On Tue, Jun 09, 2026 at 02:02:01PM -0700, Stephen Hemminger wrote: > This is an RFC for an alternative way to capture packets from a DPDK > application. I did brief demo of similar mechanism at DPDK summit but > this is more complete. Capture runs in the primary process and is driven > entirely over telemetry; no secondary process is involved. > > A client asks the application to start capturing and passes it a file > descriptor to write to. The application writes pcapng to that descriptor. > A Wireshark extcap script is the intended front end, but the control path > is just telemetry and the output is just a pipe, so other front ends are > possible. > > 1/4 telemetry: let a command receive file descriptors from the client > 2/4 capture: the library > 3/4 test: functional test > 4/4 app: the Wireshark extcap script and its documentation > > Setup and usage are in doc/guides/tools/wireshark_extcap.rst. > > Primary process only for now; secondary-process capture is possible as > follow-on. Posting as RFC to get feedback on the approach. > > The extcap script is dual licensed (BSD-3-Clause OR GPL-2.0-or-later) as > it may be more useful in the Wireshark tree. >
One concern I have though - does this cause system-calls to be made in the fast-path because we are writting to a passed in FD? For performance reasons, would it not be better to use a memory buffer for this, thereby avoiding syscalls? For example, rather than passing in an FD to telemetry, we could pass in a key to be passed to shmget (going old-school!), or name parameter for shm_open. Thereafter with the memory buffer we can use a circular ring or similar to pass the data from app to client. /Bruce > Stephen Hemminger (4): > telemetry: allow commands to receive file descriptors > capture: infrastructure wireshark packet capture > test: add test for capture hooks > usertools/dpdk-wireshark-extcap.py: script for external capture > > MAINTAINERS | 4 + > app/test/meson.build | 1 + > app/test/test_capture.c | 365 +++++++++++ > doc/guides/rel_notes/release_26_07.rst | 12 + > doc/guides/tools/index.rst | 1 + > doc/guides/tools/wireshark_extcap.rst | 155 +++++ > lib/capture/capture.c | 821 +++++++++++++++++++++++++ > lib/capture/capture_impl.h | 56 ++ > lib/capture/filter.c | 108 ++++ > lib/capture/meson.build | 19 + > lib/meson.build | 1 + > lib/telemetry/rte_telemetry.h | 66 ++ > lib/telemetry/telemetry.c | 115 +++- > usertools/dpdk-wireshark-extcap.py | 274 +++++++++ > 14 files changed, 1986 insertions(+), 12 deletions(-) > create mode 100644 app/test/test_capture.c > create mode 100644 doc/guides/tools/wireshark_extcap.rst > create mode 100644 lib/capture/capture.c > create mode 100644 lib/capture/capture_impl.h > create mode 100644 lib/capture/filter.c > create mode 100644 lib/capture/meson.build > create mode 100755 usertools/dpdk-wireshark-extcap.py > > -- > 2.53.0 >
