From a620bba59fa086c6662391b6c029ce92f602cb3f Mon Sep 17 00:00:00 2001
From: Johan Wassberg <jocar@su.se>
Date: Fri, 23 Nov 2018 10:51:23 +0100
Subject: [PATCH] Handle servers that responds with a v2 packet to a v3
 request.

Hi NSClient++!
---
 lib/Nagios/NRPE/Client.pm | 56 ++++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 21 deletions(-)

diff --git a/lib/Nagios/NRPE/Client.pm b/lib/Nagios/NRPE/Client.pm
index b23a5cd..ce33a22 100644
--- a/lib/Nagios/NRPE/Client.pm
+++ b/lib/Nagios/NRPE/Client.pm
@@ -253,34 +253,48 @@ sub run
     }
     close($socket);
 
-    if (!$response)
+    if($response)
     {
-        $socket = $self->create_socket();
-        if (ref $socket eq "REF")
+        my $responsePacket = $packet->disassemble($response);
+        if ($responsePacket->{packet_version})
         {
-            return ($socket);
+            if ($responsePacket->{packet_version} == 3)
+            {
+                return $responsePacket;
+            }
         }
-        $packet   = Nagios::NRPE::Packet->new();
-        $response = undef;
-        $assembled = $packet->assemble(
-                                       type    => NRPE_PACKET_QUERY,
-                                       check   => $check,
-                                       version => NRPE_PACKET_VERSION_2
-                                      );
-
-        print $socket $assembled;
-        while (<$socket>)
+        else
         {
-            $response .= $_;
-        }
-        close($socket);
-
-        if (!$response)
-        {
-            my $reason = "No output from remote host";
+            my $reason = "Unknown response";
             return return_error($reason);
         }
     }
+
+    $socket = $self->create_socket();
+    if (ref $socket eq "REF")
+    {
+        return ($socket);
+    }
+    $packet   = Nagios::NRPE::Packet->new();
+    $response = undef;
+    $assembled = $packet->assemble(
+                                   type    => NRPE_PACKET_QUERY,
+                                   check   => $check,
+                                   version => NRPE_PACKET_VERSION_2
+                                  );
+
+    print $socket $assembled;
+    while (<$socket>)
+    {
+        $response .= $_;
+    }
+    close($socket);
+
+    if (!$response)
+    {
+        my $reason = "No output from remote host";
+        return return_error($reason);
+    }
     return $packet->disassemble($response);
 }