T7909: FRR EIGRP - Handling for malformed update msgs

[ritika0313]

This patch fixes the crashes happening upon receipt of malformed update packets carrying routes other than IPv4 Internal routes. For packets carrying IPv4 Inernal routes, a subsequent patch is required

Change summary

This patch fixes the crashes happening upon receipt of malformed update packets carrying routes other than IPv4 Internal routes. The crash happens because the code is trying to read more data in TLVs than is available in the packet stream. Fix is implemented by first checking the length of available data in the stream before reading/accessing it. If sufficient data is not present to read, it is handled appropriately.

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

Related PR(s)

Checklist:

• [x ] I have read the CONTRIBUTING document
• [x ] I have linked this PR to one or more Phabricator Task(s)
• [x ] My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[github-actions]

👍
No issues in PR Title / Commit Title

[Copilot]

Pull Request Overview

This PR adds a patch to FRR's EIGRP implementation to fix crashes caused by malformed update packets. The patch addresses the issue where code attempts to read more data from TLV (Type-Length-Value) structures than is available in the packet stream.

• Adds bounds checking before reading packet data to prevent crashes
• Implements graceful handling of unknown TLV types with proper validation
• Adds safety checks for packet header lengths and TLV structure integrity

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[github-actions]

All contributors have signed the CLA ✍️ ✅
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[ritika0313]

I have read the CLA Document and I hereby sign the CLA

[sever-sever]

Merged in the upstream FRRouting/frr#19699

[dmbaturin]

We do not expose EIGPR yet but the patch will not harm, so let's merge it.