Make Lucius Robust to handle invalid packets like ICMPv6 over IPV4#697
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sonikajindal
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Jun 11, 2026
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A robustness check is added to ICMP6.Rebuild() in the Lucius forwarding dataplane to handle invalid packets like ICMPv6 over IPV4.
The ICMPv6 checksum gets calculated from "IPv6 pseudo-header" which explicitly requires 16-byte IPv6 Source and Destination addresses. In this case the provided addresses were only 4 bytes long.
Added a strict validation step to ensure both IP addresses are exactly 16 bytes (protocol.SizeIP6). If they are not (as is the case with an invalid ICMPv6-over-IPv4 packet), the Rebuild() function aborts early and safely skips the checksum rewrite. This prevents the bogus checksum calculation and guarantees that opaque test payloads remain completely unmodified.