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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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6714cf5465
Explicit helper attachment via the CT target is broken with NAT if non-standard ports are used. This problem was hidden behind the automatic helper assignment routine. Thus, it becomes more noticeable now that we can disable the automatic helper assignment with Eric Leblond's: 9e8ac5a netfilter: nf_ct_helper: allow to disable automatic helper assignment Basically, nf_conntrack_alter_reply asks for looking up the helper up if NAT is enabled. Unfortunately, we don't have the conntrack template at that point anymore. Since we don't want to rely on the automatic helper assignment, we can skip the second look-up and stick to the helper that was attached by iptables. With the CT target, the user is in full control of helper attachment, thus, the policy is to trust what the user explicitly configures via iptables (no automatic magic anymore). Interestingly, this bug was hidden by the automatic helper look-up code. But it can be easily trigger if you attach the helper in a non-standard port, eg. iptables -I PREROUTING -t raw -p tcp --dport 8888 \ -j CT --helper ftp And you disabled the automatic helper assignment. I added the IPS_HELPER_BIT that allows us to differenciate between a helper that has been explicitly attached and those that have been automatically assigned. I didn't come up with a better solution (having backward compatibility in mind). Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> |
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