[Click] network load-balancer troubleshooting

[Sunjeet Singh]

> You can do something like this.
>
> my_switch[0] ->  Print(1) ->  ...
> my_switch[1] ->  Print(2) ->  ...
> my_switch[2] ->  Print(3) ->  ...
>

This doesn't print the packets that I am sending to eth4. Are the 
packets getting discarded before they are reaching Click? Or are they 
returning a value that is not in the my_switch[0] to my_switch[2] range?

> Also, you need to strip the original Ethernet header first.  Otherwise, you are
> just encapsulating an Ethernet frame inside another Ethernet frame.  So you
> would want to place a Strip(14) after my_switch[x].

I need to modify the MAC address fields (only) of the existing packets 
and send them. How should I go about doing that?

> My favorite debugging method is using a Tee.
>
> path ->  t :: Tee ->  ...
>
> t[1] ->  ToHostSniffers(ethX);
>
> and then you can just run tcpdump/wireshark to see what packets are on the path
> (assuming you have Ethernet packets).

I will look into this, thank you.


Thanks for your help!
Sunjeet


> Roman
>
>
> On Tue, 07 Dec 2010 14:38:28 -0800 Sunjeet Singh<sstattla at gmail.com>  wrote
>
>> Can someone please help me troubleshoot?
>>
>> On Linux, I'm trying to configure a load-balancer that sits in front of
>> a cluster, receives all packets destined to that cluster, calculates a
>> hash of some fields of the packet using HashSwitch() to decide which
>> worker machine in the cluster to send that packet to, and finally then
>> forwards that packet to that worker machine by rewriting the MAC Address
>> field of that packet.
>>
>> Here's what my click script looks like (currently testing with one
>> frontend machine and one worker machine)-
>>
>> AddressInfo(mymac<IP add. of frontend/8>  <mac add of eth0>);
>> AddressInfo(worker1<IP add. of worker1/8>  <mac add of worker eth0>);
>> AddressInfo(worker2<IP add. of worker1/8>  <mac add of eth1>);
>> AddressInfo(worker3<IP add. of worker1/8>  <mac add of eth2>);
>>
>> my_switch :: HashSwitch(26, 8);
>>
>> FromDevice(eth4, PROMISC true) ->  my_switch;
>> todevice1 :: ToDevice(eth0);
>> todevice2 :: ToDevice(eth1);
>> todevice3 :: ToDevice(eth2);
>>
>> my_switch[0] ->  EtherEncap(0x0800, mymac, worker1) ->  Queue ->  todevice1;
>> my_switch[1] ->  EtherEncap(0x0800, mymac, worker2) ->  Queue ->  todevice2;
>> my_switch[2] ->  EtherEncap(0x0800, mymac, worker3) ->  Queue ->  todevice3;
>>
>>
>> When I run the script with the command "sudo click try.click", it starts
>> executing and gives no messages. To test it,
>> I used tcpdump to first see if any of the interfaces on worker1 is
>> receiving any traffic ->  No.
>> Then I checked if any traffic is going out of eth0, eth1 or eth2 on
>> frontend ->  No.
>> Checked if eth4 is receiving the packets I sent through tcpreplay ->  Yes.
>>
>> How can I go about debugging this? I will greatly appreciate any help in
>> this regard.
>>
>> Thank you,
>> Sunjeet Singh
>>
>>
>> _______________________________________________
>> click mailing list
>> click at amsterdam.lcs.mit.edu
>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>
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