Re: [PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[David Ahern <dsahern@gmail.com>]

On 5/28/20 4:25 AM, Jesper Dangaard Brouer wrote:
> That said, you should use the new SEC(".maps") definitions, but you
> need to use some tricks to avoid a BTF-ID getting generated.  Let me
> help you with something that should work:
> 
> /* DEVMAP values */
> struct devmap_val {
> 	__u32 ifindex;   /* device index */
> };
> 
> struct {
> 	__uint(type, BPF_MAP_TYPE_DEVMAP);
> 	__uint(key_size, sizeof(u32));
> 	__uint(value_size, sizeof(struct devmap_val));
> 	__uint(max_entries, 4);
> } dm_ports SEC(".maps");
> 
> Notice by setting key_size and value_size, instead of the "__type",
> then a BTF-ID will be generated for this map.
> Normally with proper BTF it should look like:
> 
> struct {
> 	__uint(type, BPF_MAP_TYPE_DEVMAP);
> 	__type(key, u32);
> 	__type(value, struct devmap_val);
> 	__uint(max_entries, 4);
> } dm_ports_with_BTF SEC(".maps");
> 
> 

Thanks for the tip.