eBPF

eBPF (sometimes referred to by the acronym BPF, standing for Berkeley Packet Filter)[2][5] is a technology that can run programs in a privileged context such as the operating system kernel.[6] It is used to safely and efficiently extend the capabilities of the kernel at runtime without requiring changes to kernel source code or loading kernel modules.[7] Safety is provided through an in-kernel verifier which performs static code analysis and rejects programs which crash, hang or otherwise interfere with the kernel negatively.[8][9] This validation model differs from sandboxed environments, where the execution environment is restricted and the runtime has no insight about the program.[10] Examples of programs that are automatically rejected are programs without strong exit guarantees (i.e. for/while loops without exit conditions) and programs dereferencing pointers without safety-checks.[11] Loaded programs which passed the verifier are either interpreted or in-kernel JIT compiled for native execution performance. The execution model is event-driven and with few exceptions run-to-completion,[2] meaning, programs can be attached to various hook points in the operating system kernel and are run upon triggering of an event. eBPF use cases include (but are not limited to) networking such as XDP, tracing and security subsystems.[6] Given eBPF's efficiency and flexibility opened up new possibilities to solve production issues, Brendan Gregg famously dubbed eBPF "superpowers for Linux".[12] Linus Torvalds said, "BPF has actually been really useful, and the real power of it is how it allows people to do specialized code that isn't enabled until asked for".[13] Due to its success in Linux, the eBPF runtime has been ported to other operating systems such as Windows.[4]

eBPF
Original author(s)Alexei Starovoitov,
Daniel Borkmann[1][2]
Developer(s)Open source community, Meta, Google, Isovalent, Microsoft, Netflix[1]
Initial release2014 (2014)[3]
RepositoryLinux: git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
Windows: github.com/Microsoft/ebpf-for-windows/
Written inC
Operating systemLinux, Windows[4]
TypeRuntime system
LicenseLinux: GPL
Windows: MIT License
Websiteebpf.io

History

Evolution from classic BPF

eBPF was built on top of the Berkeley Packet Filter (cBPF). At the lowest level, it introduced the use of ten 64-bit registers (instead of two 32-bit long registers for cBPF), different jump semantics, a call instruction and corresponding register passing convention, new instructions, and a different encoding for these instructions.[14]

Most significant milestones in the evolution of eBPF
DateEvent
April 2011The first in-kernel Linux JIT compiler for the classic Berkeley Packet Filter got merged.[15]
January 2012The first non-networking use case of the classic Berkeley Packet Filter, seccomp-bpf,[16] appeared; it allows filtering of system calls using a configurable policy implemented through BPF instructions.
March 2014David S. Miller, primary maintainer of the Linux networking stack, accepted the rework of the old in-kernel BPF interpreter. It was replaced by an eBPF interpreter and the Linux kernel internally translates classic BPF (cBPF) into eBPF instructions.[17]
March 2015The ability to attach eBPF to kprobes as first tracing use case was merged.[19] In the same month, initial infrastructure work got accepted to attach eBPF to the networking traffic control (tc) layer allowing to attach eBPF to the core ingress and later also egress paths of the network stack, later heavily used by projects such as Cilium.[20][21][22]
August 2015The eBPF compiler backend got merged into LLVM 3.7.0 release.[23]
September 2015Brendan Gregg announced a collection of new eBPF-based tracing tools as the bcc project, providing a front-end for eBPF to make it easier to write programs.[24]
July 2016eBPF got the ability to be attached into network driver's core receive path. This layer is known today as eXpress DataPath (XDP) and was added as a response to DPDK to create a fast data path which works in combination with the Linux kernel rather than bypassing it.[25][26][27]
August 2016Cilium was initially announced during LinuxCon as a project providing fast IPv6 container networking with eBPF and XDP. Today, Cilium has been adopted by major cloud provider's Kubernetes offerings and is one of the most widely used CNIs.[28][22][29]
November 2016Netronome added offload of eBPF programs for XDP and tc BPF layer to their NIC.[30]
May 2017Meta's layer 4 load-balancer, Katran, went live. Every packet towards facebook.com since then has been processed by eBPF & XDP.[31]
November 2017eBPF becomes its own kernel subsystem to ease the continuously growing kernel patch management. The first pull request by eBPF maintainers was submitted.[32]
September 2017Bpftool was added to the Linux kernel as a user space utility to introspect the eBPF subsystem.[33]
January 2018A new socket family called AF_XDP was published, allowing for high performance packet processing with zero-copy semantics at the XDP layer.[34] Today, DPDK has an official AF_XDP poll-mode driver support.[35]
February 2018The bpfilter prototype has been published, allowing translation of a subset of iptables rulesets into eBPF via a newly developed user mode driver. The work has caused controversies due to the ongoing nftables development effort and has not been merged into mainline.[36][37]
October 2018The new bpftrace tool has been announced by Brendan Gregg as DTrace 2.0 for Linux.[38]
November 2018eBPF introspection has been added for kTLS in order to support the ability for in-kernel TLS policy enforcement.[39]
November 2018BTF (BPF Type Format) has been added to the Linux kernel as an efficient meta data format which is approximately 100x smaller in size than DWARF.[40]
December 2019The first 880-page long book on BPF, written by Brendan Gregg, was released.[41]
March 2020Google upstreamed BPF LSM support into the Linux kernel, enabling programmable LSMs through eBPF.[42]
September 2020The eBPF compiler backend for GCC was merged.[43]

