Create per-device ZTP firmware symlink from sonic_parameters.version

[berendt]

Summary

Adds support for per-device SONiC firmware selection to the sync sonic command, matching the ZTP dynamic-url switch in osism/ansible-collection-services#2131.

That PR changed the ZTP firmware install to a dynamic-url built from <prefix><identifier><suffix> (identifier serial-number), so each switch fetches sonic-broadcom-enterprise-base_<serial>.bin during ZTP. For that name to resolve to the right image, a per-serial link to the version-specific image must exist. The serial→version mapping lives in NetBox (sonic_parameters.version), and sync sonic already writes the per-serial artefacts into the export directory.

Changes

• Settings (settings.py): new SONIC_FIRMWARE_DIR / _PREFIX / _SUFFIX / _IDENTIFIER, mirroring the ansible httpd role defaults. SONIC_FIRMWARE_DIR defaults to the same httpd-served directory as the config exports (/etc/sonic/export).
• export_firmware_link() (exporter.py): creates <prefix><serial><suffix> as a relative symlink to <prefix><version><suffix>. Reconciled on every run (missing/stale/wrongly-pointed links are repaired), skips devices without a configured version, and raises on real failures so they surface as a non-zero task rc. The target image is provided out of band (e.g. downloaded by metalbox), so a dangling link until it arrives is expected.
• sync_sonic (sync.py): reads sonic_parameters.version per device (like hwsku / config_version) and passes it to the exporter. config_db.json and the CONFIG DB VERSION are untouched.

For the example device (serial 732656X2419308, version: 4.4.2) this produces:

/etc/sonic/export/sonic-broadcom-enterprise-base_732656X2419308.bin
    -> sonic-broadcom-enterprise-base_4.4.2.bin

Tests

• 13 tests in test_exporter.py (identifier/target naming, serial fallback, reconciliation, self-reference guard, error paths).
• 3 tests in test_sync.py (version → firmware link, None when absent, rc=1 on failure); patch_sync_deps and make_device extended accordingly.

🤖 Generated with Claude Code

[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• The extraction of sonic_parameters.version in sync_sonic is quite verbose and duplicates the nested custom_fields access logic used for config_version; consider using a small helper (or .get chains) to centralise and simplify reading sonic_parameters fields.
• In export_firmware_link, any SONIC_FIRMWARE_IDENTIFIER value other than serial-number silently falls back to hostname; it may be worth explicitly validating the setting (e.g. warning on unrecognised values) to make misconfiguration easier to spot.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The extraction of `sonic_parameters.version` in `sync_sonic` is quite verbose and duplicates the nested `custom_fields` access logic used for `config_version`; consider using a small helper (or `.get` chains) to centralise and simplify reading `sonic_parameters` fields.
- In `export_firmware_link`, any `SONIC_FIRMWARE_IDENTIFIER` value other than `serial-number` silently falls back to hostname; it may be worth explicitly validating the setting (e.g. warning on unrecognised values) to make misconfiguration easier to spot.

## Individual Comments

### Comment 1
<location path="osism/settings.py" line_range="80-83" />
<code_context>
+# sonic_parameters.version custom field. The defaults mirror the ansible
+# httpd role and place the links in the same httpd-served directory as the
+# config exports (SONIC_EXPORT_DIR).
+SONIC_FIRMWARE_DIR = os.getenv("SONIC_FIRMWARE_DIR", "/etc/sonic/export")
+SONIC_FIRMWARE_PREFIX = os.getenv(
+    "SONIC_FIRMWARE_PREFIX", "sonic-broadcom-enterprise-base_"
</code_context>
<issue_to_address>
**suggestion:** Avoid duplicating the export directory default by reusing the existing SONIC_EXPORT_DIR setting.

This adds a second path defaulting to `/etc/sonic/export`, while `SONIC_EXPORT_DIR` already represents the canonical export directory. To avoid config drift if only one env var is overridden, derive the firmware directory from the existing setting when the firmware-specific env var is unset:

```python
SONIC_FIRMWARE_DIR = os.getenv("SONIC_FIRMWARE_DIR", SONIC_EXPORT_DIR)
```

This keeps a single source of truth for the base export path unless a separate firmware directory is explicitly configured.

```suggestion
# sonic_parameters.version custom field. The defaults mirror the ansible
# httpd role and place the links in the same httpd-served directory as the
# config exports (SONIC_EXPORT_DIR).
SONIC_FIRMWARE_DIR = os.getenv("SONIC_FIRMWARE_DIR", SONIC_EXPORT_DIR)
```
</issue_to_address>

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}