fix: Adding ipv6 check on the node init function

[MitchLewis930]

PR_050

[greptile-apps]

Greptile Overview

Greptile Summary

Added early validation in WaitForNodeInformation to check if a node has an IPv6 address when EnableIPv6 is configured. Previously, Cilium pods would fail later in the initialization process on single-stack (IPv4-only) clusters when IPv6 was enabled in the configuration, making troubleshooting more difficult. The new check returns an explicit error early, preventing pods from starting when the node lacks required IPv6 support.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The change adds a targeted validation check that fails fast when IPv6 is enabled but the node lacks an IPv6 address. The logic is straightforward, follows existing patterns in the codebase (similar to wireguard agent validation), and addresses a real operational issue where Cilium pods would fail later with less clear error messages.
• No files require special attention

Important Files Changed

Filename	Overview
daemon/k8s/init.go	Added IPv6 address validation to prevent Cilium pods from failing on single-stack clusters when IPv6 is enabled

Sequence Diagram

sequenceDiagram
    participant API as Kubernetes API
    participant WNI as WaitForNodeInformation
    participant RNI as retrieveNodeInformation
    participant Node as Node Object
    participant Config as option.Config
    participant Logger as Log
    
    WNI->>Config: Check nodeName
    alt nodeName is empty
        WNI-->>WNI: Return nil (skip validation)
    else nodeName exists
        WNI->>RNI: retrieveNodeInformation(ctx, log, localNode, localCiliumNode)
        RNI->>API: Watch for Node/CiliumNode events
        API-->>RNI: Return node resource
        RNI-->>WNI: Return Node object
        
        alt Node object received
            WNI->>Node: GetNodeIP(false) - IPv4
            Node-->>WNI: nodeIP4
            WNI->>Node: GetNodeIP(true) - IPv6
            Node-->>WNI: nodeIP6
            WNI->>Logger: Log node information
            
            Note over WNI,Config: New IPv6 validation check
            WNI->>Config: Check EnableIPv6
            alt EnableIPv6 && nodeIP6 == nil
                WNI->>Logger: Error: No IPv6 support
                WNI-->>WNI: Return error (node has no IPv6)
            else IPv6 check passes
                WNI->>WNI: useNodeCIDR(n)
                WNI-->>WNI: Success
            end
        else Node object not received
            alt CIDR required
                WNI-->>WNI: Return error (unable to derive PodCIDR)
            else CIDR not required
                WNI-->>WNI: Success
            end
        end
    end

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