iptables & co.

Created on Dec 4, ’22 ・ Updated on Mar 5, ’23

Redirect port to another one

# redirect traffic going to port 80 to port 8080 on interface eth0
sudo iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 8080

iptables

# save current rules to file
sudo iptables-save | sudo tee /etc/sysconfig/iptables

# overwrite current rules with the ones in the file
sudo iptables-restore < /etc/sysconfig/iptables

# add new rules but keep current ones
sudo iptables-restore -n < /etc/sysconfig/iptable

SELinux

sudo yum install -y policycoreutils

# autorize listening on port 8080
semanage port -a -t http_port_t -p tcp 8080

# same result
semanage port -m -t http_port_t -p tcp 8080

# list all port definitions
semanage port -l

Misc

# hide private IP addresses
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

# show if port is being listened
sudo ss -tlpn | grep httpd

# see traffic from port 80 and interface eth0
tcpdump -i eth0 -n port 80