Getting started with cisco VIRL L2 virtual Ethernet switches

Well for the longest time there was no generally available way to emulate a cisco L2 switch. right before Dynamips was abandoned, in 0.28RC1, there was actually some work on the the Catalyst 6000 Supervisor 1 line card, although no interfaces are supported, and it was largely seen as impossible at the time.

While there may have been leaks of the internal IOU or IOS on UNIX, these are even more dubious than buying your own cisco 7200 and running that IOS on Dynamips.  Indeed in the old days you’d no doubt find people with home labs that look something like this:

My sad lab.

So yeah, I know it’s not new but it was new to me.  But yes, VIRL is something us mere mortals can buy without a CCIE on hand, or a multi-million dollar contract on hand.  Although it isn’t free, but compared to everything else cisco sells it’s cheap…

So VIRL comes in a few different flavors.  They do have an ISO to run on bare metal x86 machines, OVAs for deployment on VMWare Workstation, and ESXi (Although for player you’ll have to get VIX and the vmnet config util from workstation, as I went through here & here).

Although that’s not so much what I’m interested in.  As always I’m more interested in something that lets me run it on my own.

Downloading the l2 image

So as of today, the latest file is vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E, with the MD5 checksum of 1a3a21f5697cae64bb930895b986d71e.

So as a first test, you can run the L2 image with Qemu/KVM!  I found it works better renaming vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E to vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E.vmdk otherwise there was some issues with Qemu picking up the image.

The command line for a switch can be a little crazy so it’ll break some of it up onto separate lines.  This way you can see that I bound a few interfaces to listen on UDP, while most of them are unbound, but you get the idea.  Naturally it being a cisco product, it drives with a serial console.

qemu-system-i386w.exe
-m 768M
-smp cpus=1
-boot order=c
-drive file=vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E.vmdk,if=ide,index=0,media=disk
-serial telnet:127.0.0.1:5000,server,nowait
-monitor tcp:127.0.0.1:51492,server,nowait
-net none -device e1000,mac=00:2e:3c:92:26:00
-device e1000,mac=00:2e:3c:92:26:01,netdev=gns3-1
-netdev socket,id=gns3-1,udp=127.0.0.1:10003,localaddr=127.0.0.1:10002
-device e1000,mac=00:2e:3c:92:26:02
-device e1000,mac=00:2e:3c:92:26:03
-device e1000,mac=00:2e:3c:92:26:04
-device e1000,mac=00:2e:3c:92:26:05,netdev=gns3-5
-netdev socket,id=gns3-5,udp=127.0.0.1:10000,localaddr=127.0.0.1:10001
-device e1000,mac=00:2e:3c:92:26:06 -device e1000,mac=00:2e:3c:92:26:07
-device e1000,mac=00:2e:3c:92:26:08 -device e1000,mac=00:2e:3c:92:26:09
-device e1000,mac=00:2e:3c:92:26:0a -device e1000,mac=00:2e:3c:92:26:0b
-nographic

In some ways, this is very much like running Solaris on QEMU via a serial console.  Once booted up, if you grab the console you’ll see:

l2’s grub console

Now, while I think it’s interesting to play with, but I know many people don’t like to setup and run a dozen programs manually, so how do we get this to run under GNS3!

As of right now the current version is 1.5.3, so let’s step through this real quick

Version 1.5.3

First when you fire it up (by default) you’ll get the option to specify using a local server

use local server

Next you will want to check the box to add a Qemu VM

Add a Qemu VM

give it a name like adventerprisek9-m.vmdk.SSA.152-4.0.55.E… Or anything else you wish to call it.

give it a name

Next I set the emulator to qemu-system-i386.exe and give it 768MB of RAM.

set the Qemu emulator & RAM

hit next, and then it’ll prompt to select a disk image.  In this example, remember I had renamed the downloaded VIRL image to have a VMDK extension.

select the image

Then GNS3 will prompt to add it to the default images directory

add it to the images directory

After that the wizard is complete.

