[Click] strange Queue behaviour

[Peter De Cleyn]

Hi all,

While debugging a larger configuration used in userspace, which
occasionally reported errors when sending packets (packets were
returned on output 1 of ToDevice whithout further indication of an
error), I wrote myself the following simple testconfiguration.

out::Queue()->ToDevice(eth1)->Print("Error on send")->Discard;
arpq::ARPQuerier(192.168.0.1, 00:0E:0C:37:BF:36);

FromDevice("eth1")->class::Classifier(12/0806 20/0001, //arp request
                        12/0806 20/0002, //arp response
                        12/0800, //ip
                        -); //other

class[0]->ARPResponder(192.168.0.1 00:0E:0C:37:BF:36)
        ->out;

class[1]->[1]arpq->out;

class[2]->CheckIPHeader(14)->IPPrint("incoming")->Discard();

class[3]->Print("Discard")->Discard();

ICMPPingSource(192.168.0.1, 192.168.0.2, INTERVAL 1)
        ->arpq; 

I expected some basic ping behaviour, but the only output I got on screen was:

Error on send:   42 | ffffffff ffff000e 0c37bf36 08060001 08000604 0001000e
Error on send:   42 | ffffffff ffff000e 0c37bf36 08060001 08000604 0001000e
...

Which are actually the ARP requests one would expect to be sent before
the ICMP messages could be sent.

When I omitted the Queue from the configuration, everything worked fine.
thus the first line of the configuration became:

out::ToDevice(eth1)->Print("Error on send")->Discard;

As the ToDevice did not provided extra output ( looking into the code
of ToDevice, I expected some messages), I added my own debug output at
the beginning of send_packet() and push() and noticed that this was
printed when I didn't use the Queue, but they didn't appear when using
it. I tried with Queue, SimpleQueue and MSQueue and click versions
1.4.1, 1.4pre1 and 1.3pre1. The configuration was also tested with
different machines, using different types of NICs.

Could someone point me out what I am missing here?

thanks a lot for helping me out!

Peter