Re: payload file prototype

[David Fifield <david () bamsoftware com>]

On Thu, Feb 11, 2010 at 09:43:57PM -0500, Jay Fink wrote:
> On Wed, Feb 10, 2010 at 12:23 AM, David Fifield <david () bamsoftware com> wrote:
>
> > I was thinking to use an std::map<proto_port, Payload> for the global
> > list of payloads, where proto_port would be like
> >
> > struct proto_port {
> >        u8 proto;
> >        u16 port;
> > };
>
> Okay so that would be mapped into the global list or are you referring
> when were looking it up?

When looking it up. That's the key and the payload struct is the value.

> Right now, for the actual list itself, following is what I banged out
> last weekend. It is missing search and init but here is the header
> file for it, I trimmed out everything else, the functions listed
> (including constructor) work, some of them are just for practice at
> this point and might get tossed. My current test program initializes 3
> payloads inside the calling test itself. I am planning on using
> something similar to services to load up the file in the init portion.
> The next steps are load, then search (map):
>
> struct Payload {
>     char *proto; // number?
>     int dport; // dest port
>     char *data; // Payload data
>     int sport; // source port if we care
>     Payload* next; // next payload
> };
> class AllPayloads {
>     public:
>         AllPayloads();
>         ~AllPayloads();
>         int Count();
>         Payload* head;
>         int Add(Payload* Item);
>         Payload *Retrieve(int pos);
>         bool Find(Payload* Item);
>     private:
>         int size;
> };

I don't think you need to store the proto and dport for each payload;
the caller already has that information. You could do that if you needed
it for your data structure, but with a std::map you don't need that.

If you have a good idea for a data structure to use other than std::map,
that's cool. I just suggested it because this is exactly what it's
designed for, and it won't take a lot of extra work. You also wouldn't
need a special AllPayloads struct.

The worst part is just dealing with the C++ ugliness. Think of it in
pseudocode first. The algorithm will be something like this:

        loop:
                proto, ports, payload = parse_payload()
                for port in ports:
                        all_payloads[proto, port] = payload

Then lookup is just

        lookup(proto, port):
                return all_payloads[proto, port]

David Fifield
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