1. Make sure to disable automatic helper assignment using the command
'sudo sysctl -w net.netfilter.nf_conntrack_helper=0'
2. Use NAT
3. Set up a fault tolerant firewall system and then make the active
firewall machine to fail. The backup firewall machine will recover the
connection but lose the helper. (Simpler way is to use conntrack -I to
inject the conntrack).
On 1/31/22 20:47, Pham Thanh Tuyen wrote:
1. Make sure to disable automatic helper assignment using the command
'sudo sysctl net.netfilter.nf_conntrack_helper=0'
2. Use NAT
3. Set up a fault tolerant firewall system and then make the active
firewall machine to fail. The backup firewall machine will recover the
connection but lose the helper. (Simpler way is to use conntrack -I to
inject the conntrack).
On 1/31/22 18:20, Florian Westphal wrote:
Pham Thanh Tuyen <phamtyn@xxxxxxxxx> wrote:
[ moving to netfilter-devel ]
My name is Pham Thanh Tuyen. I found a bug related to the ctnetlink
and conntrack subsystems. Details are as follows:
1. Summary: Injected conntrack lost helper
2. Description: When a conntrack whose helper is injected from
userspace, the ctnetlink creates helper for it but NAT then loses
the helper in case the user defined helper explicitly with CT
target.
Hmm. If you insert a conntrack entry from userspace, it will already
be confirmed, so nat rules will have no effect, and template CT rules
are irrelevant wrt. to the helper, as extension can only be created if
the conntrack is not in the hash yet.
Can you describe the steps to reproduce this bug?
