On Fri, 8 Aug 2025 09:55:38 -0700 Stephen Hemminger <step...@networkplumber.org> wrote:
> This is a rework of how packet capture is done in DPDK. > The existing mechanism using callbacks has a number of problems: > - can't work when packets are sent and received in secondary process > because callbacks only function in the primary process > - requires "opt-in" from application > > The new mechanism builds on the concept of port mirroring used > in Linux/FreeBSD and also router vendors (SPAN ports). > See: https://en.wikipedia.org/wiki/Port_mirroring for a general description. > > The implementation uses two new ethdev API's: > one to add a port mirror, and one to remove it. > > The internals of dumpcap are redone but the program command syntax is > unchanged (no doc change needed). Using the new mirror mechanism, the > dumpcap program creates a port using ring PMD and then directs a port > mirror to that new ring PMD instance. Then the packets are extracted > from the ring. If capturing on multiple devices, they all get > mirrored to the same ring PMD. > > The dumpcap program needs to be able to start the ring PMD it created > but the existing ethdev API is broken when used from secondary process. > One of the patches fixes that, it was also reported previously in Bugzilla. > > The mirror API is optimized to use lockless transmit if possible. > Fix the ring and null PMD to allow lockless transmit for use by capture. > > Added tests for the mirror features. > The performance has not been measured but the overhead of checking for > mirror port is no more that the overhead of looking at the callback list. > > v11 - fix build if BPF is disabled > - allow mirroring to device that is not lockfree > > Stephen Hemminger (14): > ethdev: allow start/stop from secondary process > ethdev: make sure all necessary headers included > ethdev: reorder bpf and ethdev dependency > bpf: add ability to load bpf into a buffer > test: add test for hotplug and secondary process operations > net/ring: allow lockfree transmit if ring supports it > net/ring: add new devarg to create vdev from existing ring > mbuf: add dynamic flag for use by port mirroring > ethdev: add port mirroring feature > app/testpmd: support for port mirroring > pcapng: split packet copy from header insertion > pcapng: make queue optional > app/dumpcap: use port mirror instead of pdump > doc: add documentation for port mirroring > > app/dumpcap/main.c | 392 +++++++++++--- > app/dumpcap/meson.build | 3 +- > app/test-pmd/cmdline.c | 13 + > app/test-pmd/cmdline_mirror.c | 194 +++++++ > app/test-pmd/cmdline_mirror.h | 13 + > app/test-pmd/meson.build | 1 + > app/test/meson.build | 9 +- > app/test/test_bpf.c | 28 + > app/test/test_ethdev_mirror.c | 325 ++++++++++++ > app/test/test_mp_secondary.c | 50 +- > config/rte_config.h | 1 + > doc/guides/prog_guide/bpf_lib.rst | 2 + > doc/guides/prog_guide/ethdev/index.rst | 1 + > doc/guides/prog_guide/ethdev/port_mirror.rst | 68 +++ > doc/guides/rel_notes/deprecation.rst | 5 + > doc/guides/rel_notes/release_25_11.rst | 5 + > doc/guides/testpmd_app_ug/testpmd_funcs.rst | 15 + > drivers/net/ring/rte_eth_ring.c | 49 ++ > lib/bpf/bpf_load.c | 111 +++- > lib/bpf/meson.build | 9 +- > lib/bpf/rte_bpf.h | 38 ++ > lib/{bpf/bpf_pkt.c => ethdev/ethdev_bpf.c} | 35 +- > lib/ethdev/ethdev_driver.c | 12 +- > lib/ethdev/ethdev_driver.h | 6 + > lib/ethdev/ethdev_private.c | 141 +++++ > lib/ethdev/ethdev_private.h | 29 ++ > lib/ethdev/ethdev_trace.h | 17 + > lib/ethdev/ethdev_trace_points.c | 6 + > lib/ethdev/meson.build | 8 + > lib/{bpf => ethdev}/rte_bpf_ethdev.h | 0 > lib/ethdev/rte_ethdev.c | 99 ++-- > lib/ethdev/rte_ethdev.h | 23 +- > lib/ethdev/rte_ethdev_core.h | 12 +- > lib/ethdev/rte_mirror.c | 508 +++++++++++++++++++ > lib/ethdev/rte_mirror.h | 147 ++++++ > lib/mbuf/rte_mbuf_dyn.h | 9 + > lib/meson.build | 4 +- > lib/pcapng/rte_pcapng.c | 179 ++++--- > lib/pcapng/rte_pcapng.h | 27 +- > 39 files changed, 2342 insertions(+), 252 deletions(-) > create mode 100644 app/test-pmd/cmdline_mirror.c > create mode 100644 app/test-pmd/cmdline_mirror.h > create mode 100644 app/test/test_ethdev_mirror.c > create mode 100644 doc/guides/prog_guide/ethdev/port_mirror.rst > rename lib/{bpf/bpf_pkt.c => ethdev/ethdev_bpf.c} (95%) > rename lib/{bpf => ethdev}/rte_bpf_ethdev.h (100%) > create mode 100644 lib/ethdev/rte_mirror.c > create mode 100644 lib/ethdev/rte_mirror.h > FYI - this set still has a couple of issues. - the secondary process doing packet transfer still is not captured - the introduction of another field in fast path causes cache misses Looking into whether pdump can just broadcast to secondaries instead like hotplug does. This is less impactful change. Then if pdump can work unchanged, can make a port mirror demo application using existing infrastructure and callbacks.
