bugfix(controller): configure MTU (#3114)

[bgm-malbeclabs]

Summary of Changes

MTU 2048 was hardcoded but now for WAN / DZX interfaces it's 2048 and for CYOA/DIA it's set to 1500.

Closes #3114

Testing Verification

• Tests have been updated with a different MTU

[Copilot]

Pull request overview

This PR makes the controller-rendered interface MTU configurable by sourcing MTU from the interface model rather than hardcoding 2048, and updates related fixtures/tests accordingly.

Changes:

• Render per-interface MTU in the device config template (instead of hardcoded 2048).
• Extend the controller Interface model to carry MTU from on-chain/serviceability data (and propagate it to generated parent interfaces).
• Update unit test inputs and expected fixture outputs to use a non-default MTU (e.g., 9100), plus a changelog entry.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
controlplane/controller/internal/controller/templates/tunnel.tmpl	Switches interface MTU rendering from hardcoded value to model-driven MTU.
controlplane/controller/internal/controller/server_test.go	Updates test interface objects to include MTU.
controlplane/controller/internal/controller/render_test.go	Updates render tests to include MTU on interfaces.
controlplane/controller/internal/controller/models.go	Adds Mtu to controller Interface and maps it from serviceability interfaces / into parent derivation.
controlplane/controller/internal/controller/fixtures/interfaces.txt	Updates expected rendered interface MTU values.
controlplane/controller/internal/controller/fixtures/e2e.tmpl	Updates expected rendered interface MTU values in e2e fixture template.
controlplane/controller/internal/controller/fixtures/base.config.txt	Updates expected base config MTU values.
controlplane/controller/internal/controller/fixtures/base.config.drained.txt	Updates expected drained base config MTU values.
CHANGELOG.md	Notes that MTU is now configurable.

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[ben-malbeclabs]

@bgm-malbeclabs please ensure that the MTU on CYOA and/or DIA interfaces are defaulting to 1500 bytes unless specified.

[bgm-malbeclabs]

@bgm-malbeclabs please ensure that the MTU on CYOA and/or DIA interfaces are defaulting to 1500 bytes unless specified.

It defaults to 1500:

    /// MTU
    #[arg(long, default_value = "1500")]
    pub mtu: u16,

[Copilot]

Pull request overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 1 comment.

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[ben-malbeclabs]

LGTM