Adoption

eBPF has been adopted by a number of large-scale production users, for example:

The bee is the official logo for eBPF. At the first eBPF Summit there was a vote taken and the bee mascot was named "eBee".[78][79] The logo has originally been created by Vadim Shchekoldin.[79] Earlier unofficial eBPF mascots have existed in the past,[80] but haven't seen widespread adoption.

Naming

There has been controversy around the naming of eBPF. The alias eBPF is often interchangeably used with BPF, for example by the Linux kernel community. eBPF and BPF is referred to as a technology name like LLVM.[2] eBPF evolved from the Berkeley Packet Filter as an extended version, but its use case outgrew networking, and today eBPF as a pseudo-acronym is preferred.[2]

eBPF Foundation

The eBPF Foundation was created in August 2021 with the goal to expand the contributions being made to extend the powerful capabilities of eBPF and grow beyond Linux.[1] Founding members include Meta, Google, Isovalent, Microsoft and Netflix. The purpose is to raise, budget and spend funds in support of various open source, open data and/or open standards projects relating to eBPF technologies[81] to further drive the growth and adoption of the eBPF ecosystem. Since inception, Red Hat, Huawei, Crowdstrike, Tigera, DaoCloud, Datoms, FutureWei also joined.[82]

Security concerns

Due to the ease of programmability, eBPF has been used as a tool for implementing microarchitectural timing side-channel attacks such as Spectre against vulnerable microprocessors.[83] While unprivileged eBPF implemented mitigations against transient execution attacks,[84] unprivileged use has ultimately been disabled by the kernel community by default to protect from use against future hardware vulnerabilities.[85]

Conferences

The eBPF community organises a number of technical workshops and conferences to discuss ongoing research, development efforts, and use cases around eBPF. They can broadly be categorised into user-focused conferences and more developer-focused conferences.

User-focused conferences:

Developer-focused conferences:

See also

References
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  2. "BPF Internals". USENIX LISA 2021 conference. 1 June 2021. Retrieved 1 July 2022.
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  4. "Making eBPF work on Windows". Microsoft Open Source Blog. 10 May 2021. Retrieved 1 July 2022.
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Further reading
  • Gregg, Brendan (December 2019). BPF Performance Tools. Addison-Wesley. ISBN 978-0136554820.
  • David Calavera, Lorenzo Fontana (December 2019). Linux Observability With BPF. O'Reilly Media, Incorporated. ISBN 978-1492050209.
  • Gregg, Brendan (December 2020). Systems Performance, Second edition. ISBN 978-0136820154.
  • Rice, Liz (April 2022). What Is eBPF?. ISBN 978-1492097259.
  • Rice, Liz (April 2023). Learning eBPF: Programming the Linux Kernel for Enhanced Observability, Networking, and Security. O'Reilly Media. ISBN 978-1098135126.
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