Don't use the ALLO command on FTP servers that don't support it

Despite always having been present in the FTP specification, some servers
(e.g. Enterprise FTP server (version 6600)) do not support the ALLO
command. Do not use the command on such servers otherwise its failure will
cause the PUT command which normally follows it to fail (since the success
of the ALLO command is now checked, as of commit 0d616e68cc).

Fixes CPAN RT#95717, also reported by an Enterprise FTP server user.

2 files changed, 6 insertions, 2 deletions

diff --git a/Changes b/Changes
index 1d5a19d..b65075a 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,7 @@
 libnet 1.28  -- TODO
 
+  * Don't use the ALLO command on FTP servers that don't support it.  [Resolves
+    CPAN RT#95717]
   * Stop Makefile.PL from requiring interactive configuration when running via
     cpan, cpanp or cpanm: just accept all defaults in these cases, as when
     running non-interactively.  [Resolves CPAN RT#48966]
diff --git a/lib/Net/FTP.pm b/lib/Net/FTP.pm
index eb8e7dc..e8b2d95 100644
--- a/lib/Net/FTP.pm
+++ b/lib/Net/FTP.pm
@@ -490,7 +490,7 @@ sub alloc {
     unless (defined $size);
 
   return
-    unless ($ftp->_ALLO($size, @_));
+    unless ($ftp->supported("ALLO") and $ftp->_ALLO($size, @_));
 
   ${*$ftp}{'net_ftp_allo'} = join(" ", $size, @_);
 
@@ -1148,7 +1148,9 @@ sub _data_cmd {
   return
     unless $ok;
 
-  if ($cmd =~ /(STOR|APPE|STOU)/ and exists ${*$ftp}{net_ftp_allo}) {
+  if ($cmd =~ /(STOR|APPE|STOU)/ and exists ${*$ftp}{net_ftp_allo} and
+      $ftp->supported("ALLO"))
+  {
     $ftp->_ALLO(delete ${*$ftp}{net_ftp_allo})
       or return;
   }