TC-CGROUP(8)

💖 CGROUP(8) — Cgroup Classifier in tc(8) 💖

✨ NAME ✨

okay so the manual name here is cgroup 🎀 and it's a control group based traffic control filter 💅

🦋 SYNOPSIS 🦋

tc filter ... cgroup [ match EMATCH_TREE ] [ action ACTION_SPEC ]

🌸 DESCRIPTION 🌸

okay bestie, this filter is basically a hint for tc 🧚 it tells tc to use the class ID of the net_cls control group that the process a packet came from belongs to, and to classify with that 💜 it's giving targeted ✨ and obviously it only really matters for packets generated locally on the machine 🙈

🍓 OPTIONS 🍓

• action ACTION_SPEC — slap an action from the generic actions framework onto packets that match 🔥
• match EMATCH_TREE — match packets using the extended match infrastructure 💅 check out tc-ematch(8) for the full scoop on what syntax is allowed in EMATCH_TREE 🫶

🧚 EXAMPLES 🧚

ngl this part is the main event 😭 first you need a net_cls control group, and then you gotta give it a class and some process IDs. this makes a net_cls cgroup called "foobar" 🎀:

modprobe cls_cgroup
mkdir /sys/fs/cgroup/net_cls
mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls
mkdir /sys/fs/cgroup/net_cls/foobar

next up, to give the cgroup a class ID you make a file called net_cls.classid that holds the class ID as a hexadecimal, 64bit wide number 🌈 the upper 32bits are for the major handle and the rest is the minor. so a class ID like ff:be gets written as 0xff00be (leading zeroes can be left off) ✨ continuing the example, this gives foobar class ID 1:2:

echo 0x10002 > /sys/fs/cgroup/net_cls/foobar/net_cls.classid

last step, toss some PIDs into the cgroup:

echo 1234 > /sys/fs/cgroup/net_cls/foobar/tasks
echo 5678 > /sys/fs/cgroup/net_cls/foobar/tasks

and that's it!! just attach a cgroup filter to a qdisc and packets from PIDs 1234 and 5678 get pushed into class 1:2 👑 iconic, periodt 💀

🦋 SEE ALSO 🦋

tc(8), tc-ematch(8), and the file Documentation/cgroups/net_cls.txt of the Linux kernel tree 📚

iproute2 · 21 Oct 2015 · Cgroup classifier in tc(8) 🌈 that's the source, version, and date for the receipts, bestie 💜 love you, mean it 🫶✨