On Thu, Jun 04, 2020 at 10:40:06AM -0600, David Ahern wrote: > On 6/4/20 9:48 AM, Jesper Dangaard Brouer wrote: > > I will NOT send a patch that expose this in uapi/bpf.h. As I explained > > before, this caused the issues for my userspace application, that > > automatically picked-up struct bpf_devmap_val, and started to fail > > (with no code changes), because it needed minus-1 as input. I fear > > that this will cause more work for me later, when I have to helpout and > > support end-users on e.g. xdp-newbies list, as it will not be obvious > > to end-users why their programs map-insert start to fail. I have given > > up, so I will not NACK anyone sending such a patch. Jesper, you gave wrong direction to David during development of the patches and now the devmap uapi is suffering the consequences. > > > > Why is it we need to support file-descriptor zero as a valid > > file-descriptor for a bpf-prog? > > That was a nice property of using the id instead of fd. And the init to > -1 is not unique to this; adopters of the bpf_set_link_xdp_fd_opts for > example have to do the same. I think it's better to adopt "fd==0 -> invalid" approach. It won't be unique here. We're already using it in other places in bpf syscall. I agree with Jesper that requiring -1 init of 2nd field is quite ugly and inconvenient.
