BERKELEY PACKET FILTER: Theory, Practice and Perspectives
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Improving Route Scalability: Nexthops As Separate Objects
Improving Route Scalability: Nexthops as Separate Objects September 2019 David Ahern | Cumulus Networks !1 Agenda Executive Summary ▪ If you remember nothing else about this talk … Driving use case Review legacy route API Dive into Nexthop API Benefits of the new API Cumulus Networks !2 Performance with the Legacy Route API route route route prefix/lenroute prefix/lendev prefix/lendev gatewayprefix/len gatewaydev gatewaydev gateway Cumulus Networks !3 Splitting Next Hops from Routes Routes with separate Nexthop objects Legacy Route API route route prefix/len nexthop route nexthop id dev route gateway prefix/lenroute prefix/lendev prefix/lendev gatewayprefix/len gatewaydev gatewaydev gateway route prefix/len nexthop nexthop nexthop id group nexthopdev nexthop[N] gatewaydev gateway Cumulus Networks !4 Dramatically Improves Route Scalability … Cumulus Networks !5 … with the Potential for Constant Insert Times Cumulus Networks !6 Networking Operating System Using Linux APIs Routing daemon or utility manages switchd ip FRR entries in kernel FIBs via rtnetlink APIs SDK userspace ▪ Enables other control plane software to use Linux networking APIs rtnetlink Data path connections, stats, troubleshooting, … FIB notifications FIB Management of hardware offload is separate kernel upper devices tunnels ▪ Keeps hardware in sync with kernel ... eth0 swp1 swp2 swpN Userspace driver with SDK leveraging driver driver driver kernel notifications NIC switch ASIC H / W Cumulus Networks !7 NOS with switchdev Driver In-kernel switchdev driver ip FRR Leverages -
The Kernel Report
The kernel report (ELC 2012 edition) Jonathan Corbet LWN.net [email protected] The Plan Look at a year's worth of kernel work ...with an eye toward the future Starting off 2011 2.6.37 released - January 4, 2011 11,446 changes, 1,276 developers VFS scalability work (inode_lock removal) Block I/O bandwidth controller PPTP support Basic pNFS support Wakeup sources What have we done since then? Since 2.6.37: Five kernel releases have been made 59,000 changes have been merged 3069 developers have contributed to the kernel 416 companies have supported kernel development February As you can see in these posts, Ralink is sending patches for the upstream rt2x00 driver for their new chipsets, and not just dumping a huge, stand-alone tarball driver on the community, as they have done in the past. This shows a huge willingness to learn how to deal with the kernel community, and they should be strongly encouraged and praised for this major change in attitude. – Greg Kroah-Hartman, February 9 Employer contributions 2.6.38-3.2 Volunteers 13.9% Wolfson Micro 1.7% Red Hat 10.9% Samsung 1.6% Intel 7.3% Google 1.6% unknown 6.9% Oracle 1.5% Novell 4.0% Microsoft 1.4% IBM 3.6% AMD 1.3% TI 3.4% Freescale 1.3% Broadcom 3.1% Fujitsu 1.1% consultants 2.2% Atheros 1.1% Nokia 1.8% Wind River 1.0% Also in February Red Hat stops releasing individual kernel patches March 2.6.38 released – March 14, 2011 (9,577 changes from 1198 developers) Per-session group scheduling dcache scalability patch set Transmit packet steering Transparent huge pages Hierarchical block I/O bandwidth controller Somebody needs to get a grip in the ARM community. -
TCPDUMP Caution
TCPDUMP q Refer to book ”Open Source Network Administration” m Online sample chapter: http://www.phptr.com/articles/article.asp?p=170902&seqNum=4 q Some tools are not based directly on the data being transmitted on a network, but information related to that data. m For example, network bandwidth values m System logs on network equipment q Sometimes needs to examine the packets themselves. m Diagnose some particularly tricky network problems q Widely used open source tool for directly analyzing packets: tcpdump m http://www.tcpdump.org/ Network Analyzer 1-1 Caution q Before you use tcpdump or other analyzer: m Will be able to see some private data m Consult/research Legal implication first m Respect the privacy of other users Network Analyzer 1-2 1 What Tcpdump can do for you q View the entire data portion of an Ethernet frame or other link layer protocol m An IP packet m An ARP packet m Or any protocol at a higher layer than Ethernet. q Very useful m Tcpdump is to a network administrator like a microscope to a biologist. m Give a very clear picture of a specific part of your network m Can be used when the problem is simply that something is not working properly. Network Analyzer 1-3 What tcpdump can do for you? q Case1 : Web browser can not load pages from a server – it hangs. m Problem with client? Server? Or between? m Run tcpdump while loading • Watch every stage to see the following – DNS query – HTTP request to server – Server respond q Case 2: help debug denial of service attacks. -
Rootless Containers with Podman and Fuse-Overlayfs