Then finish

However there is still a bunch of settings that still need to change.  If you don’t make these changes you’ll have a switch with a single Ethernet port, and you will only be able to deploy a single switch, so that won’t be any fun!.

Once the wizard has finished you’ll be in the Preferences.  Just hit edit, on the template we just added, or otherwise it’s under Edit->Preferences.

Hit edit

First thing is kind of cosmetic, but go ahead and set the Category to Switches, so that way it ‘flows’ nice in the UI.

set category

Next hit the Network tab, and then add some adapters.

set the adapters to something more usable like 12

I’ve set the switch to 12 adapters.  The default of 1 isn’t too useful.  Next up hit the Advanced settings tab.  Be sure to un-check the ‘Use as a linked base VM’ . This will let you deploy multiple copies.  On Windows there is some weird issue where changes are seemingly not saved, so be sure to have a config backup strategy beyond saving the config locally.

uncheck the Use as linked base VM

Great, hit OK, and now we’ve got our L2 template for GNS3!

As a bonus, I put it on Linux, and it’ll run under KVM, however if you use the cisco downloaded files, you’ll see this error while booting:

-Traceback= 1DBB7C8z 8DBFE5z 90522Ez 904F50z 904D5Dz 900F45z 901B7Bz 901B0Fz 8D7C0Dz 8D7B0Dz 887061z 8BAE73z 8B9FD7z 8B7827z 8BCCC4z 8C0587z – Process “Async write process”, CPU hog, PC 0x008D7D62

Over and over, and it’ll be generally slow.  For some reason KVM/Qemu on Linux is struggling with the VMDK.  So the solution is to simply convert it from a VMWare VMDK into a Qcow2 image with:

qemu-img convert -f vmdk -O qcow2 vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E.vmdk  vios_l2-adventerprisek9-m.vmdk.SSA.152-4.0.55.E.qcow2

Now using the qcow2 file, the switch will boot up just fine!

For any reference I’m running Ubuntu 16.10

and the KVM version is:

# kvm –version

QEMU emulator version 2.6.1 (Debian 1:2.6.1+dfsg-0ubuntu5.3), Copyright (c) 2003-2008 Fabrice Bellard

Nested VMWare ESXi

Virtual datacenter

My physical ESXi box, a lowly AMD FX 8320

One of the more cooler features of VMWare 5 is that it is capable of running itself.  While it

may seem silly at first, this is a great way to build a virtual environment where you can test scripts for provisioning (and destroying) stuff, along with testing API level calls without having to worry about screwing up production, begging for a ‘lab’ environment, or even better snapshotting the whole thing so you can revert whatever it is you are doing at a block level.  In short virtual datacenters really rock, especially for people like me who like to play in a really destructive manner.

So the first thing is that for this test I’m going to use a ‘freebie’ ESXi that I’ve been using for quite some time.  Naturally this should work for version 6, but since the stuff that I’m testing is all in 5.0 and 5.5 (the majority being 5.5) I wan to build a 5.5 environment.  In my insane scenario I have deployment access to a 2003 R2 x64 server with .net 2.0, and the majority of the environment I care about is VMWare ESX 5.5 along with vCenter. 5.5 on Windows 2008 servers.  So trying to mirror this a bit, that means that I’m going to skip the new fangled appliance, I don’t know if it really matters for what I want, but for the sake of trying to keep things the same I’m going to match what I can.

Creating the VMWare ESXi VM

I setup a generic ‘Other 2.6.x Linux (64-bit)’ VM, with a single socket, dual core processor, 4GB of RAM, a LSI SAS controller, with a 32GB disk, and 3 NIC’s with the VMXNET3 driver.  For some reason I had to change the CPU to explicitly allow for hardware MMU emulation.

Hardware MMU emulation

It’s also worth mentioning that when you are going to run ESXi on ESXi that any physical adapters that you want your virtual ESXi host to be able to lauch VMs and have them communicate onto you will need to enable the ‘Forged Transmits’ setting in the vSwitch properties.

vSwitch properties

With that in place, I was able to use my ESXi 5.5 ISO, and install into the VM.  There isn’t much to really say the installer will install ESXi, and reboot and you get the console.

