TC-ROUTE(8)

✨ Route classifier in tc(8) ✨

okay bestie, let's talk about the route filter! 🎀 It's a traffic control filter for tc(8), and it's the one that sorts packets by their routing table entries 🦋

💖 NAME

route - route traffic control filter

🧚 SYNOPSIS

tc filter ... route [ from REALM | fromif TAG ] [ to REALM ] [ classid
        CLASSID ] [ action ACTION_SPEC ]

🌸 DESCRIPTION

Match packets based on routing table entries. ✨ The whole vibe of this filter is that you can give a routing table entry a realm 👑 For any packet this filter looks at, it does a routing table lookup, grabs the returned realm, and uses that to decide whether the packet is a match or not 💅

💜 OPTIONS

• action ACTION_SPEC — slap an action from the generic actions framework onto every matching packet ✨
• classid CLASSID — yeet matching packets straight into the class identified by CLASSID 🚀
• from REALM
• fromif TAG — do source route lookups 🔍 TAG is the name of an interface, and it has to actually exist on the system when you run tc or it's a no-go 🙈
• to REALM — match if the normal (aka destination) routing hands back the given REALM 🦋

🎀 EXAMPLES

Okay so imagine the subnet 192.168.2.0/24 is attached to eth0 🌈

ip route add 192.168.2.0/24 dev eth0 realm 2

Next up, this route filter will catch packets from that subnet 🫶

tc filter add ... route from 2 classid 1:2

and then it passes them along to class 1:2. Iconic. 💅✨

⭐ NOTES

⚠️ Heads up! Due to implementation details, realm values have to be in a range from 0 to 255, inclusive. No going outside that range 😭 Alternatively, you can use a verbose name defined in /etc/iproute2/rt_realms instead, which is lowkey so much easier to read 🍓

🌈 SEE ALSO

tc(8), ip-route(8) 💜

Thanks for hanging with me through this one, bestie! 🫶 iproute2 · 21 Oct 2015 · Route classifier in tc(8) 💖