[switchorch][mirrororch]: Add sampled port mirroring with truncation support by Janetxxx · Pull Request #4502 · sonic-net/sonic-swss

Janetxxx · 2026-04-21T12:25:29Z

What I did
Adds sampled port mirroring with packet truncation support. This PR targets and validates the ERSPAN use case, which is the primary motivation for the feature in the HLD (sonic-net/SONiC#2296).

SwitchOrch — capability discovery

During init, queries SAI via sai_query_attribute_capability() and publishes to STATE_DB under SWITCH_CAPABILITY|switch:

PORT_INGRESS_SAMPLE_MIRROR_CAPABLE (SAI_PORT_ATTR_INGRESS_SAMPLE_MIRROR_SESSION)
PORT_EGRESS_SAMPLE_MIRROR_CAPABLE (SAI_PORT_ATTR_EGRESS_SAMPLE_MIRROR_SESSION)
SAMPLEPACKET_TRUNCATION_CAPABLE (SAI_SAMPLEPACKET_ATTR_TRUNCATE_ENABLE)

MirrorOrch — SamplePacket lifecycle

Creates/binds a single SAMPLEPACKET object when sample_rate is set. Direction-aware binding: RX uses INGRESS_SAMPLEPACKET_ENABLE + INGRESS_SAMPLE_MIRROR_SESSION, TX uses the EGRESS_* equivalents, and BOTH binds ingress and egress with one SAMPLEPACKET.
Truncation implies sampling: truncate_size without an explicit sample_rate defaults the rate to 1 (sample every packet).
Capability gating: rejects the session when the required per-direction sampled mirroring (ingress/egress) is not supported; skips truncation if unsupported.
Session update is delete-and-recreate only; in-place SET on an existing key is treated as a duplicate and ignored.
Cross-feature guard with sFlow: get-before-set on INGRESS_SAMPLEPACKET_ENABLE prevents silent overwrite.

SflowOrch

sflowAddPort() / sflowUpdateSampleDirection()check INGRESS/EGRESS_SAMPLEPACKET_ENABLE before binding and reject if the port's samplepacket slot is already owned by a non-sFlow feature

Why I did it
This is part of the sampled port mirroring with truncation feature. It enables per-port hardware-based sampling on ERSPAN mirror sessions, reducing mirror bandwidth by only mirroring 1 out of every N packets with optional packet truncation.

How I verified it

Unit (mock) tests

switchorch_ut.cpp, mirrororch_ut.cpp:

Capability fields written to STATE_DB
Sampled vs full mirror path selection
SAMPLEPACKET create/remove, MirrorEntry defaults
Per-direction capability gating; rejection when ingress/egress sampled mirroring or truncation is unsupported (booleans toggled directly, which a VS test cannot do)
Input validation, non-existent session handling, fault-injection on SAMPLEPACKET create/remove

VS integration tests

SAMPLEPACKET lifecycle + port attribute binding/cleanup, truncation attrs
RX, TX (egress) and BOTH direction binding
truncate_size without sample_rate defaults to sample_rate=1
Delete-and-recreate updates a session; duplicate SET on an existing key is ignored (no SAI/STATE_DB mutation)
Route lifecycle: session stays unprogrammed while inactive, and is torn down / reprogrammed across route withdrawal and restore
Backward compat: no SAMPLEPACKET created when sample_rate absent
STATE_DB field verification, switch capability values, multi-port binding, LAG members, sFlow conflict rejection

Details if related

mssonicbld · 2026-04-21T12:25:38Z

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azure-pipelines · 2026-04-21T12:25:48Z

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Pull request overview

Adds SwitchOrch startup capability discovery for sampled port mirroring and samplepacket truncation, publishing results into SWITCH_CAPABILITY|switch for consumption by other components (e.g., MirrorOrch/CLI) to enable runtime feature gating.

