[Click] testbed setup using click

[Beyers Cronje]

A couple of notes from me.

1) I would use FromDevice(ethX, SNIFFER false), this ensures Linux kernel
does not also handle the packets. See
http://read.cs.ucla.edu/click/elements/fromdevice.u
2) Is your MyElementModify element recalculating IP and TCP/UDP checksums?
3) When you work with IP packets, ALWAYS put in a  Classifier(12/0800, -)
just after FromDevice to ensure you are not inadvertently working on non-IP
packets like ARP etc.
4) Node B requires MarkIPHeader/CheckIPHeader before IPPrint.

Cant really comment any more without seeing how you modify the packet
contents inside MyElementModify

On Wed, Oct 6, 2010 at 11:56 AM, Ashok Anand <aa2jaiswal at gmail.com> wrote:

> I see. so the environment is emulab,
>
> the path is setup between, webserver to nodeA to nodeB to client
> and for nodeA, click configuration looks like,
>
> FromDevice(eth6)
>       -> Strip(14)
>       -> CheckIPHeader(0, CHECKSUM true, VERBOSE true)
>       -> Print('Ok')
>       -> IPPrint(LENGTH true)
>       -> MyElementModify()
>       -> CheckIPHeader(0, CHECKSUM true, VERBOSE true)
>       -> Unstrip(14)
>       -> Queue(10)
>       -> ToDevice(eth8)
>
> and nodeB looks like,
>
> FromDevice(eth7)
>       -> Strip(14)
>       -> IPPrint(LENGTH true)
>        -> MyElementUnModify()
>       -> Unstrip(14)
>       -> Queue(10)
>       -> ToDevice(eth9)
>
> these interfaces are correct interfaces in the path.
>
>
>
>
> On Wed, Oct 6, 2010 at 4:19 AM, Beyers Cronje <bcronje at gmail.com> wrote:
>
>> Hi,
>>
>> You can modify packet data in userlevel Click, so that is not the problem.
>> Maybe post an example of how you are changing the packet.
>>
>> On Wed, Oct 6, 2010 at 9:59 AM, Ashok Anand <aa2jaiswal at gmail.com> wrote:
>>
>> > Hi,
>> >
>> > I am a new user to click.
>> > I am trying to setup a simple testbed using click.
>> > so there is a web server and a client, and there are two intermediate
>> > nodes,
>> > which runs click at userlevel.
>> > First intermediate node, changes packet data, while second intermediate
>> > undo
>> > the changes.
>> >
>> > The problem that I am facing is that, the second intermediate node does
>> not
>> > find any changes in the packet.
>> > Is it because, the click is running at userlevel, and modification at
>> > userlevel, does not appear when sent to network..
>> > (I am using simple configuration, which just reads packet from an
>> > interface,
>> > changes it, and then sends to another interface).
>> >
>> > Please let me know.
>> >
>> > Thanks,
>> > Ashish
>> > _______________________________________________
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>> > click at amsterdam.lcs.mit.edu
>> > https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>> >
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>
>