Ignore scoped link-local IPv6 DNS

[melo-crypto]

No description provided.

[j-sallyjin]

PR Review Summary

✅ What looks good

• Correctly separates IPv4 and IPv6 DNS route handling in updateRouteForDNS(), avoiding the previous early return where missing IPv4 gateway could skip IPv6 DNS routes.
• Adds getRoutableDns6Nameservers() instead of changing the general getDns6Nameservers() contract, preserving link-local DNS visibility for non-routing callers.
• Updates routing paths to use the routable IPv6 DNS helper before programming DNS-specific IPv6 routes.
• Added tests covering preservation of link-local IPv6 DNS in the general helper and route programming for IPv4 plus routable IPv6 DNS.
• Issue requirement coverage: No linked issue found.

⚠️ Issues found

No blocking correctness, security, concurrency, or networking issues found in the provided diff.

💡 Suggestions

• Add a direct unit test for getRoutableDns6Nameservers() with scoped link-local, unscoped link-local, global IPv6, and invalid input. The current route test stubs this helper, so it does not directly verify the new filtering behavior.
• Consider adding focused coverage for the routing_plugin.js call sites, since those are the other production paths changed to depend on the new helper.

Verdict

APPROVE

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Repo: firewalla/firerouter
PR: #1928
Head SHA: ccc2b3460f49b42865f666ce1adf2d77c685d671
Checked at: 2026-06-18 17:17:55 CST