Nftables

Initial Config

1. Disable firewalld and enable nftables:
   1. systemctl disable --now firewalld
   2. systemctl mask firewalld
   3. nft flush ruleset
   4. systemctl enable --now nftables
2. Create a new inet table called "filter":
   nft add table inet filter
3. Create a chain called "INPUT" (in the filter table):
   nft add chain inet filter INPUT { type filter hook input priority 0 \; policy accept\; }
   • defines type: filter, hook: input, priority: 0 (highest)
4. Create a new rule allowing localhost traffic (in the INPUT chain):
   nft add rule inet filter INPUT iif lo accept
5. Create a new rule allowing established connections (in the INPUT chain):
   nft add rule inet filter INPUT ct state established,related accept
6. Create a new rule allowing 80/tcp and 22/tcp (in the INPUT chain):
   nft add rule inet filter INPUT tcp dport {80, 22} accept
   • Obviously this is optional and dependent on what you're trying to accomplish.
7. Create a new rule to count and drop all other traffic (in the INPUT chain):
   nft add rule inet filter INPUT counter drop
   • Probably a good idea to add this last (at the bottom of the chain):
   • or, better yet... log and drop traffic:
     nft add rule inet filter INPUT log prefix \"Dropped\: \" flags all counter drop comment \"default drop all\"

Other Commands

List filter table (of type inet), with line/position (handle) numbers

nft -a list table inet filter

Add new rule at a given position

(inserts before handle 6)

nft insert rule inet filter INPUT position 6 ip saddr 10.144.91.0/24 udp dport 1812 accept

(inserts after handle 7)

nft add rule inet filter INPUT position 7 ip saddr 10.144.91.0/24 udp dport 1813 accept

Delete rule at a given position

nft delete rule inet filter INPUT handle 5

List all rules

nft list ruleset

Export all rules to a file

nft list ruleset > <file>

Import rules from a file

nft -f <file>

Save rules (make changes persistent)

nft list ruleset > /etc/sysconfig/nftables.conf

Other

Disable Console Logging

Edit the file /etc/sysctl.conf Add the following line:

kernel.printk = 4 1 1 7

The above changes will be effective at reboot or immediately using the following command:

/sbin/sysctl -p /etc/sysctl.conf

You can check the current setting with:

cat /proc/sys/kernel/printk