Fwd: [Click] ToDevice + ARP woes

[Eddie Kohler]

John Austen gave me permission to forward this...


Begin forwarded message:

> From: John Austen <deymious at yahoo.com>
> Date: November 28, 2004 1:27:35 PM PST
> To: Eddie Kohler <kohler at CS.UCLA.EDU>
> Subject: Re: [Click] ToDevice + ARP woes
>
> Yep, I'm also part of the Rutgers class. The
> assignment is now complete, but in the interest of
> advancing Click!...
>
> No, we didn't have the capability to alter the kernel
> code, in fact all the elements that would require a
> kernel recompile (like FromHost) were not available.
>
> Right up until the end I had very interesting behavior
> from ARP. The ARPResponder would have valid ARP
> requests sent to it, via a Classifier, but would not
> respond to the requests. Even more oddly, this did not
> stop me from getting the packets being sent to the
> Ethernet.
>
> After postponing the project deadline three times the
> assignment's goals were sharply reduced and the class
> handed in their projects as-is. One of the biggest
> problems was our infrastructure; the virtual machines
> needed to be tunneled to and these would go down
> relatively often. One other very large stumbling block
> I am sad to say was the Click! documentation. In many
> places it was startlingly incomplete. Since Click!
> does not have logical elements (if, then, variables)
> that allow the programmer to create their own logic,
> the programmer must be able to bulid their
> functionality out of the provided elements. To do this
> effectively very strong, careful, requirements for
> input and guarantees for output need to be made. I
> realize Click! is experimental and is indeed a work in
> progress, but it would benefit greatly from extended
> documentation. Two examples: the IPEncap element calls
> for an unsigned integer to determine what protocol to
> make the encapsulating packet, the example given in
> the documentation is 4, 'IP in IP', however nowhere do
> any other values appear. I had to troll through the
> source code in order to find the 79 other protocol
> specifiers. The FromSimDevice element has the
> following documentation to explain its function: 'This
> manual page describes the user-level version of the
> FromSimDevice element.'
>
> Unfortunately I had to make multiple trips through the
> source code, learn quite a bit about the gory details
> of Linux networking and its kernel, and run hosts of
> tests in order to determine the exact functionality of
> some elements... resulting twice in the crashing of
> the virutal machines we were working on, as well as
> almost two solid weeks of work in order to provide
> relatively simplistic functionality.
>
> The unit programming model certainly is attractive for
> cases like coding network devices, and I do realize
> Click! is not meant for wide-scale commercial release,
> but I believe that with greatly expanded documentation
> it would be much easier to use.
>
>
>
>
> 		
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