[dhcpmon] Identify parent and aggregate counter disparities by Xichen96 · Pull Request #100 · sonic-net/sonic-dhcpmon

Xichen96 · 2026-07-26T06:42:14Z

Description of PR

Report the exact parent interface and aggregate counter whose values diverged.

Dependency:

Nested PortChannel member PR [dhcpmon] Track physical members beneath VLAN PortChannels #99.

Review the final commit only:

831de60 [dhcpmon]: Track parent and aggregate counters per interface

Work item tracking

Microsoft ADO (number only): 38615656

Type of change

Approach

What is the motivation for this PR?

The existing aggregate counter alert says only that a VLAN/PortChannel
aggregate does not match. In the F2 path, operators must distinguish:

physical member -> PortChannel -> VLAN SVI

without interpreting a pre-VLAN loss as a relay drop.

How did you do it?

Evaluate activity on both the parent interface and its member-interface
aggregate, so a child-only increment is not treated as an idle window.
Populate one health state per discovered VLAN or PortChannel check, so each
parent/aggregate pair has an independent persistence counter.
Initialize those states explicitly after topology and counter discovery.
Use four aggregate checks (IPv4/IPv6 RX/TX); derive the expected ratio from
the interface topology instead of encoding equal/multiple in the check type.
Store an error format in each health state.
Keep only the event callback in health state; the threshold loop logs the
format directly with the interface name and duration. The internal
Agg-* counter name is not exposed in the user-facing message.
Remove the category-wide aggregate wrappers and global last-mismatch state.

How did you verify/test it?

On F2 hardware with PortChannel1005 down due to min_links, packets reached
the PortChannel but not Vlan1000. The equivalent comparison identified:

Parent interface: Vlan1000, member aggregate: Agg-Vlan1000-Vlan1000

No relay-disparity event was emitted for that pre-VLAN loss.

Fresh exact-head Azure PR CI is pending. No local compilation is used.

Any platform specific information?

No.

Back port request

None. This targets master only.

Tested branch

master, plus supplemental F2 topology validation with master-target PR
artifacts on SONiC 202503.

Test result

The equivalent parent/aggregate comparison identified the expected counters on
F2 hardware, and the traditional master DHCPv4/DHCPv6 regression passed
unchanged. Exact-head acceptance awaits the fresh PR build.

Documentation

Not applicable.

mssonicbld · 2026-07-26T06:42:21Z

/azp run

azure-pipelines · 2026-07-26T06:42:22Z

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azure-pipelines · 2026-07-26T06:42:30Z

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Copilot

Pull request overview

This PR enhances dhcpmon’s hierarchy mismatch alerting by recording and reporting the specific parent → immediate-child aggregate edge where DHCP counter deltas diverge, improving operator diagnostics in nested interface hierarchies (e.g., Ethernet -> PortChannel -> VLAN SVI).

Changes:

Switch aggregate-counter attribution to “immediate parent” via new dhcp_devman_get_parent_ifname() / dhcp_devman_get_agg_counter_ifname().
Capture and expose detailed mismatch context (IP family, direction, parent/child deltas, expected ratio, message type) and append it to existing hierarchy syslog alerts.
Treat “child-only activity” as non-idle for hierarchy checks to avoid masking mismatches during the evaluation window.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/util.h	Removes the old inline aggregate-counter helper in favor of devman-owned logic.
src/packet_handler.cpp	Updates cache counter aggregation to use devman immediate-parent aggregate naming.
src/health_check.cpp	Appends last recorded hierarchy-mismatch detail to existing alert syslogs.
src/dhcp_mon.cpp	Updates aggregate-counter recalculation to use devman immediate-parent aggregation.
src/dhcp_devman.h	Adds APIs to retrieve immediate parent and corresponding aggregate-counter name.
src/dhcp_devman.cpp	Implements parent/aggregate lookup and adjusts PortChannel-member mapping for nested hierarchies.
src/dhcp_device.h	Exposes accessor for the most recent hierarchy mismatch detail string.
src/dhcp_device.cpp	Records mismatch detail on first delta divergence; updates hierarchy health evaluation logic.

