fix: make DNS changes reversible with a snapshot-based Undo#825
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DNS preset changes were only reversible via 'Reset to DHCP', which silently discarded any manually-configured static DNS the user had before. Applying a preset now snapshots the servers in effect first, and a new 'Undo' button on the DNS & Hosts tab restores that exact prior configuration (re-applying the previous static servers, or resetting to DHCP if that was the prior state). - DnsService.CaptureCurrentServersAsync reads and validates the current IPv4 servers; RestoreServersAsync re-applies them (empty snapshot => DHCP reset), validating every address before interpolating it into the Set script. - DnsHostsViewModel snapshots before SetDnsAsync, exposes RestorePreviousDns (admin-gated, Confirm-gated) and CanRestorePreviousDns for the button. - DnsHostsView: Undo button (SecondaryButton, AutomationProperties.Name), visible only after a change, disabled while applying. - Tests cover capture (parse/filter/DHCP-empty) and restore (re-apply/DHCP/ null-throw/invalid-address-throw) via the IPowerShellRunner seam. Closes the reversibility half of audit test finding #3 (the Confirm gate was already added in 1.20.0). README + CHANGELOG updated.
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| foreach (var server in servers) | ||
| { | ||
| if (!IPAddress.TryParse(server, out _)) | ||
| throw new ArgumentException($"Invalid DNS address in snapshot: '{server}'", nameof(servers)); | ||
| } |
| await RefreshDnsAsync(); | ||
| Log.Information("DNS restored to previous setting ({Label})", label); | ||
| } | ||
| catch (OperationCanceledException) { } |
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| catch (Exception ex) | ||
| { | ||
| Application.Current?.Dispatcher?.Invoke(() => | ||
| StatusMessage = $"Failed to restore DNS: {ex.Message}"); | ||
| Log.Error(ex, "Failed to restore previous DNS"); | ||
| } |
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What
Audit Round 4 / PR4 — closes the reversibility half of test finding #3. (The Confirm gate it also called for was already added in 1.20.0.)
DNS preset changes were only reversible via Reset to DHCP, which silently discarded any manually-configured static DNS the user had before. Now:
Changes
DnsService.CaptureCurrentServersAsync— reads + validates current IPv4 servers (filters blank/non-IP noise; empty => the adapter was on DHCP).DnsService.RestoreServersAsync— re-applies a snapshot (empty => DHCP reset), validating every address before interpolating it into theSet-DnsClientServerAddressscript.DnsHostsViewModel— snapshots beforeSetDnsAsync;RestorePreviousDnscommand is admin-gated andConfirm-gated;CanRestorePreviousDnsdrives the button.DnsHostsView— Undo button (SecondaryButton,AutomationProperties.Name, BoolToVis visibility), shown only after a change, disabled while applying.Reversibility (CODE QUALITY merge-blocker)
This makes the DNS mutation genuinely snapshot-reversible, satisfying the "every system modification must be reversible" contract.
Tests
DnsServiceTestscover capture (parse / non-IP filtering / DHCP-empty) and restore (re-apply exact servers / empty=>DHCP / null-throw / invalid-address-throw) — all via theIPowerShellRunnerseam, no live DNS touched. All literals synthetic/public (8.8.8.8,9.9.9.9).Verification
MainWindowViewModelbuilds the VM via the unchanged ctor; new service methods are additive.fix:— version bumped to 1.20.5, CHANGELOG + README updated in this PR.