Re: XDP BPF Stack Limit Issues

Thank you for pointing this out Jesper! I'm honestly surprised I didn't 
realize this before.


I've made this change and I'm able to compile the XDP/BPF program 
without any issues now.


Thank you again!

On 12/17/2020 2:50 AM, Jesper Dangaard Brouer wrote:
> I have to look elsewhere[2] to see that:
>   #define MAX_FILTERS 55
>
> Your problem is that you create an array with 55 pointers each 8 bytes
> equal 440 bytes on the stack (max stack is 512).  Why do you need to
> lookup all 55 map elements in a loop before using them?
>
> https://gist.github.com/gamemann/663674924e16286b02a835637912c2a5#file-xdp_fw_ipv6_maps-c-L267
>
>   struct filter *filter[MAX_FILTERS];
>   for (uint8_t i = 0; i < MAX_FILTERS; i++)
>      {
>          key = i;
>          
>          filter[i] = bpf_map_lookup_elem(&filters_map, &key);
>      }
>   [...]
>   for (uint8_t i = 0; i < MAX_FILTERS; i++)
>      {
>          // Check if ID is above 0 (if 0, it's an invalid rule).
>          if (!filter[i] || filter[i]->id < 1)
>    [...]