libbpf deprecated methods for XDP

[salcock]

libbpf 0.7 has deprecated a whole bunch of XDP-related API methods -- these APIs are now implemented by libxdp (https://github.com/xdp-project/xdp-tools).

To account for this, we will need to:

• determine which version of libbpf we have at configure time
• if version >= 0.7, add libxdp as a build requirement and include the libxdp version of the XSK header
• otherwise, do what we currently do
• test that this works for all our various distros -- chances are there will be at least one case where the packaged libbpf is 0.7 but there is no packaged libxdp, for instance...

Ideally, by the time we get around to this, there will be examples of other projects who have dealt with this -- at the time of writing, this is not the case :(

Reference: https://lore.kernel.org/bpf/87mtms86e9.fsf@toke.dk/T/

[salcock]

Update: the deprecated APIs have now become removed APIs with the release of libbpf 1.0.

Best approach now is most likely:

• only support libbpf 1.0 and later, so we don't have to support multiple APIs
• figure out what the appropriate replacements are for the methods etc. that are no longer present
• implement and test the new replacements
• (longer term) think about building some libxdp and libbpf packages for Debian / Ubuntu so our packaged libtrace can support XDP

[salcock]

I think this is resolved now.