On Mon, Mar 22, 2021 at 10:47:09PM +0100, Toke Høiland-Jørgensen wrote: > Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx> writes: > > > Currently, if there are multiple xdpsock instances running on a single > > interface and in case one of the instances is terminated, the rest of > > them are left in an inoperable state due to the fact of unloaded XDP > > prog from interface. > > > > Consider the scenario below: > > > > // load xdp prog and xskmap and add entry to xskmap at idx 10 > > $ sudo ./xdpsock -i ens801f0 -t -q 10 > > > > // add entry to xskmap at idx 11 > > $ sudo ./xdpsock -i ens801f0 -t -q 11 > > > > terminate one of the processes and another one is unable to work due to > > the fact that the XDP prog was unloaded from interface. > > > > To address that, step away from setting bpf prog in favour of bpf_link. > > This means that refcounting of BPF resources will be done automatically > > by bpf_link itself. > > > > Provide backward compatibility by checking if underlying system is > > bpf_link capable. Do this by looking up/creating bpf_link on loopback > > device. If it failed in any way, stick with netlink-based XDP prog. > > Otherwise, use bpf_link-based logic. > > So how is the caller supposed to know which of the cases happened? > Presumably they need to do their own cleanup in that case? AFAICT you're > changing the code to always clobber the existing XDP program on detach > in the fallback case, which seems like a bit of an aggressive change? :) Sorry Toke, I was offline yesterday. Yeah once again I went too far and we shouldn't do: bpf_set_link_xdp_fd(xsk->ctx->ifindex, -1, 0); if xsk_lookup_bpf_maps(xsk) returned non-zero value which implies that the underlying prog is not AF_XDP related. closing prog_fd (and link_fd under the condition that system is bpf_link capable) is enough for that case. If we agree on that and there's nothing else that I missed, I'll send a v4. Thanks for review! > > -Toke >
