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Library Operating System for Linux #netdev01
This document introduces a library operating system approach for using the Linux network stack in userspace. Some key points:- It describes building the Linux network stack (including components like ARP, TCP/IP, Qdisc, etc) as a library that can be loaded and used in userspace. - This allows flexible experimentation with and testing of new network stack ideas without modifying the kernel. Code can be added and tested through the library interface. - Implementations described include directly executing the code (DCE) and using it to integrate with a network simulator, as well as a Network Stack in Userspace (NUSE) that provides a full-featured POSIX-like platform for the network stack in user
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Presentation on library operating systems using the Linux network stack by Tazaki et al., highlighting its significance.
Explores reasons for using kernel space, including historical context and benefits like network stack personalization.
Discussion on various userspace network stacks and their evolution, including motivations and insights.
Raises important questions regarding benefits and adaptations needed for utilizing matured network stacks.
Proposes using the Linux network stack directly as a userspace library, hinting at practical applications.
Overview of the talk focused on introducing a library operating system for Linux and its implementation.
Design overview explaining hardware-independent architecture with three main components: host backend, kernel layer, and POSIX layer.
Examples of kernel glue and POSIX glue code, demonstrating the integration between userspace applications and kernel functionalities.
Details the implementations involving Direct Code Execution (DCE) and their networking platform benefits.
Explains ns-3 integration of network simulations with deterministic scheduling and network stack control.
Describes a userspace network stack running on Linux, emphasizing personalization and comprehensive features.
Demonstrates the execution process of the userspace network stack with an example using 'ping' command.
Illustrates scenarios where NUSE provides network stack personalization benefiting specific applications.
Outline of the workflow for writing and testing patches within the network stack development.
Discussion on continuous integration processes used for network stack testing and validation.
Details the stepwise approach for writing patches and creating test scenarios using ns-3.
Presents performance metrics of NUSE under various configurations, particularly in high-speed Ethernet environments.
Describes the setup used for measuring NUSE performance across different hardware and software configurations.
Detailed performance metrics of NUSE involving throughput and RTT analysis across various configurations.
Compares NUSE to other alternatives such as UML, containers, and scratch-based network stacks.
Highlights limitations encountered with ad-hoc kernel glues and performance issues in NUSE.
Summarizes the advantages of using a library operating system while planning future developments.
Provides links to GitHub repository and relevant resources for accessing the system discussed.
Contains ancillary materials or backup information related to the presentation subject.
Demonstrates how to utilize debugging tools to ensure proper functionality of network nodes.
Discusses the use of tools like Valgrind for memory error detection in the context of network stacks.
Instructions for configuring and building a kernel source tree tailored for NUSE.
Explains how timers function within the context of the userspace networking stack.
Presents the call graphs for network transmission and reception processes within the userspace framework.
