On Fri, 27 Mar 2026 14:42:19 +0800 Leon Hwang wrote: > > It may be worth adding a selftest to > > tools/testing/selftests/drivers/net/xdp.py > > which sets MTU to 9k, tries to attach a non-frag-capable prog > > if that fails attaches a frag-capable prog and then checks if > > replacing the capable prog with non-capable fails. > > Drivers may be buggy in this regard. > > Do you mean adding these two tests to xdp.py? > > 1. Verify the failure of attaching non-frag-capable prog to mtu=9k > driver. > 2. Verify the failure of updating frag-capable prog with non-frag- > capable prog via libbpf.c::bpf_link__update_program().
Not directly via libbpf just ip -f link, it uses libbpf internally but testing with ip link is simpler. Also - there are already XDP progs which return XDP_PASS in frag-capable and non-capable mode, so just use those. > As for test #2, it may require a helper to attach prog then update prog > using libbpf's APIs. See above.
