On 7/13/24 23:23, Adrian Moreno wrote:
> (Was: Add psample support to NXAST_SAMPLE action)
>
> This is the userspace counterpart of the work done in the kernel
> which has recently been merged in net-next [1]. There, a new
> datapath action is added, called "psample".
>
> From the PoV of ovs-vswitchd, this new action is used to implement
> "local sampling". Local sampling (or lsample for short) is configured
> in a similar way as current per-flow IPFIX sampling, i.e: using the
> Flow_Sample_Collector_Set table and the NXAST_SAMPLE action.
>
> However, instead of sending the sample to an external IPFIX collector
> though the network, the sample is emitted using the new action and
> made available to locally running sample collector.
>
> The specific way emit_sample sends the sample (and the way the local
> collector shall collect it) is datapath-specific.
> Currently, currently only the Linux kernel datapath implements it using
> the psample netlink multicast group.
>
> ~~ Configuration ~~
> Local sampling is configured via a new column in the
> Flow_Sample_Collector_Set (FSCS) table called "local_group_id".
> Configuring this value is orthogonal to also associating the FSCS
> entry to an entry in the IPFIX table.
>
> Once that entry in the OVSDB is configured, NXAST_SAMPLE actions coming
> from the controller will be translated into the following odp action:
>
> sample(sample={P}%, actions(emit_sample(group={G},cookie={C})))
>
> Where:
> P: Is the sampling probability from NXAST_SAMPLE
> G: Is the group id in the FSCS entry whose "id" matches the one in
> the NXAST_SAMPLE.
> C: Is a 64bit cookie result of concatenating the obs_domain and
> obs_point from the NXAST_SAMPLE in network order, i.e:
> "htonl(obs_domain) << 32 | htonl(obs_point)"
> Notes:
> - The parent sample action might be omitted if the probability is
> 100% and there is no IPFIX sampling that requires the use of a
> meter.
>
> ~~ Dpif-lsample ~~
> Internally, a new object called "dpif-lsample" is introduced to track
> the configured local sampling exporters and track statistics based on
> odp flow stats (using xcache).
> It exposes the list of configured exporters and their statistics on a
> new unixctl command called "lsample/show".
>
> ~~ Drop monitoring ~~
> A common use-case for this action can be to sample drops. However,
> adding sample actions to drops makes the existing drop statistics
> disappear. In order to fix this, patch 11 make use of explicit
> drop actions to ensure statistics still report drops even if sampled.
> /home/amorenoz/devel/patches/ovs/ovs_psample/v2/v2-0000-cover-letter.patch
> ~~ Extended OpenFlow sample action ~~
> Given the series aims at making sampling production ready, conntrack
> integration must be considered. A common use-case for state-full
> pipelines is to calculate the observation metadata at connection
> establishment, store it in ct_label and then use it for packets of
> established connections. However, this forces OVN to create a big number
> of OFP Flows (one per distinct cookie). Patch 13 solves this by allowing
> controllers to specify the obs_domain and point ids from another OFP
> field.
>
> ~~ Testing ~~
> The series includes an test utility program than can be executed by
> running "tests/ovstest test-psample". This utility listens
> to packets multicasted by the psample module and prints them (also
> printing the obs_domain and obs_point ids).
>
> ~~ HW Offload ~~
> tc offload is not being introduced in this series as existing sample
> or userspace actions are not currently offloadable. Also some
> improvements need to be implemented in tc for it to be feasible.
>
> ~~ DPDK datapath ~~
DPDK is not a datapath. :)
> By naming the action "psample" it was intentionally restricted to the
> Linux datapath only. A follow up task would be spawned to think of a
> good way of implementing local-sampling in the userspace datapath.
>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=aae0b82b46cb5004bdf82a000c004d69a0885c33
>
> ---
> * v3 -> v4
> - Dropped patches 7 and 8 that added a unixctl command to gather
> statistics as they would be inaccurate and of low added value.
> - Addressed other small comments from Ilya.
>
> * v2 -> v3
> - Added a knob to configure explicit sampled drops.