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Library Operating System for Linux #netdev01
- 1.Library OperatingSystem withMainlineLinux Network Stack!Hajime Tazaki, Ryo Nakamura, Yuji Sekiyanetdev0.1, Feb. 2015
- 2.MotivationWhy kernel space?Packets were expensive in 1970’Why not userspace ?well grown in decades, costs degradesobtain network stack personalizationcontrollable by userspace utilities2
- 3.Userspace network stacksAlot of userspace network stackfull scratch: mTCP, Mirage, lwIPPorting: OSv, Sandstorm, libuinet (FreeBSD),Arrakis (lwIP), OpenOnload (lwIP?) Motivated by their own problems (specialized NIC,cloud, high-speed Apps)Writing a network stack is 1-week DIY,but writing opera-table network stack is decadesDIY (which is not DIY)3
- 4.QuestionsHow to benefitmatured network stackin userspace ?How to trivially introduce your ideaon network stack ?xxTCP, IPvX, etc..How to flexibly test your code with acomplex scenario ?4
- 5.The answersUsing Linuxnetwork stack as-is!as a userspace Library (libraryoperating system)5
- 6.This talk isaboutan introduction of a libraryoperating system for Linuxand its implementationwith a couple of useful use cases6
- 7.Outlook (design)hardware-independent arch(arch/lib)3 componentsHost backend layerKernel layerPOSIX layer7https://github.com/libos-nuse/net-next-nuse
- 8.Outlook (cont’d)8ARPQdiscTCP UDPDCCP SCTPICMP IPv4IPv6NetlinkBridgingNetfilterIPSec TunnelingKernel layerHost backend layerbottom halves/rcu/timer/interruptstructnet_deviceschedulernetdevclocksourcePOSIX glue layerApplication1) Build Linux srctreew/ glues as a library2) put backend!(vNIC, clock source,!scheduler) and bind3) add POSIX glue code4) applicationsmagically runs
- 9.Kernel glue code9https://github.com/libos-nuse/net-next-nuse/blob/nuse/arch/lib/sched.cvoidschedule(void)!{!! lib_task_wait();!}!signed long schedule_timeout(signed long timeout)!{!! u64 ns;!! struct SimTask *self;!!! if (timeout == MAX_SCHEDULE_TIMEOUT) {!! ! lib_task_wait();!! ! return MAX_SCHEDULE_TIMEOUT;!! }!! lib_assert(timeout >= 0);!! ns = ((__u64)timeout) * (1000000000 / HZ);!! self = lib_task_current();!! lib_event_schedule_ns(ns, &trampoline, self);!! lib_task_wait();!! /* we know that we are always perfectly on time. */!! return 0;!}
- 10.POSIX glue code10https://github.com/libos-nuse/net-next-nuse/blob/nuse/arch/lib/nuse-glue.cintnuse_socket(int domain, int type, int protocol)!{!! lib_update_jiffies();!! struct socket *kernel_socket = malloc(sizeof(struct socket));!! int ret, real_fd;!!! memset(kernel_socket, 0, sizeof(struct socket));!! ret = lib_sock_socket(domain, type, protocol, &kernel_socket);!! if (ret < 0)!! ! errno = -ret;!(snip)!! lib_softirq_wakeup();!! return real_fd;!}!weak_alias(nuse_socket, socket);
- 11.Implementations(Instances)Direct Code Execution(DCE)network simulator integration (ns-3)for more testingNetwork Stack in Userspace (NUSE)gives new platform of Linux network stackfor ad-hoc network stack11
- 12.Direct Code Executionns-3integrationdeterministic schedulersingle-process model virtualizationdlmopen(3)-like virtualizationfull control over multiple network stacks12
- 13.Execution (DCE)main() =>dlmopen(ping,liblinux.so) => main()=>socket(2)=>dce_socket() => (do whatever)13
- 14.
- 15.
- 16.Network Stack inUserspaceUserspacenetwork stack running onLinux (POSIX) platformNetwork stack personalizationFull features by design (full stack)ARP/ND, UDP/TCP (all cc algorithm), SCTP,DCCP, QDISC, XFRM, netfilter, etc.16
- 17.17ApplicationARPQdiscTCP UDP DCCPSCTPICMP IPv4IPv6NetlinkBridgingNetfilterIPSec TunnelingKernel layerHost backend layer (NUSE)POSIX glue layerbottom halves/rcu/timer/interruptstructnet_deviceRAW DPDK netmap ...NICschedulernetdevclocksourcesystem call hijackApplicationmaster process slave processesrumpsyscallproxyrumpserver
- 18.Execution (NUSE)LD_PRELOAD=libnuse-linux.so pingwww.google.comping(8) => socket(2) => nuse_socket()=> raw(7) => (network)18
- 19.When it’s useful?ad-hocnetwork stack (network stackpersonalization)LD_PRELOAD=liblinux-mptcp.so firefoxBundle with kernel bypassesIntel DPDK / netmap / PF_RING / etc.debugging/testing with ns-319
- 20.Testing workflow1.Write/modify code(patches)2.Write a test code (incl. packetexchanges)3.if PASS; accept pull-request else; rejects20
- 21.
