draft: Warn user when DNS is not working

[nicoschmdt]

fix: #690

[github-actions]

Automated PR Review

0. Summary

• Verdict: MINOR SUGGESTIONS ✏️

Adds a DNS-failure warning path to the internet-status tray. Backend helper service now surfaces socket.gaierror as a dns sentinel on WebsiteStatus.error; the frontend store derives a dns_failure flag from the mix of IP-only and named probes and, when true, swaps the tray icon/tooltip and deep-links the network-interface menu to the DNS configuration tab on open.

1. Correctness & Implementation Bugs

• 1.1 [minor] core/frontend/src/store/helper.ts:108-119 — when every IP-based probe times out (ip_sites.length === 0) the first branch is skipped, and if link_up is also false the second branch is skipped too, leaving a previously-true dns_failure stuck on forever until an IP probe answers again. In today's Website enum only Cloudflare is IP-based, so a single hiccup at 1.1.1.1 freezes the DNS warning. Consider also clearing dns_failure when every decided named site is online regardless of IP probe presence — that's a strong positive signal that DNS is working.
• 1.2 [minor] core/frontend/src/components/app/NetworkInterfaceMenu.vue:61-66 — mounted() reads initialPage once. If the parent re-passes a different value while the modal is open (e.g. dns_failure flips), the tab won't move. Today v-if="show_menu" on the parent means the component is recreated on each open so this is fine in practice, but a watch on initialPage (or using it as a computed default for page_selected) is more robust and matches Vue reactivity expectations.

6. Code Quality & Style

• 6.1 [nit] core/frontend/src/components/app/InternetTrayMenu.vue:58-83 — the new dns_failure computed is defined but the tooltip and icon computed properties still reach for helper.dns_failure directly. Pick one style; using this.dns_failure throughout removes the double reference and is consistent with the rest of the file's use of computed indirection.
• 6.2 [nit] core/services/helper/main.py:461 and core/frontend/src/store/helper.ts:116 — the literal "dns" is now a cross-service protocol string (alongside "timeout"). Consider promoting both to a shared enum-ish constant on each side (WebsiteErrorSentinel.DNS = "dns") so a rename on one side is caught by the other. Minor since there are only two values today.

7. Tests

• 7.1 [minor] No pytest coverage for the new dns_error propagation in SimpleHttpResponse / check_website, and no unit coverage for the store's DNS classification logic in checkInternetAccess. The classification branches (IP-only down, mixed named results, all-named-dns, all-named-online) are the interesting ones to lock down; a small test that constructs a fake SiteStatus payload and asserts dns_failure/has_internet transitions would be cheap insurance.

8. Documentation

• 8.1 [nit] PR title still starts with draft: even though isDraft is false. Drop the prefix before merge so the squash-commit subject reads cleanly.
• 8.2 [nit] core/services/helper/main.py:460 — the comment "Sentinel, like the 'timeout' one set by check_internet_access" is helpful, but the twin sentinel is set in check_internet_access on line 499 of the same file; a # see also: check_internet_access reference (or the shared constant from 6.2) makes the coupling harder to miss.

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