ESXi running on ESXi

I went ahead and gave this ESXi server a static address, and that was pretty much it for the server.

Installing vCenter

I went ahead and used an eval copy of 2008 R2 that is available at Microsoft here.  The installation is really simple, not much to say but for my needs I gave the VM a static address, HOWEVER I did NOT install Active Directory as you cannot install vCenter onto a DC, and I really was not in the mood to have a DC along with a vCenter 2008 VMs as I’m only interested in doing API testing I don’t care about authentication plugins I’m only concerned with other aspects.  Obviously if you do care, then you’ll want to install 2 2008 servers.  I gave my 2008 server a static address of 192.168.1.12 so that I could easily find it on the network post-install.

Since I have no imagination, I renamed the server “vcenter” which of course will factor into the login credentials later on.

My ‘client’ gave me the ISO for vCenter “VMware-VIMSetup-all-5.5.0-3254792-20151201-update03.iso” which of course needs to be installed onto the 2008 server.

install vSphere vCenter

I did the easy install, as again I’m not building a real enterprise.  However I should point out that the easy install has a habit of popping alerts and prompts UNDER the current window so you could be waiting for quite a long long time for this to install when it really shouldn’t take all that long.  I also kept the option for the 2008 Express edition as I’m not going to try to stress the count of VMs 50 is far more than I require as again I’m only interested in limited stuff at this point.

vCenter ‘simple install’ ports

Again I just selected the defaults for the install as I’m not all that worried.  Phew with all of that done, it’s now ready to use!

Logging in

Now I went ahead and hit the following site:

https://192.168.1.12:9443/vsphere-client/#

I went ahead and installed the pluggin for a more ‘full’ experience with the web client.  The link is on the bottom of the page.

download this!

With all of that in place, I finally could use the web/flash site to login, using the local administrator account.  However upon logging in the domain was barren, no vcenters no data centers, nothing.

Empty data-center!

Obviously I must have screwed something up!  Even worse using the ‘fat’ C#/J# client (that I still love…) I would simply get this fun error:

You do not have permission to login to the server!

What? I don’t have permission?

A little digging around, and I found out of course, that it is because I don’t have an Active Directory, and that for ‘workgroup’ installs like this, you need to simply login as administrator@machine.local or ‘administrator@vsphere.local’ in my case, using the password that had to be set during the SSO installation.

Login

And now I was prompted to create my data-center, and add in the ESXi server into the virtual data-center.

vCenter is now operational

So now I have a virtual vCenter, along with an ESXi host to deploy stuff onto, and destroy all I want.  Even better VMWare Player & VMWare Fusion can also run ESXi nested, so you can take your virtual data-center with you on a laptop!  You can boot 2008 with vCenter in 2GB of RAM, although it really should have 4GB if not more, and with 4GB for an ESXi server that would be 8GB+ on any laptop or desktop.  However I’m lucky my ESXi server has 32GB of RAM, and my laptop has 16.  So it’s also a great excuse to upgrade!

IPIP tunnel to SLiRP

I know this is what 99.99% of people hope I never do, but let’s make an incredibly insecure VPN! yay!

Motivation

So the thing is that I have a cisco router and I’d love for it to connect to some Windows machine over an existing OpenVPN, and NAT out the Windows side.  Except for getting the VPN installed, they won’t give me anything else.  And they SURE as heck won’t let me connect a cisco router up…..

So first things first, I need to configure my cisco router for an IPIP tunnel, to my test Windows machine, and use the SLiRP default addresses:

interface Tunnel0
description “SLiRP tunnel”
ip address 10.0.2.15 255.255.255.0
ip mtu 1452
tunnel source GigabitEthernet0/1
tunnel destination 192.168.1.10
tunnel mode ipip
end

Now to start programming.

Well then I went looking and found this fun filled page, about calling winioctl’s myself, and getting winsock to do all kinds of fun things.  Namely how IPIP actually works, as it’s is it’s own protocol (none of that pesky TCP/UDP it’s IPIP!) and more importantly I can receive the traffic.