Comments suppressed due to low confidence (1)

src/dhcp_device.cpp:241

check_aggregate_health() takes ratio as uint8_t, but callers pass readonly_access(...).size() sums (size_t). If the parent has >255 children (e.g., large VLAN membership), the value truncates and can produce incorrect health results and misleading expected_ratio in mismatch logs. Use a wider type (e.g., size_t) for ratio here (and in check_counters_delta_expected).

static dhcp_mon_status_t check_aggregate_health(const std::string &ifname, int sock, uint8_t ratio,
                                                const int *monitored_msgs, size_t monitored_msg_cnt)
{

mssonicbld · 2026-07-26T07:28:22Z

/azp run

azure-pipelines · 2026-07-26T07:28:31Z

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Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

mssonicbld · 2026-07-26T07:53:13Z

/azp run

azure-pipelines · 2026-07-26T07:53:22Z

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Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

mssonicbld · 2026-07-26T08:07:41Z

/azp run

azure-pipelines · 2026-07-26T08:07:50Z

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Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

mssonicbld · 2026-07-27T03:33:52Z

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Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

mssonicbld · 2026-07-27T03:58:18Z

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mssonicbld · 2026-07-28T05:25:11Z

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Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

mssonicbld · 2026-07-28T05:40:57Z

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azure-pipelines · 2026-07-28T05:41:06Z

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Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

mssonicbld · 2026-07-28T05:58:51Z

/azp run

azure-pipelines · 2026-07-28T05:59:00Z

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Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

mssonicbld · 2026-07-31T17:58:05Z

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azure-pipelines · 2026-07-31T17:58:14Z

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Bound each raw-socket callback to 64 packets and reset the recvfrom address length for every receive attempt. Rename three file-scope helpers that begin with underscores because C++ reserves those identifiers in the global namespace; static linkage already marks them as internal. Replace four nullptr comparisons with NULL to match the daemon's established style. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 39f979be-d826-4d5c-949a-f20abb58bb83 Signed-off-by: Xichen96 <lukelin0907@gmail.com>

Preserve VLAN and PortChannel membership so a physical member resolves through its immediate PortChannel parent to the monitored VLAN context. Keep direct VLAN-member precedence, bound hierarchy traversal, ignore self-references, and centralize parent, context, and aggregate-name lookup. Aggregate only to the immediate parent so pre-VLAN observations are not rolled into the root VLAN counter and misreported as relay loss. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 39f979be-d826-4d5c-949a-f20abb58bb83 Signed-off-by: Xichen96 <lukelin0907@gmail.com>

Populate one state per discovered VLAN or PortChannel check, derive aggregate ratios from topology, and format aggregate disparity errors with the interface and duration. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 39f979be-d826-4d5c-949a-f20abb58bb83 Signed-off-by: Xichen96 <lukelin0907@gmail.com>

mssonicbld · 2026-07-31T19:20:40Z

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azure-pipelines · 2026-07-31T19:20:52Z

Azure Pipelines: Successfully started running 1 pipeline(s).

Copilot

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/health_check.cpp:110

Aggregate-disparity threshold logs only include the parent interface name (via state.ifname), but the PR goal is to report both the parent interface and the specific member-aggregate counter that diverged. Right now operators still can’t see which aggregate counter (e.g., Agg--) was compared.

                if (++state.count > dhcp_unhealthy_max_count) {
                    int duration = state.count * window_interval_sec;
                
                    if (state.alert) {
                        state.alert(duration);
                    }
                    syslog(LOG_ALERT, state.error_format, state.ifname.c_str(), duration);
                }

Copilot AI review requested due to automatic review settings July 26, 2026 06:42

Copilot started reviewing on behalf of Xichen96 July 26, 2026 06:42 View session

Xichen96 mentioned this pull request Jul 26, 2026

[dhcpmon] Track PortChannels under downstream VLANs #89

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Xichen96 changed the title ~~[dhcpmon] Identify hierarchy mismatch edge~~ [dhcpmon] Identify where packets stop in the interface hierarchy Jul 27, 2026

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Xichen96 force-pushed the dev/xichenlin/log-hierarchy-mismatch-edge branch from 89400cf to 257b6b3 Compare July 28, 2026 05:25

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Xichen96 force-pushed the dev/xichenlin/log-hierarchy-mismatch-edge branch from 257b6b3 to 8c0b84e Compare July 28, 2026 05:40

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Xichen96 force-pushed the dev/xichenlin/log-hierarchy-mismatch-edge branch from 8c0b84e to 3ab0905 Compare July 28, 2026 05:58

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[dhcpmon] Validate downstream DHCPv4 reply fan-out #107

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Xichen96 force-pushed the dev/xichenlin/log-hierarchy-mismatch-edge branch from 3ab0905 to 6cf80d6 Compare July 31, 2026 17:57

Xichen96 mentioned this pull request Jul 31, 2026

[dhcpmon] Validate DHCPv6 relay transformations #101

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Xichen96 force-pushed the dev/xichenlin/log-hierarchy-mismatch-edge branch from 6cf80d6 to 831de60 Compare July 31, 2026 19:20

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Description of PR

Work item tracking

Type of change

Approach

What is the motivation for this PR?

How did you do it?

How did you verify/test it?

Any platform specific information?

Back port request

Tested branch

Test result

Documentation

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mssonicbld commented Jul 26, 2026

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Xichen96 commented Jul 26, 2026 •

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