Add comprehensive OSPF routing filter rules with documentation

[gpas45]

Summary

Enhanced the OSPF filter rules configuration with improved documentation, explicit reject rules, and clearer structure. The changes make the filtering logic more maintainable and self-documenting while maintaining the same core functionality of restricting OSPF routes to RFC1918 private networks.

Key Changes

• Added comprehensive header comments explaining the purpose of the filters in both English and Russian, including the goal of preventing public prefixes and default routes from leaking into the OSPF domain
• Reorganized filter rules with clear section headers separating inbound (ospf-in) and outbound (ospf-out) filter chains
• Added explicit reject rules at the end of each chain for clarity and to document the default-deny behavior
• Added default route filtering with explicit rules to drop 0.0.0.0/0 in both directions
• Added descriptive comments to each filter rule explaining what it does
• Included configuration instructions showing how to bind the filter chains to an OSPF instance
• Added helpful tips section with guidance on:
  • Explanation of the explicit reject rule for self-documentation
  • How to restrict more specific routes by adjusting dst-len boundaries
  • Where to find the OSPF instance name

Implementation Details

• Filter logic remains functionally equivalent to the original (accepts 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 with appropriate prefix lengths)
• New explicit default route rejection prevents accidental propagation of 0.0.0.0/0
• Configuration is now more discoverable with inline instructions for applying the filters
• Comments are provided in both English and Russian to match the existing codebase style

https://claude.ai/code/session_015PYMYtCPwvUpUqkfFD5UL6