[action] [PR:4638] [techsupport] Skip switch-only collectors on Switch-BMC

[mssonicbld]

What I did

generate_dump (the engine behind show techsupport) ran the full switch data-plane collection unconditionally. On a SONiC Switch-BMC — a control-plane-only platform with no ASIC/SDK, no front-panel ports, no FRR/vtysh, no swss/bgp/syncd containers, no STP, and an ARM/aspeed SoC that lacks some sysfs paths and tools — this produced a large number of spurious errors and irrelevant/empty sections in the techsupport bundle.

This change makes generate_dump Switch-BMC aware so show techsupport completes cleanly on a Switch-BMC, while behavior on regular switches is unchanged.

Part of the SONiC Switch-BMC enablement.

How I did it

• Add an IS_SWITCH_BMC flag, set from switch_bmc=1 in platform_env.conf (mirroring the existing IS_SUPERVISOR handling).
• Gate switch-only collectors on it so they self-skip on a Switch-BMC: FRR/BGP/EVPN/BFD, ASIC/SDK health events, front-panel interface/transceiver, gearbox, STP, swss/bgp docker logs, hdparm, the SAI dump, and the port-counter snapshots.
• Keep platform-agnostic collectors: the generic show ip interface L3 summary (incl. management), LLDP, NAT/conntrack, and platform info.
• Harden generic fallbacks so absent/empty paths no longer error:
  • record_missing_path replaces the broken echo > $TARDIR/$f fallback in save_proc/save_sys;
  • save_pstore handles absent/empty/populated without a failing glob;
  • sed_if_exists guards optional secret-scrub files.

How to verify it

On an AST2700-based SONiC Switch-BMC (switch_bmc=1):

1. show techsupport → completes with exit 0, no spurious data-plane errors, and a valid gzip tarball under /var/dump.
2. Confirm the switch-only sections are skipped (no FRR/BGP/STP/transceiver errors) while the platform/LLDP/NAT/management-interface sections are present.

On a regular (non-Switch-BMC) switch the behavior is unchanged: IS_SWITCH_BMC=false, so every collector runs exactly as before, and the empty-port-config path stays fatal.

Validated on a live AST2700 SONiC Switch-BMC: multiple full show techsupport runs (default, --silent, --debug-dump), all exit 0 and gzip-valid; the non-BMC fatal paths confirmed unchanged.

Previous command output (if the output of a command-line utility has changed)

On a Switch-BMC, show techsupport previously emitted many collector failures to the console/log (e.g. FRR/vtysh, STP/stpctl, front-panel interface transceiver, swss/bgp docker-log lookups) and wrote empty/error sections into the bundle.

New command output (if the output of a command-line utility has changed)

On a Switch-BMC, show techsupport now completes with exit 0 and no spurious errors; the inapplicable switch-only sections are omitted, and the platform/LLDP/NAT/management sections are retained.

Signed-off-by: Sonic Build Admin sonicbld@microsoft.com

[mssonicbld]

Original PR: sonic-net/sonic-utilities#4638

[mssonicbld]

/azp run

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