The document discusses using dlmopen to run the same binary multiple times in separate namespaces on a single machine. This allows debugging applications with many nodes by loading the binary independently for each node. It also explores using dlmopen to run network stack code in a virtualized environment for network simulation.

1. dlmopen(3C)をつかった VM
たざき はじめ (@thehajime)
カーネル/VM探検隊
2013/12/8

2. デモ
2

3. dlmopen とは?
• dlmopen(3)
dlopenの亜種
•
• link map ID (lmid)で名前空間分離
• 2006年以降誰もいじってない
3

4. なぜに dlmopen ?
• これ全部VMであげたい!
• fs.inotify.max_user_instances =
128 (LXCの場合)
• loadavgが30とか
• 必要なのはネットワーク部分だ
けなのに。。
4

5. なぜに dlmopen ?
• ノードまたがるデバッ
グ。。
• 1、2台ならまだ余裕
• 30台で動くアプリを gdb と
か無理。。。
5

6. なぜに dlmopen ?
• dlmopenで同一 ELF バイナリを複数回load
• lmid (Link-map ID)を別にする
• global変数はぶつかるよ?
• 退避
• IPアドレスとか、ノード間で違う情報は?
• ネットワークスタックも別にする
6

7. Direct Code Execution
でぃれくと こーど えぐじぇきゅーじょん
• ns-3 (ネットワークシミュレータ)の拡張
• カーネルコードはネットワーク部のみ利用
• ファイルシステム無： chrootなディレクトリを割当
• /proc もなし(sysctl ライクな口と一部familyのsocketのみ)
• LKMも今は使えず
• struct net_device <=> ns3::NetDevice
• jiffies <=> ns3::Time (仮想クロック)
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8. どうやって動く ?
#!/usr/bin/python
from ns.dce import *
from ns.core import *
• main (ns-3 シナリオ)
• PIEバイナリを dlmopen
• 必要なsyscall/libcallを上書き
•
nodes = NodeContainer()
nodes.Create (100)
dce = DceManagerHelper()
dce.SetNetworkStack ("liblinux.so");
dce.Install (nodes);
(weak_alias)
カーネル突入部は liblinux.so へ
リダイレクト
app = DceApplicationHelper()
app.SetBinary ("ospfd")
app.Install (nodes)
Simulator.Stop (Seconds(1000.0))
Simulator.Run ()
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9. liblinux.so
Application
(ip, iptables, quagga)
POSIX layer
•
カーネルソースを
sharedでビルド
DCE
TCP UDP
Heap
Stack
ICMP
•
ARP
Netfilter
memory
Netlink
arch/simにglueコード
DCCP
Virtualization Core
layer
IPv6
Qdisc
IPSec
struct net_device
SCTP
IPv4
Bridging
struct
net_device
jiffies/
gettimeofday()
Tunneling
bottom halves/rcu/
timer/interrupt
Synchronize
Kernel layer
ns3::NetDevice
network simulation core
9
Simulated
Clock

10. rump (netbsd)
BSD
Stack
glue
apps
(gdb) bt
#0 rumpcomp_sockin_sendmsg (s=7, msg=0x703010, flags=0, snd=0x7ffffffed178) at buildrump.sh/src/sys/rump/net/lib/
rumpcomp_user.c:426
#1 0x00007ffff7df8526 in sockin_usrreq (so=so@entry=0x6fedb0, req=req@entry=9, m=0x6cce00, nam=nam@entry=
control=control@entry=0x0, l=<optimized out>) at buildrump.sh/src/sys/rump/net/lib/libsockin/sockin.c:510
#2 0x00007ffff7be4e79 in sosend (so=0x6fedb0, addr=0x0, uio=0x7ffffffed500, top=0x6cce00, control=0x0, flags=0, l=0x
at /home/tazaki/gitworks/buildrump.sh/src/lib/librumpnet/../../sys/rump/../kern/uipc_socket.c:1048
#3 0x00007ffff7be7b4c in soo_write (fp=<optimized out>, offset=<optimized out>, uio=0x7ffffffed500, cred=<optimize
flags=<optimized out>) at /home/tazaki/gitworks/buildrump.sh/src/lib/librumpnet/../../sys/rump/../kern/sys_socket.c:11
#4 0x00007ffff788f620 in dofilewrite (fd=fd@entry=3, fp=0x6f8e80, buf=0x400e88, nbyte=37, offset=0x6f8e80, flags=fla
retval=retval@entry=0x7ffffffed5e0) at /home/tazaki/gitworks/buildrump.sh/src/lib/librump/../../sys/rump/../kern/sys_g
#5 0x00007ffff788f72f in sys_write (l=<optimized out>, uap=0x7ffffffed5f0, retval=0x7ffffffed5e0) at /home/tazaki/gitwo
buildrump.sh/src/lib/librump/../../sys/rump/../kern/sys_generic.c:323
#6 0x00007ffff78de3cd in sy_call (rval=0x7ffffffed5e0, uap=0x7ffffffed5f0, l=0x700800, sy=<optimized out>) at /home/ta
buildrump.sh/src/lib/librump/../../sys/rump/../sys/syscallvar.h:61
#7 rump_syscall (num=num@entry=4, data=data@entry=0x7ffffffed5f0, dlen=dlen@entry=24, retval=retval@entry=0x
at /home/tazaki/gitworks/buildrump.sh/src/lib/librump/../../sys/rump/librump/rumpkern/rump.c:1024
#8 0x00007ffff78d573b in rump___sysimpl_write (fd=<optimized out>, buf=<optimized out>, nbyte=<optimized out>
tazaki/gitworks/buildrump.sh/src/lib/librump/../../sys/rump/librump/rumpkern/rump_syscalls.c:121
#9 0x0000000000400d08 in main () at webbrowser.c:86
(gdb)
10

