Firewall mark classifier in tc(8) LinuxFirewall mark classifier in tc(8)
fw - fwmark traffic control filter
tc filter ... fw [ classid CLASSID ] [ action ACTION_SPEC ]
the fw filter allows one to classify packets based on a previously set fwmark by iptables. If the masked value of the fwmark matches the filter's masked handle, the filter matches. By default, all 32 bits of the handle and the fwmark are masked. iptables allows one to mark single packets with the MARK target, or whole connections using CONNMARK. The benefit of using this filter instead of doing the heavy-lifting with tc itself is that on one hand it might be convenient to keep packet filtering and classification in one place, possibly having to match a packet just once, and on the other users familiar with iptables but not tc will have a less hard time adding QoS to their setups.
classid CLASSID Push matching packets to the class identified by CLASSID. action ACTION_SPEC Apply an action from the generic actions framework on matching packets.
Take e.g. the following tc filter statement: tc filter add ... handle 6 fw classid 1:1 will match if the packet's fwmark value is 6. This is a sample iptables statement marking packets coming in on eth0: iptables -t mangle -A PREROUTING -i eth0 -j MARK --set-mark 6 Specific bits of the packet's fwmark can be set using the skbedit action. For example, to only set one bit of the fwmark without changing any other bit: tc filter add ... action skbedit mark 0x8/0x8 The fw filter can then be used to match on this bit by masking the handle: tc filter add ... handle 0x8/0x8 fw action drop This is useful when different bits of the fwmark are assigned different meanings.
tc(8), iptables(8), iptables-extensions(8), tc-skbedit(8)
This page is part of the iproute2 (utilities for controlling TCP/IP networking and traffic) project. Information about the project can be found at ⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩. If you have a bug report for this manual page, send it to firstname.lastname@example.org, email@example.com. This page was obtained from the project's upstream Git repository ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on 2023-06-23. (At that time, the date of the most recent commit that was found in the repository was 2023-06-09.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to firstname.lastname@example.org iproute2 21 Oct 20F1i5rewall mark classifier in tc(8)
Pages that refer to this page: tc(8)