libbpf: Fix compatibility for kernels without need_wakeup
When the need_wakeup flag was added to AF_XDP, the format of the XDP_MMAP_OFFSETS getsockopt was extended. Code was added to the kernel to take care of compatibility issues arrising from running applications using any of the two formats. However, libbpf was not extended to take care of the case when the application/libbpf uses the new format but the kernel only supports the old format. This patch adds support in libbpf for parsing the old format, before the need_wakeup flag was added, and emulating a set of static need_wakeup flags that will always work for the application. v2 -> v3: * Incorporated code improvements suggested by Jonathan Lemon v1 -> v2: * Rebased to bpf-next * Rewrote the code as the previous version made you blind Fixes: a4500432 ("libbpf: add support for need_wakeup flag in AF_XDP part") Reported-by: Eloy Degen <degeneloy@gmail.com> Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com> Link: https://lore.kernel.org/bpf/1571995035-21889-1-git-send-email-magnus.karlsson@intel.com
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