## Summary
- validate handshake metadata field lengths before fixed-size reads
- reject truncated multicast advertisements before slicing the hash
payload
- add regression tests for malformed and truncated input
## Why
Both parsers currently trust length information from the incoming
payload a bit too much. Malformed network input can reach fixed-size
reads/slices and panic the process instead of being rejected cleanly.
## Testing
- go test ./...
