So the already established connection on port 22 80 or 443 is allowed to persist indefinitely (as long as adequate traffic persists) despite the new ruleset forbidding it now. This rule queries conntrack which has still a valid entry and will continue allowing traffic. Switching rules this way (or using iptables-restore) won't kill active connections because of the stateful short-circuiting rule. ![]() If there are dynamic components (dynamic IPs, temporary IP bans etc.) one should adapt the rules with some logic, for example with user-defined chains or the companion ipset tool and associated match and target.Įstablished connections will stay established with the current method This file can easily edited directly since it's the usual syntax at least for the rules themselves. Once one have a working ruleset, one should not use shell commands to load it back, but instead use iptables-save to dump the rules in a file and iptables-restore to load them back from this file. A packet will either see the first ruleset, or see the second ruleset, but never an intermediate state. By contrast, iptables-save atomically saves the ruleset, and the reverse iptables-restore atomically restores the ruleset (at least for a given table). Is this a secure way to protect from external ip? And is this the right way to block connection from ip allowed in first iptables when the second is actived?Īdding rules one by one changes the firewall one rule at a time, with a possibly unwanted intermediate state for the firewall ruleset. When I switch from the first to the second iptables, how I'm sure that all alive connection will be killed from the ip saved in "csa"? usr/sbin/iptables -A INPUT -p tcp -s MY_SECOND_IP -dport 3306 -m conntrack -ctstate NEW,ESTABLISHED -j ACCEPT usr/sbin/iptables -A INPUT -p tcp -m tcp -s $csa -dport 443 -m connlimit -connlimit-upto 1 -j ACCEPT usr/sbin/iptables -A INPUT -p tcp -m tcp -s $csa -dport 80 -m connlimit -connlimit-upto 1 -j ACCEPT usr/sbin/iptables -A INPUT -p tcp -m tcp -s $csa -dport 22 -m connlimit -connlimit-upto 1 -j ACCEPT usr/sbin/iptables -A INPUT -m state -state ESTABLISHED -j ACCEPT ![]() usr/sbin/iptables -A INPUT -i lo -j ACCEPT The second iptables replace the first at 15:00.
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