Apr 11, 2020
A mark is a special field, only maintained within the kernel, that is associated with the packets as they travel through the computer. Marks may be used by different kernel routines for such tasks as traffic shaping and filtering. As of today, there is only one way of setting a mark in Linux, namely the MARK target in iptables. This is done with the --set-mark facility. As an example, this command marks all packets destined for port 25, outgoing mail: # iptables -A PREROUTING -i eth0 -t mangle -p tcp --dport 25 \ -j MARK --set-mark 1 Aug 29, 2017 · iptables-A INPUT -p tcp -m multiport --dports 22,5901 -s 59.45.175.0/24 -j DROP. Let us consider another example. Say, you want to block ICMP address mask requests (type 17). First, you should match ICMP traffic, and then you should match the traffic type by using icmp-type in the icmp module: iptables-A INPUT -p icmp -m icmp --icmp-type 17 -j DROP 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
A mark is a special field, only maintained within the kernel, that is associated with the packets as they travel through the computer. Marks may be used by different kernel routines for such tasks as traffic shaping and filtering. As of today, there is only one way of setting a mark in Linux, namely the MARK target in iptables.
Valid targets in these modules include LOG, MARK, and REJECT, among others. Refer to the iptables man page for more information about these and other targets. This option can also be used to direct a packet matching a particular rule to a user-defined chain outside of the current chain so that other rules can be applied to the packet. iptables is the userspace command line program used to configure the Linux 2.4.x and later packet filtering ruleset. It is targeted towards system administrators. Since Network Address Translation is also configured from the packet filter ruleset, iptables is used for this, too.
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.
DD-WRT Forum :: View topic - iptables dscp mark Sep 12, 2019 iptables - remove packet mark on certain packets - Stack iptables -t mangle -A PREROUTING -p tcp --dport 443 -j MARK --set-mark 2 I am redirecting it to my proxy server later on, which is working. For one host, however, I need to remove the iptables mark (i.e. the packets will not be redirected.) I tried the following: iptables -t mangle -A PREROUTING -p tcp -s 192.168.0.47 --dport 443 -j ACCEPT Iptables Tutorial for Beginners - Key Concepts May 18, 2016