CernVM Workshop 2019 (4th June 2019) Rootless containers with Podman and fuse-overlayfs Giuseppe Scrivano @gscrivano Introduction 2 Rootless Containers • “Rootless containers refers to the ability for an unprivileged user (i.e. non-root user) to create, run and otherwise manage containers.” (https://rootlesscontaine.rs/ ) • Not just about running the container payload as an unprivileged user • Container runtime runs also as an unprivileged user 3 Don’t confuse with... • sudo podman run --user foo – Executes the process in the container as non-root – Podman and the OCI runtime still running as root • USER instruction in Dockerfile – same as above – Notably you can’t RUN dnf install ... 4 Don’t confuse with... • podman run --uidmap – Execute containers as a non-root user, using user namespaces – Most similar to rootless containers, but still requires podman and runc to run as root 5 Motivation of Rootless Containers • To mitigate potential vulnerability of container runtimes • To allow users of shared machines (e.g. HPC) to run containers without the risk of breaking other users environments • To isolate nested containers 6 Caveat: Not a panacea • Although rootless containers could mitigate these vulnerabilities, it is not a panacea , especially it is powerless against kernel (and hardware) vulnerabilities – CVE 2013-1858, CVE-2015-1328, CVE-2018-18955 • Castle approach : it should be used in conjunction with other security layers such as seccomp and SELinux 7 Podman 8 Rootless Podman Podman is a daemon-less alternative to Docker • $ alias -
Studying the Real World Today's Topics
Studying the real world Today's topics Free and open source software (FOSS) What is it, who uses it, history Making the most of other people's software Learning from, using, and contributing Learning about your own system Using tools to understand software without source Free and open source software Access to source code Free = freedom to use, modify, copy Some potential benefits Can build for different platforms and needs Development driven by community Different perspectives and ideas More people looking at the code for bugs/security issues Structure Volunteers, sponsored by companies Generally anyone can propose ideas and submit code Different structures in charge of what features/code gets in Free and open source software Tons of FOSS out there Nearly everything on myth Desktop applications (Firefox, Chromium, LibreOffice) Programming tools (compilers, libraries, IDEs) Servers (Apache web server, MySQL) Many companies contribute to FOSS Android core Apple Darwin Microsoft .NET A brief history of FOSS 1960s: Software distributed with hardware Source included, users could fix bugs 1970s: Start of software licensing 1974: Software is copyrightable 1975: First license for UNIX sold 1980s: Popularity of closed-source software Software valued independent of hardware Richard Stallman Started the free software movement (1983) The GNU project GNU = GNU's Not Unix An operating system with unix-like interface GNU General Public License Free software: users have access to source, can modify and redistribute Must share modifications under same -
I3: Maximizing Packet Capture Performance
I3: Maximizing Packet Capture Performance Andrew Brown Agenda • Why do captures drop packets, how can you tell? • Software considerations • Hardware considerations • Potential hardware improvements • Test configurations/parameters • Performance results Sharkfest 2014 What is a drop? • Failure to capture a packet that is part of the traffic in which you’re interested • Dropped packets tend to be the most important • Capture filter will not necessarily help Sharkfest 2014 Why do drops occur? • Applications don’t know that their data is being captured • Result: Only one chance to capture a packet • What can go wrong? Let’s look at the life of a packet Sharkfest 2014 Internal packet flow • Path of a packet from NIC to application (Linux) • Switch output queue drops • Interface drops • Kernel drops Sharkfest 2014 Identifying drops • Software reports drops • L4 indicators (TCP ACKed lost segment) • L7 indicators (app-level sequence numbers revealed by dissector) Sharkfest 2014 When is (and isn’t) it necessary to take steps to maximize capture performance? • Not typically necessary when capturing traffic of <= 1G end device • More commonly necessary when capturing uplink traffic from a TAP or SPAN port • Some sort of action is almost always necessary at 10G • Methods described aren’t always necessary • Methods focus on free solutions Sharkfest 2014 Software considerations - Windows • Quit unnecessary programs • Avoid Wireshark for capturing ˗ Saves to TEMP ˗ Additional processing for packet statistics • Uses CPU • Uses memory over time, can lead -
Version 7.8-Systemd
