[client] Use management-provided dns forwarder port on the client side

[lixmal]

Describe your changes

• Makes routing client respect management-provided dns forwarder port to keep compatibility with older routing peers

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)

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Documentation

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• I added/updated documentation for this change
• Documentation is not needed for this change (explain why)

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Paste the PR link from https://github.com/netbirdio/docs here:

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[Copilot]

Pull Request Overview

This PR makes the DNS forwarder port configurable and dynamic based on peer versions, replacing the hardcoded ForwarderClientPort constant. The management server now computes an appropriate forwarder port based on peer capabilities and sends it to clients via the DNS configuration.

• Adds ForwarderPort field to DNS configuration structures for transmitting the port from management server to clients
• Implements dynamic port computation in the route manager using atomic operations for thread-safe updates
• Updates DNS interceptor to use the dynamic forwarder port instead of the hardcoded constant

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
dns/dns.go	Adds ForwarderPort field to the DNS Config struct
client/internal/routemanager/manager.go	Adds atomic dnsForwarderPort field and SetDNSForwarderPort method to manage the port dynamically
client/internal/routemanager/common/params.go	Adds ForwarderPort field to handler parameters for passing the atomic port reference
client/internal/routemanager/dnsinterceptor/handler.go	Updates DNS interceptor to use the dynamic forwarder port from atomic storage instead of the hardcoded constant
client/internal/engine.go	Extracts DNS config to call SetDNSForwarderPort and sets default fallback when forwarder port is 0

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
1 Accepted issue

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

See analysis details on SonarQube Cloud

[Copilot]

Pull Request Overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

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