[xdp_traffic_count] - New basic ethhdr functions

[Dwctor]

Being able to translate benchmarks/xdp_traffic_count should be possible with a few basic changes. One of the most important is adding a few functions to our Honey library.

The first function should be able to get a pointer to the ethhdr struct of the "ctx" variable, represented by this section of code:

    void *end = (void *)(long)ctx->data_end;
    void *data = (void *)(long)ctx->data;
    struct ethhdr *eth = data;

And the second one should be able to get the h_source of it safely, like so:

    void *src = eth->h_source;
    if (src == 0)
      return XDP_PASS;
    if (src + 7 >= end)
      return XDP_PASS;

This code can be found in the benchmarks/xdp_traffic_count.

Both of these functions should be implemented in the lib/honey/translator.ex near the def to_c({{:., _, [Honey.Bpf_helpers, function]}, _, params}, context) do and def to_c({{:., _, [Honey.Bpf.Global, function]}, _, _params}, _context) do with a new namespace. I'll leave it up to the solver of the issue to name it, but an example could be Honey.ethhdr with functions get_pointer and get_hsource.

A few other issues might pop up, such as missing imports. That should be fixed in the lib/honey/boilerplates.ex file.

Anyone willing to help with this issue should make a pull request with the changes. I'll review them if I haven't solved it by then!

[Dwctor]

This is mostly done in the Type Propagation branch. I will close the issue once it's merged into main.