So looking at a quick UDP client/server I figured out that I can modify that so instead of listening with UDP like this:

if((s = socket(AF_INET , SOCK_DGRAM , 0 )) == INVALID_SOCKET)

I can instead call for a RAW socket, and listen on protocol #4 aka IPIP.

if((s = socket(AF_INET , SOCK_RAW , 4 )) == INVALID_SOCKET)

One caveat I had on this, is that you need to run as Administrator on the Windows machine to create raw sockets.  If you don’t have administrator privleges you’ll get this error:

Could not create socket : 10013socket() failed with error code : 10013

Now add in some nonblocking, and feed the data into SLiRP, and I got invalid data!  Using wireshark I can see that I only receive the IP portion of the data, so no hardware frame, but what is more interesting is that I receive ALL of the IP information so I get the IP+IP+DATA.  So I have to forge a L2 header, and cut out the first IP header.  I did this by cheating, using the following for a L2 header:

0x44,0x8a,0x5b,0x62,0xcb,0xaf,0x00,0x1b,0x90,0x21,0x58,0x1b,0x08,0x00

I then just memcpy that to the start of my buffer, then copy in the rest of the received data like this:

memcpy(buf2+14,buf+20,recv_len-20);

And now I can forge data going to SLiRP to make it happy!

And sending replies didn’t make wireshark happy at all, as there is an L2 header in there, that just doesn’t make sense in L3 space, so I trimmed that with the following:

memcpy(buf,qp->data+14,qp->len-14);

Putting it all together

And now much to my amazement I can ping SLiRP from my 7206!

IPIP Ping!

Ok, I know what you are thinking. ICMP is great, but how about TCP?  Can I actually use this thing?

I add a route to my BBS over the SLiRP tunnel, with a simple route statement:

ip route 172.86.181.35 255.255.255.255 10.0.2.2

and then telnet…

Telnet to my BBS over IPIP to SLiRP

So yes, it does actually work!\

I don’t think anyone will ever want to use this, but for me it’s 100% novelty in that I could.

Executable & source code is here, ipip.7z.

I suppose later I could look at ipdecap, to work out how to work with GRE.

User Mode Linux revisited (UML) aka SLiRP networking

So my uh ‘friend’ that got into trouble when he found out that his ‘dedicated’ machine turned out to be a VM which he couldn’t launch nested KVM VM’s, and instead found that User Mode Linux (UML), would allow them to run their touchy ancient Linux application in a psudo VM/Container.  Well they finally bit the bullet and decided to move to something better.

And by better, it was cheaper.  And why was it cheaper?  Because it is even a more restricted VM.

Great.

So naturally the panic call was made, because TUN/TAP networking was not permitted in this new VM.  So what to do.

Well, keeping in mind how Qemu gets around this problem, it binds in a copy of SLiRP.  And it turns out that UML can actually call SLiRP directly!  So cool we have an ‘out’.  First things first, we need SLiRP on the host machine.  I’m old, so that means I build it from source.That means I’m downloading slirp-1.0.16.tar.gz, along with the 1.0.17 patch.  I’m not sure if I need to go into how to extract source, patch, running configure and compiling.

One thing of note is that you really really really want to set the “FULL_BOLT” option either in the Makefile, or in config.h

With SLiRP built, I just copy it into /usr/local/bin .. I’m sure there is packages and stuff out there, but heh I’m old.

OK next up I make a small script to call SLiRP, in this case, I’m going to redirect port 80 directly into the VM.  And for a test port 2323 which then goes into port 23 (why not ssh? .. sigh don’t go there).

So my script looks like this:

#!/bin/sh
/usr/local/bin/slirp “redir 80 80” “redir 23 2323”

Pretty simple right?  I’m using a script as there will be more than one VM, so relying on .slirprc isn’t a solution for me.

./linux-2.6.24-rc7 ubd0=junk.ubda eth0=slirp,,/virtual/sl.sh

And away we go!

Inside the VM we can configure it with the usual SLiRP config:

ifconfig eth0 10.0.2.15 255.255.255.0
route add default gw 10.0.2.2

And now we can access the internal http server!

