On 2025-03-14 10:21:15 [+0100], Toke Høiland-Jørgensen wrote:
> Hmm, how about putting the reset (essentially the changes you have
> above) into bpf_prog_run_xdp() itself, before executing the BPF program?
That would be the snippet below. It does work as far as the testcase
goes. It is just and unconditional write which might look like a waste
but given the circumstances…
While at it, is there anything that ensures that only bpf_prog_run_xdp()
can invoke the map_redirect callback? Mainline only assigns the task
pointer in NAPI callback so any usage outside of bpf_prog_run_xdp() will
lead to a segfault and I haven't seen a report yet so…
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -486,7 +486,12 @@ static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
* under local_bh_disable(), which provides the needed RCU protection
* for accessing map entries.
*/
- u32 act = __bpf_prog_run(prog, xdp, BPF_DISPATCHER_FUNC(xdp));
+ struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ u32 act;
+
+ ri->map_id = INT_MAX;
+ ri->map_type = BPF_MAP_TYPE_UNSPEC;
+ act = __bpf_prog_run(prog, xdp, BPF_DISPATCHER_FUNC(xdp));
if (static_branch_unlikely(&bpf_master_redirect_enabled_key)) {
if (act == XDP_TX && netif_is_bond_slave(xdp->rxq->dev))
--
2.47.2
> -Toke
Sebastian