- 22.T1) write apatch22Fixes: de3b7a06dfe1 ("xfrm6: Fix transport header offset in _decode_session6.")!Signed-off-by: Hajime Tazaki <tazaki@sfc.wide.ad.jp>!---!net/ipv6/xfrm6_policy.c | 1 +!1 file changed, 1 insertion(+)!!diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c!index 48bf5a0..8d2d01b 100644!--- a/net/ipv6/xfrm6_policy.c!+++ b/net/ipv6/xfrm6_policy.c!@@ -200,6 +200,7 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, intreverse)!!#if IS_ENABLED(CONFIG_IPV6_MIP6)!! ! case IPPROTO_MH:!+! ! ! offset += ipv6_optlen(exthdr);!! ! ! if (!onlyproto && pskb_may_pull(skb, nh + offset + 3 - skb->data)) {!! ! ! ! struct ip6_mh *mh;!http://patchwork.ozlabs.org/patch/436351/
- 23.T2) write atestAs ns-3 scenarioC++ or pythoncreate a topologyconfig nodesrun/check results(e.g., ping6)23+-----------+!| HA |!+-----------+!|sim0!+----------+------------+!|sim0 |sim0!sim2+----+---+ +----+---+!- - -| AR1 | | AR2 |!+---+----+ +----+---+!|sim1 |sim1!| |!sim0 sim0!+----+------+ (Movement) +----+-----+!| MR | <=====> | MR |!+-----------+ +----------+!|sim1 |sim1!+---------+ +---------+!| MNN | | MNN |!+---------+ +---------+!http://code.nsnam.org/thehajime/ns-3-dce-umip/file/tip/test/dce-umip-test.cc
- 24.24#!/usr/bin/python!!from ns.dce import*!from ns.core import *!!nodes = NodeContainer()!nodes.Create (100)!dce = DceManagerHelper()!dce.SetNetworkStack ("liblinux.so")!dce.Install (nodes)!!app = DceApplicationHelper()!app.SetBinary ("ping6")!app.Install (nodes)!(snip)!!NS_TEST_ASSERT_MSG_EQ (m_pingStatus, true, "Umip test " << m_testname!<< " did not return successfully: " << g_testError)!!Simulator.Stop (Seconds(1000.0))!Simulator.Run ()
- 25.Performance of NUSE10GEthernet back-to-backtransmissionIP forwardingnative Linux, raw socket, tap, dpdk,netmap25
- 26.Performance: setup2610G10GNUSE nodeTx/Rx nodesCPUXeon E5-2650v2 @ 2.60GHz (16 core)Xeon L3426 @ 1.87GHz (8 core)Memory 32GB 4GBNIC Intel X520 Intel X520OShost:3.13.0-32nuse: 3.17.0-rc1host:3.13.0-32ping!flowgenvnstat!(packet count)Tx NUSE Rxping!flowgen
- 27.Host Tx27RxNUSEping (RTT)throughput(1024byte,UDP)0100020003000400050006000dpdknative netmap raw tapThroughput(Mbps)00.20.40.60.81dpdk native netmap raw tapRTT(ms)native: ping A.B.C.D!others: ./nuse ping A.B.C.D
- 28.L3 RoutingSender->NUSE->Receiver28Tx RxNUSEping(RTT)throughput(1024byte,UDP)0100020003000400050006000dpdk native netmap raw tapThroughput(Mbps)00.20.40.60.81dpdk native netmap raw tapRTT(ms)
- 29.AlternativesUML/LKL (1proc/1vm, noPOSIX i/f)Containers (can’t change kernel)scratch-based (mTCP,Mirage)rumpkernel (in NetBSD)29
- 30.Limitationsad-hoc kernel gluesrequiredwhen we changed a member of a struct,LibOS needs to follow itPerformance drawbacks on NUSEadapt known techniques (mTCP)30
- 31.(not) ConclusionsAn abstractionfor multiple benefitsConservativeUse past decades effort as muchwith a small amount of effortPlaning to RFC for upstreaming31
- 32.