Add in some magic to /etc/resolv.conf such as:

nameserver 10.0.2.3

and it’ll automatically use whatever the host is configured to do.

As requested, PCem v11 with networking

via SLiRP

via SLiRP

injecting networking was no more difficult than it was in version 10.  It’s only a few changes to pc.c, if you look at the USENETWORKING define you’ll see them.  The best notes are on the forum.

I haven’t changed or improved anything it still requires manual configuration.

Downloads are available on my site as pcem_v11_networking.7z.  You’ll have to defeat the password protection, as always.  I included the source, it ought to be trivial to rebuild.

*For anyone using an old version the ‘nvr’ directory is missing, so PC-em is unable to create new non volatile ram save files, meaning you always loose your BIOS settings.  Sorry I missed that one.

Building a private mesh network

Well it was bound to happen sooner or later, but working on projects at the office I have segmented networks for various things, and the stuff I host only has to talk to one specific thing out on the internet.  But things change, and flexibility is demanded as now I suddenly have half a dozen VPS’s out on the internet, that not only need to talk back to my office, but also need to talk to eachother.  And of course adding that n+1 becomes tedious, and worse when one host goes down, and you have people pointing the wrong way.  If only there was a solution…

And there is, as this ‘problem’ was solved forever ago with this magical thing called routing protocol.  Before I was doing OpenVPN with a network to network type setup, but now I want to dynamically route, and considering it’s a small network, I’m free to use any protocol, even RIP is fine, as I have about 15 networks to advertise.  In the end I went with BGP for really no real reason.  RIP/OSPF,ISIS would have worked just as well.

The first thing is that to configure OpenVPN is that I didn’t want the normal ‘shared network’ setup, nor the tun style where OpenVPN intercepts the invalid destination address.  While it does bring up links, and work for dynamic setups, I’m just bringing up static links that are point to point, and single host only.  Also BGP wants the source and destination originating address to match, so a tunnel interface that is 10.0.1.6 10.0.1.5, but expects the destination to be 10.0.1.1 isn’t going to work.  So I went with the old p2p style config.

As a template I used this site right here:

First generate a static key:

openvpn --genkey --secret static.key

Next setup the config for the ‘server’ side.  In this case, each of my VPS’es is a server since they all have registered addresses, and don’t move as often.  My office is going to move soon, and in the off even that I need to travel with my office setup it’s nice to bring it online wherever, and have it connect.  At the same time if my office is down, this is why I want the VPSes to be able to talk to eachother.

Server config:

mode p2p
port 1194 #  We listen to port 1194
dev tun # possibly tun0 Linux
proto udp # protocol UDP, TCP: proto tcp-server

ifconfig 10.5.0.1 10.5.0.2 #  Local IP <-> Remote IP

# Here adjust the path to point to the generated Key
secret /etc/openvpn/static.key

ping 10 # Sends every 10 seconds a ping to the remote site
ping-restart # 180 after 3 minutes without pings reconnecting the remote
ping-timer-rem # only after we've let another peer ping-restart

verb 3 # increase to debugging
mute 50 # uncomment to debugging

Client config:

mode p2p
remote my-openvpn-server.dyndns.com 1194 # hostname / external IP of another peer, port accordingly
proto udp # protocol UDP, TCP: proto tcp-client
dev tun #  possibly tun0 Linux

ifconfig 10.5.0.2 10.5.0.1 #  Local IP <-> Remote IP

# Here adjust the path to point to the generated Key
secret /etc/openvpn/static.key

ping 10 # Sends every 10 seconds a ping to the remote site
ping-restart # 180 after 3 minutes without pings reconnecting the remote
ping-timer-rem # only after we've let another peer ping-restart

verb 3 # increase to debugging
mute 50 # uncomment to debugging

Now with the config’s in place, remembering to save with the filenames ‘server.conf’ and ‘client.conf’ in the /etc/openvpn directory, I was ready to restart the OpenVPN service (service openvpn restart) and now I could ping!

tun1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:10.5.0.2 P-t-P:10.5.0.1 Mask:255.255.255.255

and a quick ping…

root@Office-OpenVPN:/etc/openvpn# ping 10.5.0.1
PING 10.5.2.1 (10.5.2.1) 56(84) bytes of data.
64 bytes from 10.5.0.1: icmp_req=1 ttl=64 time=1.66 ms
64 bytes from 10.5.0.1: icmp_req=2 ttl=64 time=3.39 ms

Now for the routing protocol.  I went with quagga, as it is descended from zebra, and one that I’ve used before.

