Enhancement: Upgrade to libyang3

[bradh352]

Is it platform specific

generic

Importance or Severity

High

Description of the enhancement

SONiC currently uses 3 versions of libyang: 1.0.73, 1.0.184, and 2.1.148. All are end of life and potentially have security issues. The current release is 3.12.2 and that is what we are targeting here.

There are also numerous libyang related bugs that have been "worked around" in SONiC due to the shortcomings of libyang1. Hopefully upgrading to a modern version will resolve such issues.

Current Behavior

3 libyang versions

Proposed Behavior

single libyang version

PR Tracking Table

Legend: strikethrough = merged/done.

Foundation (merged)

PR	description
#21679	Remove libyang 1.0.184; build libyang 3.12.2 + libyang-python 3.1.0; migrate FRR to libyang3; pre-stage sonic-yang-models test cases
#21719	Port sonic-yang-models test cases
#24414	sonic-yang-mgmt: helpers to keep dependents from calling into libyang directly
#26584	Port sonic-yang-mgmt from libyang1 to libyang3 Python bindings
sonic-net/sonic-utilities#4118	sonic-utilities: remove direct dependency on libyang
sonic-net/sonic-platform-daemons#589, sonic-net/sonic-platform-common#544	Interim: install both libyang1 and libyang3
sonic-net/sonic-swss-common#973	sonic-swss-common: port to libyang3

Code port (open)

PR	description
sonic-net/sonic-mgmt-common#157	sonic-mgmt-common (Go/CVL): port to libyang3
sonic-net/sonic-mgmt#24821	sonic-mgmt: port tests/telemetry/validate_yang_events.py from libyang1 to libyang3 Python bindings (last import yang consumer in the test repo)

Buildimage — consolidated final change (open)

PR	description
#27629	Migrate the remaining buildimage consumers to libyang3, remove the libyang3-dev-done coexistence shim and the post-FRR libyang3-dev UNINSTALLS, and delete libyang1 (rules/libyang.{mk,dep}, src/libyang). Supersedes and replaces former steps 4–7 (#21718, #21752, #21789, #21790, now closed). This is the last buildimage PR to complete the migration.

Per-repo CI/build: install libyang3 debs instead of libyang1 (open)

PR	description
sonic-net/sonic-swss#4624	build-env / dev Dockerfile / README → versionless libyang3 globs
sonic-net/sonic-dbsyncd#82	azure-pipelines → libyang3_*.deb
sonic-net/sonic-restapi#189	Dockerfile / copy.sh / dependencies.conf → libyang3
sonic-net/sonic-snmpagent#377	azure-pipelines → libyang3_*.deb
sonic-net/sonic-dhcpmon#78	azure-pipelines download filter → libyang3
sonic-net/sonic-dhcp-relay#113	azure-pipelines + codeql → libyang3
sonic-net/sonic-linkmgrd#341	azure-pipelines download filters → libyang3
sonic-net/sonic-bmp#37	azure-pipelines install → libyang3_*.deb
sonic-net/sonic-gnmi#693	install-dependencies → libyang3
sonic-net/sonic-host-services#386	azure-pipelines install → libyang3_*.deb
sonic-net/sonic-mgmt-framework#161	azure-pipelines download/install → libyang3
sonic-net/sonic-platform-common#683	azure-pipelines: drop libyang1, keep libyang3
sonic-net/sonic-platform-daemons#827	azure-pipelines: drop libyang1, keep libyang3
sonic-net/sonic-stp#90	azure-pipelines install → libyang3_*.deb
sonic-net/sonic-utilities#4578	azure-pipelines / README → libyang3 (drop libyang-cpp, python3-yang→python3-libyang)
sonic-net/sonic-wpa-supplicant#115	azure-pipelines download filters → libyang3
sonic-net/sonic-platform-vpp#243	rules: migrate libyang1 make-vars (LIBYANG/LIBYANG_CPP/LIBYANG_PY3/LIBYANG2) to libyang3

Per-repo CI already migrated upstream (done)

PR	description
sonic-net/sonic-sairedis#1916	sonic-sairedis: download/install libyang3
sonic-net/sonic-dash-ha#173	sonic-dash-ha: CI deps → libyang3

Order: merge the code ports (sonic-mgmt-common#157) and the per-repo CI PRs first, then #27629 last (it removes libyang1, so it must land only after every consumer is on libyang3).