Linux Packet Filtering and iptables - Explicit matches

Aug 20, 2015 · This mark does not touch the actual packet, but adds the mark to the kernel’s representation of the packet. The Raw Table. The iptables firewall is stateful, meaning that packets are evaluated in regards to their relation to previous packets. iptables -A PREROUTING -t mangle -i eth1 -m mark ! --mark 0xffff -j DROP iptables -A PREROUTING -t mangle -i eth2 -m mark ! --mark 0xffff -j DROP And the following commands to make all nodes see the same packets: The most common CONNMARK setup consist in putting connection mark on packet when they arrive and saving packet mark to connection when they leave. In term of iptables, this translates as: iptables -A PREROUTING -t mangle -j CONNMARK --restore-mark iptables -A POSTROUTING -t mangle -j CONNMARK --save-mark Code examples A simple example Marc Boucher made Rusty abandon ipnatctl by lobbying for a generic packet selection framework in iptables, then wrote the mangle table, the owner match, the mark stuff, and ran around doing cool stuff everywhere.

MARK associates "marks" with packets. CONNMARK associates "marks" with connections. The second one is useful because you can mark all the packets of a connection or related to a connection with the same mark (for example, FTP). Another usefull use of CONNMARK is that you can mark packets using the criteria that only matches with the first packet.

Netfilter Connmark – To Linux and beyond

Jan 29, 2010

linux - How to iptables REJECT outgoing traffic? - Server So I have a few docker containers running and each of them configured to use a certain network interface for outgoing traffic. Let's say for an example that there is a docker network called docker MetalLB iptables on bare metal cluster : kubernetes So now I'm trying to forward all tcp packages on port 80 to the ExternalIP of the ingress by using the POSTROUTING and PREROUTING chains in the iptables, but somehow the packgages just don't go through. I've set the PREROUTING rule to: iptables -t nat -I PREROUTING -p tcp --dport 80 -i enp0s31f6 -j DNAT --to-destination The --set-mark match takes an integer value. For example, we may set mark 2 on a specific stream of packets, or on all packets from a specific host and then do advanced routing on that host, to decrease or increase the network bandwidth, etc.