Configuration is pretty straight forward.  first the daemons.conf file needs to be edited for what services you are going to run.  In this case I want zebra & bgpd.

zebra=yes
bgpd=yes
ospfd=no
ospf6d=no
ripd=no
ripngd=no
isisd=no
babeld=no

Next, the zebra.conf file.  The passwords are plaintext, I wouldn’t of course paste my real passwords:

hostname office
password zebra
enable password zebra

And next is my bgpd.conf file, for my office:

hostname office
password zebra
router bgp 8888
bgp router-id 192.168.1.49
network 192.168.1.0/24
network 10.1.0.0/24
network 10.1.1.0/24
neighbor 10.5.0.1 remote-as 555
log file /var/log/quagga/bgpd.log
!log stdout

Everything is the same on the VPS, except for it’s BGP config, which is the following:

hostname vps1
password zebra
router bgp 555
bgp router-id 10.13.0.1
network 10.13.0.0/24
neighbor 10.5.0.2 remote-as 8888
log file /var/log/quagga/bgpd.log
!log stdout

So now I’ve setup a p2p connection, and now defined the networks that I’m going to share from my office, in this case it’s 192.168.1.0/24, 10.1.0.0/24, and 10.1.1.0/24.  The VPS is going to share it’s 10.13.0.0/24 network.

Now to start up the router with a ‘service quagga restart’ and all being well I can now talk to the BGPD.

telnet localhost 2605
Trying ::1…
Trying 127.0.0.1…
Connected to localhost.
Escape character is ‘^]’.

Hello, this is Quagga (version 0.99.22.4).
Copyright 1996-2005 Kunihiro Ishiguro, et al.

User Access Verification

Password:
office>

Now to check for my bgp neigbours

office> ena
office# show bgp neighbors
BGP neighbor is 10.5.0.1, remote AS 555, local AS 8888, external link
BGP version 4, remote router ID 127.0.0.2
BGP state = Established, up for 3d21h32m
Last read 00:00:33, hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
4 Byte AS: advertised and received
Route refresh: advertised and received(old & new)
Address family IPv4 Unicast: advertised and received
Message statistics:
Inq depth is 0
Outq depth is 0
Sent Rcvd
Opens: 1 0
Notifications: 0 0
Updates: 18 1
Keepalives: 5613 5612
Route Refresh: 0 0
Capability: 0 0
Total: 5632 5613
Minimum time between advertisement runs is 30 seconds

For address family: IPv4 Unicast
Community attribute sent to this neighbor(both)
1 accepted prefixes

Connections established 1; dropped 0
Last reset never
Local host: 10.5.0.2, Local port: 179
Foreign host: 10.5.0.1, Foreign port: 35722
Nexthop: 10.5.0.2
Nexthop global: ::
Nexthop local: ::
BGP connection: non shared network
Read thread: on Write thread: off

office#

And how about the routes?

office# show ip bgp
BGP table version is 0, local router ID is 192.168.1.49
Status codes: s suppressed, d damped, h history, * valid, > best, i – internal,
r RIB-failure, S Stale, R Removed
Origin codes: i – IGP, e – EGP, ? – incomplete

Network Next Hop Metric LocPrf Weight Path
*> 10.1.0.0/24 0.0.0.0 0 32768 i
*> 10.1.1.0/24 0.0.0.0 0 32768 i
*> 10.13.0.0/24 10.5.13.1 0 0 555 i
*> 192.168.1.0 0.0.0.0 0 32768 i

Total number of prefixes 4

Well isn’t that great!  For each additional connection on my client side, I change the client port.  It doesn’t matter what number I choose as my client VPN machine isn’t exposed on the internet, only the OpenVPN servers on the VPSes.  I can also combine this with a traditional OpenVPN setup where my clients get addresses on my Office Lan, and can now access all of my VPSes at once.