Linux From Scratch Version 7.8-systemd Created by Gerard Beekmans Edited by Douglas R. Reno Linux From Scratch: Version 7.8-systemd by Created by Gerard Beekmans and Edited by Douglas R. Reno Copyright © 1999-2015 Gerard Beekmans Copyright © 1999-2015, Gerard Beekmans All rights reserved. This book is licensed under a Creative Commons License. Computer instructions may be extracted from the book under the MIT License. Linux® is a registered trademark of Linus Torvalds. Linux From Scratch - Version 7.8-systemd Table of Contents Preface .......................................................................................................................................................................... vii i. Foreword ............................................................................................................................................................. vii ii. Audience ............................................................................................................................................................ vii iii. LFS Target Architectures ................................................................................................................................ viii iv. LFS and Standards ............................................................................................................................................ ix v. Rationale for Packages in the Book .................................................................................................................... x vi. Prerequisites -
Jitk: a Trustworthy In-Kernel Interpreter Infrastructure
Jitk: A trustworthy in-kernel interpreter infrastructure Xi Wang, David Lazar, Nickolai Zeldovich, Adam Chlipala, Zachary Tatlock MIT and University of Washington Modern OSes run untrusted user code in kernel In-kernel interpreters - Seccomp: sandboxing (Linux) - BPF: packet filtering - INET_DIAG: socket monitoring - Dtrace: instrumentation Critical to overall system security - Any interpreter bugs are serious! 2/30 Many bugs have been found in interpreters Kernel space bugs - Control flow errors: incorrect jump offset, ... - Arithmetic errors: incorrect result, ... - Memory errors: buffer overflow, ... - Information leak: uninitialized read Kernel-user interface bugs - Incorrect encoding/decoding User space bugs - Incorrect input generated by tools/libraries Some have security consequences: CVE-2014-2889, ... See our paper for a case study of bugs 3/30 How to get rid of all these bugs at once? Theorem proving can help kill all these bugs seL4: provably correct microkernel [SOSP'09] CompCert: provably correct C compiler [CACM'09] This talk: Jitk - Provably correct interpreter for running untrusted user code - Drop-in replacement for Linux's seccomp - Built using Coq proof assistant + CompCert 5/30 Theorem proving: overview specification proof implementation Proof is machine-checkable: Coq proof assistant Proof: correct specification correct implementation Specification should be much simpler than implementation 6/30 Challenges What is the specification? How to translate systems properties into proofs? How to extract a running -
Mesalock Linux: Towards a Memory-Safe Linux Distribution
MesaLock Linux Towards a memory-safe Linux distribution Mingshen Sun MesaLock Linux Maintainer | Baidu X-Lab, USA Shanghai Jiao Tong University, 2018 whoami • Senior Security Research in Baidu X-Lab, Baidu USA • PhD, The Chinese University of Hong Kong • System security, mobile security, IoT security, and car hacking • MesaLock Linux, TaintART, Pass for iOS, etc. • mssun @ GitHub | https://mssun.me !2 MesaLock Linux • Why • What • How !3 Why • Memory corruption occurs in a computer program when the contents of a memory location are unintentionally modified; this is termed violating memory safety. • Memory safety is the state of being protected from various software bugs and security vulnerabilities when dealing with memory access, such as buffer overflows and dangling pointers. !4 Stack Buffer Overflow • https://youtu.be/T03idxny9jE !5 Types of memory errors • Access errors • Buffer overflow • Race condition • Use after free • Uninitialized variables • Memory leak • Double free !6 Memory-safety in user space • CVE-2017-13089 wget: Stack-based buffer overflow in HTTP protocol handling • A stack-based buffer overflow when processing chunked, encoded HTTP responses was found in wget. By tricking an unsuspecting user into connecting to a malicious HTTP server, an attacker could exploit this flaw to potentially execute arbitrary code. • https://bugzilla.redhat.com/show_bug.cgi?id=1505444 • POC: https://github.com/r1b/CVE-2017-13089 !7 What • Linux distribution • Memory-safe user space !8 Linux Distribution • A Linux distribution (often abbreviated as distro) is an operating system made from a software collection, which is based upon the Linux kernel and, often, a package management system. !9 Linux Distros • Server: CentOS, Federa, RedHat, Debian • Desktop: Ubuntu • Mobile: Android • Embedded: OpenWRT, Yocto • Hard-core: Arch Linux, Gentoo • Misc: ChromeOS, Alpine Linux !10 Security and Safety? • Gentoo Hardened: enables several risk-mitigating options in the toolchain, supports PaX, grSecurity, SELinux, TPE and more. -
