Supported maps

XDP_REDIRECT works with the following map types:





For more information on these maps, please see the specific map documentation.


XDP_REDIRECT works by a three-step process, implemented in the functions below:

  1. The bpf_redirect() and bpf_redirect_map() helpers will lookup the target of the redirect and store it (along with some other metadata) in a per-CPU struct bpf_redirect_info.

  2. When the program returns the XDP_REDIRECT return code, the driver will call xdp_do_redirect() which will use the information in struct bpf_redirect_info to actually enqueue the frame into a map type-specific bulk queue structure.

  3. Before exiting its NAPI poll loop, the driver will call xdp_do_flush(), which will flush all the different bulk queues, thus completing the redirect. Note that xdp_do_flush() must be called before napi_complete_done() in the driver, as the XDP_REDIRECT logic relies on being inside a single NAPI instance through to the xdp_do_flush() call for RCU protection of all in-kernel data structures.


Not all drivers support transmitting frames after a redirect, and for those that do, not all of them support non-linear frames. Non-linear xdp bufs/frames are bufs/frames that contain more than one fragment.

Debugging packet drops

Silent packet drops for XDP_REDIRECT can be debugged using:

  • bpf_trace

  • perf_record


The following bpftrace command can be used to capture and count all XDP tracepoints:

sudo bpftrace -e 'tracepoint:xdp:* { @cnt[probe] = count(); }'
Attaching 12 probes...

@cnt[tracepoint:xdp:mem_connect]: 18
@cnt[tracepoint:xdp:mem_disconnect]: 18
@cnt[tracepoint:xdp:xdp_exception]: 19605
@cnt[tracepoint:xdp:xdp_devmap_xmit]: 1393604
@cnt[tracepoint:xdp:xdp_redirect]: 22292200


The various xdp tracepoints can be found in source/include/trace/events/xdp.h

The following bpftrace command can be used to extract the ERRNO being returned as part of the err parameter:

sudo bpftrace -e \
'tracepoint:xdp:xdp_redirect*_err {@redir_errno[-args->err] = count();}
tracepoint:xdp:xdp_devmap_xmit {@devmap_errno[-args->err] = count();}'

perf record

The perf tool also supports recording tracepoints:

perf record -a -e xdp:xdp_redirect_err \
    -e xdp:xdp_redirect_map_err \
    -e xdp:xdp_exception \
    -e xdp:xdp_devmap_xmit