Why does iptables fail with 'xt_owner module missing' in a sandbox?

The xt_owner kernel module is not currently available in E2B’s sandbox kernel. As a result, iptables rules that depend on it — most commonly NAT REDIRECT with --uid-owner or --gid-owner (used in transparent proxy setups) — will fail with:

Warning: Extension owner revision 0 not supported, missing kernel module?

The command exits with code 4, which aborts any script running under set -e.

Workaround: use nftables

nftables is the modern replacement for iptables and does not depend on the xt_owner module for owner-based matching. If you’re setting up a transparent proxy or any rule that matches on user/group ownership, use nftables instead.