[client] Don't deactivate upstream resolvers on failure

[lixmal]

Describe your changes

• Improve upstream timeout based on the amount of upstream servers (raised from 2s default)
• Add management resolver that caches management related domains (management, signal, relay, flow, turn, stun)
  • Populated before dns server start
  • Updated on network map change
• Remove upstream resolver deactivation based on failed requests
• Add debug output if upstream timed out: which peer routes this nameserver and what's its state

Issue ticket number and link

Stack

Checklist

• Is it a bug fix
• Is a typo/documentation fix
• Is a feature enhancement
• It is a refactor
• Created tests that fail without the change (if possible)
• Extended the README / documentation, if necessary

By submitting this pull request, you confirm that you have read and agree to the terms of the Contributor License Agreement.

[Copilot]

Pull Request Overview

This PR refactors DNS handling to improve robustness, adds caching for management domains, and simplifies configuration management.

• Introduces a fixed DNS timeout and detailed debug logging for upstream timeouts, removing dynamic deactivation of resolvers.
• Extends login and engine startup flows to carry management configuration through DNS cache population.
• Refactors DNS server and upstream resolver constructors to use structured config types and adds comprehensive management-domain caching and tests.

Reviewed Changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
client/internal/routemanager/dnsinterceptor/handler.go	Use a constant DNS timeout, add context-based ExchangeWithFallback, and debugPeerTimeout logic
client/internal/login.go	Updated doMgmLogin to return login response, adjusted callers to handle new return values
client/internal/engine.go (+ engine_test.go)	Changed Engine.Start signature to accept NetbirdConfig and mgmtURL, added PopulateNetbirdConfig
client/internal/dns/upstream.go (+ upstream_*.go + tests)	Refactored upstream resolver: unified timeouts, removed deactivation logic, added client timeouts
client/internal/dns/server.go (+ server_test.go)	Switched NewDefaultServer to accept DefaultServerConfig, integrated management cache resolver
client/internal/dns/mgmt/mgmt.go (+ mgmt_test.go)	Added management-domain caching resolver with full test coverage
client/internal/dns/config/domains.go (+ domains_test.go)	Introduced ServerDomains extraction and robust URL-to-domain parsing with tests
client/internal/connect.go	Updated ConnectClient.run to pass NetbirdConfig and management URL to engine.Start

Comments suppressed due to low confidence (1)

client/internal/routemanager/dnsinterceptor/handler.go:597

• nbdns.FormatPeerStatus does not exist in the nbdns module; the FormatPeerStatus function lives in the internal dns package. Import and call the correct package (e.g., client/internal/dns) or move FormatPeerStatus into nbdns to prevent a missing-reference compilation error.

	return fmt.Sprintf(" (peer %s)", nbdns.FormatPeerStatus(&peerState))

[hurricanehrndz]

Patch is very good, it does solve the issue but introduces system DNS cache poisoning. It might not be worth it at this time.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
3 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud