SKBPRIO(8)

💖 NAME 💖

okay bestie, meet skbprio, the SKB Priority Queue! It's a manual page from the Linux docs (SKBPRIO(8)) and it is lowkey iconic ✨

🧚 SYNOPSIS 🧚

tc qdisc ... add skbprio [ limit packets ]

🌸 DESCRIPTION 🌸

okay so SKB Priority Queue is a queueing discipline built to protect the most important packets during a denial-of-service (DoS) attack 🛡️🔥. Every packet has a priority stored in skb->priority, and a higher value puts the packet closer to the exit of the queue 🦋. When the queue is full, the lowest priority packet in the queue gets dropped to make room, but only if the incoming packet has higher priority. If the incoming packet is lower than everything already waiting, it gets dropped instead 💀.

Without SKB priority queue, you have to slap length limits on each individual sub-queue, and there's no easy way to set one global limit across all priorities. SKBprio is the main character here: it enforces a global queue length limit and doesn't restrict the length of individual sub-queues 💅.

SKB Priority Queue doesn't care how skb->priority gets assigned 🤷‍♀️. A super common move is to copy the 6-bit DS field of IPv4 and IPv6 packets using tc-skbedit(8). Quick note: if skb->priority is greater than or equal to 64, it's treated as 63. Anything less than 64 is taken at face value 💜.

This is how routers can locally decide which packets to drop under a DoS attack 🫶. The idea is that priorities get assigned so the higher the priority, the more expected behavior a source shows. That gives sources a reason to play by the rules, periodt ✨.

🎀 ALGORITHM 🎀

Skbprio keeps 64 lists, one for each priority from 0 to 63 🌈. When a packet gets enqueued, it goes at the tail of its priority list. When a packet is ready to head out to the network, it's pulled from the head of the highest priority list 🚀.

When the queue is full, the packet at the tail of the lowest priority list gets dropped to make room for the ingress packet, if the ingress packet is higher priority. Otherwise, the ingress packet is the one that gets dropped 😭.

The vibe is that high priority packets get as much bandwidth as possible, and low priority packets only get serviced when there's enough bandwidth left over 👑.

🍓 PARAMETERS 🍓

• limit — the maximum queue size, measured in packets. It defaults to 64. The valid range is [0, UINT32_MAX] 💖.

🦋 SEE ALSO 🦋

tc-prio(8), tc-skbedit(8) ✨

👩‍💻 AUTHORS 👩‍💻

Nishanth Devarajan <devarajn@uci.edu>, Michel Machado <michel@digirati.com.br> 🫶

This manpage is maintained by Bert Hubert <ahu@ds9a.nl> 💜

Okay that's the whole tea, bestie 🍵💅 this was an iproute2 page, last updated 13 August 2018. Stay iconic, stay Linux-literate 🌸🎀