11. OSv
BSD
Stack
glue
apps
(java)
(gdb) bt
#0 if_transmit (ifp=0xffffc0003fdfa800, m=0xffffc00005bfe100) at ../../bsd/sys/net/if.c:3082
#1 0x0000000000252a57 in ether_output_frame (ifp=0xffffc0003fdfa800, m=0xffffc00005bfe100) at ../../bsd/sys/net/if_e
#2 0x0000000000252a0a in ether_output (ifp=0xffffc0003fdfa800, m=0xffffc00005bfe100, dst=0xffffc0003e9e8db0,
ro=0x2000059102a0) at ../../bsd/sys/net/if_ethersubr.c:356
#3 0x0000000000277982 in ip_output (m=0xffffc00005bfe100, opt=0x0, ro=0x2000059102a0, flags=0, imo=0x0,
inp=0xffffc00009ea6400) at ../../bsd/sys/netinet/ip_output.c:612
#4 0x000000000028cb49 in tcp_output (tp=0xffffc00009eafc00) at ../../bsd/sys/netinet/tcp_output.c:1219
#5 0x0000000000296276 in tcp_output_connect (so=0xffffc0000a5a0800, nam=0xffffc00005a8e140) at ../../bsd/sys/netin
tcp_offload.h:270
#6 0x0000000000296b25 in tcp_usr_connect (so=0xffffc0000a5a0800, nam=0xffffc00005a8e140, td=0x0) at ../../bsd/sys
tcp_usrreq.c:453
#7 0x000000000023503e in soconnect (so=0xffffc0000a5a0800, nam=0xffffc00005a8e140, td=0x0) at ../../bsd/sys/kern/u
744
#8 0x000000000023ad0e in kern_connect (fd=46, sa=0xffffc00005a8e140) at ../../bsd/sys/kern/uipc_syscalls.c:364
#9 0x00000000002511fa in linux_connect (s=46, name=0x200005910660, namelen=16) at ../../bsd/sys/compat/linux/linu
#10 0x000000000023c088 in connect (fd=46, addr=0x200005910660, len=16) at ../../bsd/sys/kern/uipc_syscalls_wrap.c:1
#11 0x000010000220c65a in NET_Connect ()
#12 0x000010000220d0fa in Java_java_net_PlainSocketImpl_socketConnect ()
#13 0x000020000021cd8e in ?? ()
#14 0x00002000059106d8 in ?? ()
(snip)
(gdb)
11

