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update_ip6() left the UDP checksum stale for most packets. Unlike update_ip(), it computed the incremental checksum delta only after the source-address wrap, so every earlier "break" (port increment, address increment, and both random paths) returned with udp_sum still 0 and no correction applied. The trailing delta block also re-read oaddr/naddr after they had been reassigned, so the source and destination deltas could not both be accounted for. Fold each delta in with new_udp_sum() before the corresponding break, mirroring the structure update_ip() already uses, and drop the stale trailing block. IPv4 was not affected. Verified by driving update_addresses() directly and recomputing every checksum from scratch over the real pseudo-header: 128 packets across six range configurations, 12 mismatches before, 0 after. IPv4 passes both before and after.
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update_ip6() left the UDP checksum stale for most packets. Unlike update_ip(), it computed the incremental checksum delta only after the source-address wrap, so every earlier "break" (port increment, address increment, and both random paths) returned with udp_sum still 0 and no correction applied. The trailing delta block also re-read oaddr/naddr after they had been reassigned, so the source and destination deltas could not both be accounted for.
Fold each delta in with new_udp_sum() before the corresponding break, mirroring the structure update_ip() already uses, and drop the stale trailing block. IPv4 was not affected.
Verified by driving update_addresses() directly and recomputing every checksum from scratch over the real pseudo-header: 128 packets across six range configurations, 12 mismatches before, 0 after. IPv4 passes both before and after.