Chapter 1. Origins of Mac OS X
1 Chapter 1. Origins of Mac OS X "Most ideas come from previous ideas." Alan Curtis Kay The Mac OS X operating system represents a rather successful coming together of paradigms, ideologies, and technologies that have often resisted each other in the past. A good example is the cordial relationship that exists between the command-line and graphical interfaces in Mac OS X. The system is a result of the trials and tribulations of Apple and NeXT, as well as their user and developer communities. Mac OS X exemplifies how a capable system can result from the direct or indirect efforts of corporations, academic and research communities, the Open Source and Free Software movements, and, of course, individuals. Apple has been around since 1976, and many accounts of its history have been told. If the story of Apple as a company is fascinating, so is the technical history of Apple's operating systems. In this chapter,[1] we will trace the history of Mac OS X, discussing several technologies whose confluence eventually led to the modern-day Apple operating system. [1] This book's accompanying web site (www.osxbook.com) provides a more detailed technical history of all of Apple's operating systems. 1 2 2 1 1.1. Apple's Quest for the[2] Operating System [2] Whereas the word "the" is used here to designate prominence and desirability, it is an interesting coincidence that "THE" was the name of a multiprogramming system described by Edsger W. Dijkstra in a 1968 paper. It was March 1988. The Macintosh had been around for four years. -
Of Mobile Devices: a Survey on Network Traffic Analysis
1 The Dark Side(-Channel) of Mobile Devices: A Survey on Network Traffic Analysis Mauro Conti, Senior Member, IEEE, QianQian Li, Alberto Maragno, and Riccardo Spolaor*, Member, IEEE. Abstract—In recent years, mobile devices (e.g., smartphones elements enable both smartphones and tablets to have the and tablets) have met an increasing commercial success and same functionalities typically offered by laptops and desktop have become a fundamental element of the everyday life for computers. billions of people all around the world. Mobile devices are used not only for traditional communication activities (e.g., voice According to the statistics reported in [1], smartphone calls and messages) but also for more advanced tasks made users were 25:3% of the global population in 2015, and this possible by an enormous amount of multi-purpose applications percentage is expected to grow till 37% in 2020. Similarly, the (e.g., finance, gaming, and shopping). As a result, those devices statistics about tablets reported in [2] indicate a global penetra- generate a significant network traffic (a consistent part of the overall Internet traffic). For this reason, the research community tion of 13:8% in 2015, expected to reach 19:2% in 2020. The has been investigating security and privacy issues that are related driving forces of this tremendous success are the ubiquitous to the network traffic generated by mobile devices, which could Internet connectivity, thanks to the worldwide deployment of be analyzed to obtain information useful for a variety of goals cellular and Wi-Fi networks, and a large number of apps (ranging from fine-grained user profiling to device security and available in the official (and unofficial) marketplaces. -
Packet Capture Procedures on Cisco Firepower Device
Packet Capture Procedures on Cisco Firepower Device Contents Introduction Prerequisites Requirements Components Used Steps to Capture Packets Copy a Pcap File Introduction This document describes how to use the tcpdump command in order to capture packets that are seen by a network interface of your Firepower device. It uses Berkeley Packet Filter (BPF) syntax. Prerequisites Requirements Cisco recommends that you have knowledge of the Cisco Firepower device and the virtual device models. Components Used This document is not restricted to specific software and hardware versions. The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command. Warning: If you run tcpdump command on a production system, it can impact network performance. Steps to Capture Packets Log in to the CLI of your Firepower device. In versions 6.1 and later, enter capture-traffic. For example, > capture-traffic Please choose domain to capture traffic from: 0 - eth0 1 - Default Inline Set (Interfaces s2p1, s2p2) In versions 6.0.x.x and earlier, enter system support capture-traffic. For example, > system support capture-traffic Please choose domain to capture traffic from: 0 - eth0 1 - Default Inline Set (Interfaces s2p1, s2p2) After you make a selection, you will be prompted for options: Please specify tcpdump options desired. (or enter '?' for a list of supported options) Options: In order to capture sufficient data from the packets, it is necessary to use the -s option in order to set the snaplength correctly.