Re: [NSE] firewalk.nse updated

[David Fifield <david () bamsoftware com>]

On Wed, Sep 08, 2010 at 08:51:01PM +0200, Henri Doreau wrote:
> I've been working on adding UDP support to my initial firewalk.nse
> script. The path-mtu.nse script was a nice reference to achieve this.
> I've also rewritten function "definitions" to use the : "local
> function something(arg)" syntax instead of "local something =
> function(arg)". I find the former more readable. I can see both used
> in nmap scripts, so I assume there is no (or no big) difference
> between them.
>
> The script doesn't have an option to specify ports to scan yet.
> Currently, it selects every tcp-filtered and udp-open|filtered port.
>
> Please find attached this new version for review.

Thanks, I have committed it.

I want to suggest a different structure. Since you handle both TCP and
UDP, many of the functions have the same if/else structure:

        local function func(proto)
                if proto == IPPROTO_TCP then
                        ...
                elseif proto == IPPROTO_UDP then
                        ...
                end
        end

The problem here is that when someone adds a new protocol or makes a
change in one place, they have to remember to change or at least check
all the if/elses in the file. You can centralize the information better
using "protocol objects" that have a list of all their functions.

        tcp_funcs = {
                func = function()
                        ...
                end,
                -- More functions...
        }
        udp_funcs = {
                func = function()
                        ...
                end,
                -- More functions...
        }
        protos = {
                tcp = tcp_funcs,
                udp = udp_funcs,
        }

Then you would make calls like

        protos[proto].func()

And of course you can cache protos[proto] if the protocol stays the same
throughout the script execution.

David Fifield
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