[Click] network load-balancer troubleshooting

[Roman Chertov]

You can do something like this.

my_switch[0] -> Print(1) -> ...
my_switch[1] -> Print(2) -> ...
my_switch[2] -> Print(3) -> ...

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].

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).

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
> 
> 
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