 test636 test637 test638 test639 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
-test709 test710 \
+test709 test710 test711 test712 \
 \
 test800 test801 test802 test803 test804 test805 test806 test807 test808 \
 \

tests/data/test711

+<testcase>
+#based off test 707 after bug report #1218
+<info>
+<keywords>
+FTP
+PASV
+RETR
+SOCKS5
+all_proxy
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+silly content
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+ftp
+socks5
+</server>
+<setenv>
+all_proxy=socks5://%HOSTIP:%SOCKSPORT 
+</setenv>
+ <name>
+FTP fetch with all_proxy set to socks5
+ </name>
+ <command>
+ftp://%HOSTIP:%FTPPORT/711
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+USER anonymous
+PASS ftp@example.com
+PWD
+EPSV
+TYPE I
+SIZE 711
+RETR 711
+QUIT
+</protocol>
+</verify>
+</testcase>

tests/data/test712

+<testcase>
+#based off test 707 after bug report #1218
+<info>
+<keywords>
+FTP
+PASV
+RETR
+SOCKS5
+all_proxy
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+silly content
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+ftp
+socks5
+</server>
+ <name>
+FTP fetch with --proxy set to socks5://
+ </name>
+ <command>
+ftp://%HOSTIP:%FTPPORT/712 --proxy socks5://%HOSTIP:%SOCKSPORT 
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+USER anonymous
+PASS ftp@example.com
+PWD
+EPSV
+TYPE I
+SIZE 712
+RETR 712
+QUIT
+</protocol>
+</verify>
+</testcase>