Changes:

Introduces new capability keys for ingress/egress sampled mirror and samplepacket truncation in switchorch.h.
Adds SwitchOrch::querySwitchSampledMirrorCapability() to query SAI attribute capabilities and store results in STATE_DB.
Exposes new SwitchOrch getters for sampled mirror and truncation support flags.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
orchagent/switchorch.h	Adds new capability key macros, new public support getters, and a private query method declaration.
orchagent/switchorch.cpp	Calls the new query at startup and implements SAI capability discovery + STATE_DB publishing.

mssonicbld · 2026-04-24T10:35:57Z

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…ed ERSPAN route/session/sFlow/samplepacket state before and after every test Signed-off-by: Janet Cui <janet970527@gmail.com>

mssonicbld · 2026-06-06T04:58:59Z

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…p rollback Signed-off-by: Janet Cui <janet970527@gmail.com>

mssonicbld · 2026-06-17T01:23:28Z

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bingwang-ms · 2026-06-17T15:36:35Z

Discussed and addressed comments offline. Approving the PR

prsunny · 2026-06-18T00:36:22Z

@Janetxxx , this is pretty big for 202605 backport. Wouldn't prefer a CP - @r12f , @vaibhavhd , @yxieca for viz

prsunny · 2026-06-18T00:45:18Z

@Janetxxx , would you asses the PR for cherry-pick?

No backward compatibility issues
Are these changes enabled under a specific configuration?

Janetxxx · 2026-06-19T04:17:40Z

Thanks for your comment @prsunny, I manually built an image with this PR included and ran the existing port mirroring tests span/test_port_mirroring.py on a SN5640 T0 testbed to verify that it didn't cause any backward compatibility issues.

Janetxxx · 2026-06-19T04:30:58Z

@prsunny 2. Yes, these changes are opt-in. Sampled mirroring only activates when users specify sample_rate or truncate_size in the mirror session. Existing sessions without these optional fields continue to work as full mirrors, no behavior change.

Janetxxx · 2026-06-30T05:14:04Z

Manually cherry-picked into 202607 Azure/sonic-swss.msft#254

Copilot AI review requested due to automatic review settings April 21, 2026 12:25

Janetxxx requested a review from prsunny as a code owner April 21, 2026 12:25

Copilot started reviewing on behalf of Janetxxx April 21, 2026 12:26 View session

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Comment thread orchagent/switchorch.h Outdated

Comment thread orchagent/switchorch.h Outdated

Comment thread orchagent/switchorch.cpp

Janetxxx force-pushed the dev/jc/sampled-port-mirror-capability branch from 5d5de0a to 3f09e7a Compare April 24, 2026 10:45

Janetxxx force-pushed the dev/jc/sampled-port-mirror-capability branch from 3f09e7a to 239ac81 Compare April 24, 2026 10:54

Janetxxx force-pushed the dev/jc/sampled-port-mirror-capability branch from e839e2e to ae43ab0 Compare April 24, 2026 11:01

Janetxxx force-pushed the dev/jc/sampled-port-mirror-capability branch from ae43ab0 to 06b869a Compare April 28, 2026 08:34

Janetxxx requested a review from r12f April 28, 2026 08:35

Janetxxx changed the title ~~[switchorch]: Add sampled mirror and truncation capability discovery~~ [switchorch]: Add sampled port mirror and truncation capability discovery Apr 28, 2026

Janetxxx mentioned this pull request Apr 29, 2026

[orchagent][MirrorOrch] Add sampled port mirroring support to MirrorOrch #4488

Closed

Janetxxx force-pushed the dev/jc/sampled-port-mirror-capability branch from 06b869a to 427887c Compare April 29, 2026 08:07

Janetxxx changed the title ~~[switchorch]: Add sampled port mirror and truncation capability discovery~~ [switchorch][mirrororch]: Add sampled port mirroring with truncation support Apr 29, 2026

Janetxxx mentioned this pull request May 1, 2026

[HLD]: adds the High-Level Design document for Sampled Port Mirroring with Truncation sonic-net/SONiC#2296

Merged

[VS test] Add an autouse isolation fixture that force-cleans the shar…

8e2332f

…ed ERSPAN route/session/sFlow/samplepacket state before and after every test Signed-off-by: Janet Cui <janet970527@gmail.com>

Pterosaur previously approved these changes Jun 9, 2026

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kperumalbfn reviewed Jun 11, 2026

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Comment thread orchagent/mirrororch.cpp

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Comment thread orchagent/switchorch.cpp

bingwang-ms reviewed Jun 16, 2026

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Comment thread orchagent/sfloworch.cpp

[sfloworch]: Refactor sflowAddPort to remove duplicated logic and dro…

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…p rollback Signed-off-by: Janet Cui <janet970527@gmail.com>

Pterosaur approved these changes Jun 17, 2026

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Janetxxx commented Apr 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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SwitchOrch — capability discovery

MirrorOrch — SamplePacket lifecycle

SflowOrch

Unit (mock) tests

VS integration tests

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Janetxxx commented Apr 21, 2026 •

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prsunny commented Jun 18, 2026 •

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