> - Addressed Eelco comments.
>
> * v1 -> v2
> - Added a patch (12/13) that implements Eelco's suggestion of adding
> a global constant all-one "enum mf_subfield"
> - Combined both drop-monitoring patches into one that is implemented by
> tweaking the odp actions list if it ends with a sample action.
> - Added a test case that includes non-100% probability for which
> test-psample.c is tought to also print it.
> - Support specifying smaller fields in obs_{point/domain}_id.
> - Address other styling comments from Eelco and Ilya.
>
> * rfc_v2 -> rfc_v3
> - Added patches 11, 12 and 13 fixing drop monitoring and extending the
> OpenFlow action to support field-specifiers.
>
>
> Adrian Moreno (11):
> ofproto-dpif: Allow forcing dp features.
> odp-util: Add support OVS_ACTION_ATTR_PSAMPLE.
> ofproto_dpif: Check for psample support.
> ofproto: Add ofproto-dpif-lsample.
> vswitchd: Add local sampling to vswitchd schema.
> ofproto-dpif-xlate: Use psample for local sample.
> tests: Add test-psample testing utility.
> tests: Test local sampling.
> ofproto: xlate: Make sampled drops explicit.
> ofproto-dpif-xlate: Avoid allocating mf_subfield.
> ofp-actions: Load data from fields in sample action.
>
> Documentation/ref/ovs-actions.7.rst | 15 +-
> NEWS | 12 +
> include/linux/automake.mk | 1 +
> include/linux/openvswitch.h | 28 ++
> include/linux/psample.h | 68 +++++
> include/openvswitch/meta-flow.h | 3 +
> include/openvswitch/ofp-actions.h | 8 +-
> lib/dpif-netdev.c | 1 +
> lib/dpif.c | 10 +-
> lib/dpif.h | 1 +
> lib/meta-flow.c | 2 +
> lib/odp-execute.c | 25 +-
> lib/odp-util.c | 91 +++++++
> lib/odp-util.h | 3 +
> lib/ofp-actions.c | 245 ++++++++++++++++--
> ofproto/automake.mk | 2 +
> ofproto/ofproto-dpif-ipfix.c | 1 +
> ofproto/ofproto-dpif-lsample.c | 199 ++++++++++++++
> ofproto/ofproto-dpif-lsample.h | 40 +++
> ofproto/ofproto-dpif-sflow.c | 1 +
> ofproto/ofproto-dpif-xlate.c | 354 +++++++++++++++++--------
> ofproto/ofproto-dpif-xlate.h | 9 +-
> ofproto/ofproto-dpif.c | 124 ++++++++-
> ofproto/ofproto-dpif.h | 9 +-
> ofproto/ofproto-provider.h | 13 +
> ofproto/ofproto.c | 21 ++
> ofproto/ofproto.h | 10 +
> python/ovs/flow/odp.py | 8 +
> python/ovs/flow/ofp.py | 8 +-
> python/ovs/flow/ofp_act.py | 6 +-
> tests/automake.mk | 3 +-
> tests/drop-stats.at | 168 ++++++++++++
> tests/odp.at | 16 ++
> tests/ofp-actions.at | 8 +
> tests/ofproto-dpif.at | 263 +++++++++++++++++++
> tests/ovs-ofctl.at | 14 +
> tests/system-common-macros.at | 4 +
> tests/system-traffic.at | 385 ++++++++++++++++++++++++++++
> tests/test-psample.c | 288 +++++++++++++++++++++
> vswitchd/bridge.c | 82 +++++-
> vswitchd/vswitch.ovsschema | 9 +-
> vswitchd/vswitch.xml | 70 ++++-
> 42 files changed, 2462 insertions(+), 166 deletions(-)
> create mode 100644 include/linux/psample.h
> create mode 100644 ofproto/ofproto-dpif-lsample.c
> create mode 100644 ofproto/ofproto-dpif-lsample.h
> create mode 100644 tests/test-psample.c
>
Thanks, Adrian! I fixed a few small style issues and applied the set.
Best regards, Ilya Maximets.
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