12. DCE
(dce:node0) bt
#0 sim_dev_xmit (dev=0x7ffff5587020, data=0x7ffff3e0688a "", len=105) at arch/sim/sim.c:349
#1 kernel_dev_xmit (skb=0x7ffff5ccaa68, dev=0x7ffff5587020) at arch/sim/sim-device.c:20
#2 dev_hard_start_xmit (skb=0x7ffff5ccaa68, dev=0x7ffff5587020, txq=0x7ffff5571a90) at net/core/dev.c:2580
#3 dev_queue_xmit (skb=0x7ffff5ccaa68) at net/core/dev.c:2830
#4 neigh_hh_output (skb=0x7ffff5ccaa68, hh=0x7ffff5ce8850) at include/net/neighbour.h:357
#5 dst_neigh_output (skb=0x7ffff5ccaa68, n=0x7ffff5ce8790, dst=0x7ffff3e045d0) at include/net/dst.h:409
#6 ip_finish_output2 (skb=0x7ffff5ccaa68) at net/ipv4/ip_output.c:201
#7 ip_finish_output (skb=0x7ffff5ccaa68) at net/ipv4/ip_output.c:234
#8 ip_output (skb=0x7ffff5ccaa68) at net/ipv4/ip_output.c:307
#9 dst_output (skb=0x7ffff5ccaa68) at include/net/dst.h:448
#10 ip_local_out (skb=0x7ffff5ccaa68) at net/ipv4/ip_output.c:110
#11 ip_queue_xmit (skb=0x7ffff5ccaa68, fl=0x7ffff3e04e78) at net/ipv4/ip_output.c:403
#12 tcp_transmit_skb (sk=0x7ffff3e04bd0, skb=0x7ffff5ccaa68, clone_it=1, gfp_mask=32) at net/ipv4/tcp_output.c:1021
#13 mptcp_write_xmit (meta_sk=0x7ffff3e053d0, mss_now=1428, nonagle=0, push_one=0, gfp=32) at net/mptcp/mptcp_output.c:1
#14 tcp_write_xmit (sk=0x7ffff3e053d0, mss_now=516, nonagle=0, push_one=0, gfp=32) at net/ipv4/tcp_output.c:1930
#15 __tcp_push_pending_frames (sk=0x7ffff3e053d0, cur_mss=516, nonagle=0) at net/ipv4/tcp_output.c:2154
#16 tcp_push_pending_frames (sk=0x7ffff3e053d0) at include/net/tcp.h:1610
#17 do_tcp_setsockopt (sk=0x7ffff3e053d0, level=6, optname=3, optval=0x7ffff439cc78 "", optlen=4) at net/ipv4/tcp.c:2625
#18 tcp_setsockopt (sk=0x7ffff3e053d0, level=6, optname=3, optval=0x7ffff439cc78 "", optlen=4) at net/ipv4/tcp.c:2762
#19 sock_common_setsockopt (sock=0x7ffff3e03850, level=6, optname=3, optval=0x7ffff439cc78 "", optlen=4) at net/core/sock.c:24
#20 sim_sock_setsockopt (socket=0x7ffff3e03850, level=6, optname=3, optval=0x7ffff439cc78, optlen=4) at arch/sim/sim-socket.c:16
glue(linux) #21 sim_sock_setsockopt_forwarder (v0=0x7ffff3e03850, v1=6, v2=3, v3=0x7ffff439cc78, v4=4) at arch/sim/sim.c:97
#22 ns3::LinuxSocketFdFactory::Setsockopt (this=0x64f000, socket=0x7ffff3e03850, level=6, optname=3, optval=0x7ffff439cc78, optl
linux-socket-fd-factory.cc:947
glue(POSIX)#23 ns3::LinuxSocketFd::Setsockopt (this=0x815f20, level=6, optname=3, optval=0x7ffff439cc78, optlen=4) at ../model/linux-socket-f
#24 dce_setsockopt (fd=11, level=6, optname=3, optval=0x7ffff439cc78, optlen=4) at ../model/dce-fd.cc:529
#25 setsockopt () at ../model/libc-ns3.h:179
#26 sockopt_cork (sock=11, onoff=0) at sockunion.c:534
#27 bgp_write (thread=0x7ffff439ce10) at bgp_packet.c:691
#28 thread_call (thread=0x7ffff439ce10) at thread.c:1177
#29 main (argc=5, argv=0x658100) at bgp_main.c:455
#30 ns3::DceManager::DoStartProcess (context=0x6fa970) at ../model/dce-manager.cc:281
#31 ns3::TaskManager::Trampoline (context=0x6fab50) at ../model/task-manager.cc:274
12
#32 ns3::UcontextFiberManager::Trampoline (a0=32767, a1=-139668064, a2=0, a3=7318352) at ../model/ucontext-fiber-manager.cc:1
glue
Linux
Stack
apps

13. valgrind
==5864== Memcheck, a memory error detector
==5864== Copyright (C) 2002-2009, and GNU GPL'd, by Julian Seward et al.
==5864== Using Valgrind-3.6.0.SVN and LibVEX; rerun with -h for copyright info
==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-manager.cc:261)
==5864== Uninitialised value was created by a stack allocation
==5864== at 0x7D65B30: tcp_check_req (tcp_minisocks.c:522)
==5864==
13

14. gdb
Home Agent
AP1
correspondent
node
ping6
AP2
Wi-Fi
Wi-Fi
handoff
mobile node
(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
14

15. CI
• Linuxカーネルテスト
• gcov
• nightly build/tests
15

16. ありがとうございました
Direct Code Execution
http://bit.ly/ns-3-dce
https://github.com/direct-code-execution
16