- 33.
- 34.Bug reproducibility34Wi-Fi Wi-FiHomeAgentAP1 AP2handoffping6mobile nodecorrespondentnode(gdb) b mip6_mh_filter if dce_debug_nodeid()==0 Breakpoint 1 at 0x7ffff287c569: file net/ipv6/mip6.c, line 88.<continue>(gdb) bt 4#0 mip6_mh_filter(sk=0x7ffff7f69e10, skb=0x7ffff7cde8b0)at net/ipv6/mip6.c:109 #1 0x00007ffff2831418 in ipv6_raw_deliver(skb=0x7ffff7cde8b0, nexthdr=135) at net/ipv6/raw.c:199 #2 0x00007ffff2831697 in raw6_local_deliver(skb=0x7ffff7cde8b0, nexthdr=135) at net/ipv6/raw.c:232 #3 0x00007ffff27e6068 in ip6_input_finish(skb=0x7ffff7cde8b0) at net/ipv6/ip6_input.c:197
- 35.DebuggingMemory error detectionamongdistributed nodesin a single processusing Valgrind!!35==5864== Memcheck, a memory error detector==5864== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.==5864== UsingValgrind-3.6.0.SVN and LibVEX; rerun with -h for copyright in==5864== Command: ../build/bin/ns3test-dce-vdl --verbose==5864== ==5864== Conditional jump or move depends on uninitialised value(s)==5864== at 0x7D5AE32: tcp_parse_options (tcp_input.c:3782)==5864== by 0x7D65DCB: tcp_check_req (tcp_minisocks.c:532)==5864== by 0x7D63B09: tcp_v4_hnd_req (tcp_ipv4.c:1496)==5864== by 0x7D63CB4: tcp_v4_do_rcv (tcp_ipv4.c:1576)==5864== by 0x7D6439C: tcp_v4_rcv (tcp_ipv4.c:1696)==5864== by 0x7D447CC: ip_local_deliver_finish (ip_input.c:226)==5864== by 0x7D442E4: ip_rcv_finish (dst.h:318)==5864== by 0x7D2313F: process_backlog (dev.c:3368)==5864== by 0x7D23455: net_rx_action (dev.c:3526)==5864== by 0x7CF2477: do_softirq (softirq.c:65)==5864== by 0x7CF2544: softirq_task_function (softirq.c:21)==5864== by 0x4FA2BE1: ns3::TaskManager::Trampoline(void*) (task-manage==5864== Uninitialised value was created by a stack allocation==5864== at 0x7D65B30: tcp_check_req (tcp_minisocks.c:522)==5864==
- 36.Fine-grained parameter coverage36Codecoverage measurement with DCEWith fine-grained network, node, protocol parameters
- 37.1) kernel buildbuildkernel source tree w/ the patchmake menuconfig ARCH=simmake library ARCH=sim➔ libnuse-linux-3.17-rc1.so37
- 38.Example: How timerworks38add_timer()TIMER_SOFTIRQtimer_listrun_timer_softirq()timer handlertimer thread(timer_create (2))
- 39.Tx callgraph39sendmsg ()(socket API)lib_sock_sendmsg () (NUSE)sock_sendmsg ()ip_send_skb ()ip_finish_output2 ()dst_neigh_output () (existingneigh_resolve_output () -kernel)arp_solicit ()dev_queue_xmit ()lib_dev_xmit () (NUSE)nuse_vif_raw_write ()
- 40.start_thread () (pthread)nuse_netdev_rx_trampoline()nuse_vif_raw_read () (NUSE)lib_dev_rx ()netif_rx () (ex-kernel)Rx callgraph40start_thread () (pthread)do_softirq () (NUSE)net_rx_action ()process_backlog () (ex-kernel)__netif_receive_skb_core ()ip_rcv ()vNIC!rxsoftirq!rx