d1e91173cd
Add documentation for BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_DEVMAP_HASH including kernel version introduced, usage and examples. Add documentation that describes XDP_REDIRECT. Signed-off-by: Maryam Tahhan <mtahhan@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20221115144921.165483-1-mtahhan@redhat.com
82 lines
2.0 KiB
ReStructuredText
82 lines
2.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0-only
|
|
.. Copyright (C) 2022 Red Hat, Inc.
|
|
|
|
========
|
|
Redirect
|
|
========
|
|
XDP_REDIRECT
|
|
############
|
|
Supported maps
|
|
--------------
|
|
|
|
XDP_REDIRECT works with the following map types:
|
|
|
|
- ``BPF_MAP_TYPE_DEVMAP``
|
|
- ``BPF_MAP_TYPE_DEVMAP_HASH``
|
|
- ``BPF_MAP_TYPE_CPUMAP``
|
|
- ``BPF_MAP_TYPE_XSKMAP``
|
|
|
|
For more information on these maps, please see the specific map documentation.
|
|
|
|
Process
|
|
-------
|
|
|
|
.. kernel-doc:: net/core/filter.c
|
|
:doc: xdp redirect
|
|
|
|
.. note::
|
|
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
|
|
|
|
bpf_trace
|
|
^^^^^^^^^
|
|
The following bpftrace command can be used to capture and count all XDP tracepoints:
|
|
|
|
.. code-block:: none
|
|
|
|
sudo bpftrace -e 'tracepoint:xdp:* { @cnt[probe] = count(); }'
|
|
Attaching 12 probes...
|
|
^C
|
|
|
|
@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
|
|
|
|
.. note::
|
|
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:
|
|
|
|
.. code-block:: none
|
|
|
|
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:
|
|
|
|
.. code-block:: none
|
|
|
|
perf record -a -e xdp:xdp_redirect_err \
|
|
-e xdp:xdp_redirect_map_err \
|
|
-e xdp:xdp_exception \
|
|
-e xdp:xdp_devmap_xmit
|
|
|
|
References
|
|
===========
|
|
|
|
- https://github.com/xdp-project/xdp-tutorial/tree/master/tracing02-xdp-monitor
|