All I have left to do is define the additional servers into the mesh, and add in the BGP peers.  And doing it this way two VPSes in the same data centre now have a 1ms ping, instead of traversing the internet to my office, and back up.  Plus they can stay in communication if my office, or even their internet is down, as long as the internal communications of the data centre is fine.

User Mode Linux

UML

UML

Well back in the day, before the hardware visualization craze of the 2000’s back in the dark days of 1999, there was UML, or better known as User Mode Linux.  Sadly the freshmeat announcement is all but lost, but sourceforge is still with us so we have the archives.

UML, simply put is a Linux kernel that has been modified to run in user space.  So to the OS, it is just another usermode program.  Because it runs in user space, there is no kernel dependencies, or special hardware required, as UML is just a user program.  Much in the way Qemu emulates a full machine, UML instead is the kernel process running with paravirtualized drivers so it should give overall a better/faster experience than hosting via Qemu.  Keeping in mind that VMware was a 1.0 launch product in may of 1999, and Bochs was back from 1994.

So what happened to UML?  The market was just too young to understand the power of hosted virtual machines, although there were some at the time.  Overall the market was in the idea of large servers that could ‘share’ thousands of websites, and most people didn’t either want to run root in their own little world, or didn’t even know there were other options besides getting an entire physical box.  I used to rent some UML VM out from a Canadian outfit back when I’d stream audio out on shoutcast, as I found my crappy connection at home couldn’t handle more than 5 listeners, but I could stream to the UML instance, and have it advertise out on shoutcast, and handle the 20-30 users I’d get back then.  Now that we live in the gated walled world of corporate hosting, I don’t think most people would even imagine going through the hell of building their own hosting infrastructure.

So it’s 2016, who cares today?

Well this… ‘friend’ of a ‘friend’ bought what they thought was a dedicated machine in a one year contract.  Except it turned out to be a KVM VM, with ‘dedicated’ processors to the instance.  Ouch.  They also got a bunch of ip addresses, but the idea of being able to run their web servers in VMs, along with an OpenVPN concentrator seemed to become an impossibility.  Obviously user mode Qemu is an option but it would be far too slow.  So I figured this would be a good time to use something from the past, UML.

So the ‘base’ host is running Debian 8.1.  So the first thing to do is to install the 2 neeed packages for networking, the bridge & uml utilities.

apt-get install bridge-utils uml-utilities
apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386

And with that in place I want to run 32bit UML kernels, which means I need the 32bit ‘runtime’ so the Debian way to enable 32bit exe’s is:

dpkg –add-architecture i386
apt-get update
apt-get upgrade
apt-get install libc6:i386 libncurses5:i386 libstdc++6:i386

One thing to keep in mind about UML, or x86 Linux in general is that you cannot mix a 64bit kernel with a 32bit userland, the 64 bit kernel can run 32bit executables and libraries, but it really needs a full 64bit userland.  So from the UML page, to get going I went with the kernel linux-2.6.24-rc7.bz2 and an ancient copy of Debian 4.0 I found here.

For anyone interested in more ‘modern’ kernels and filesystems, be sure to check out uml.devloop.org.uk & fs.devloop.org.uk.

Ok, now we want to add a bridge interface for this type of setup.  The idea is that the UML’s will have ONLY an internal connection to the bridge, as the base machine owns all the physical addresses.

So it being Debian we modify the /etc/network/interfaces file to add:

auto br0
iface br0 inet static
address 10.13.0.1
netmask 255.255.255.0
network 10.13.0.0
broadcast 10.13.0.255
bridge_fd 9
bridge_hello 2
bridge_maxage 12
bridge_stp off
pre-up brctl addbr br0
post-down brctl delbr br0

The choice of 10.13.0.0/24 is 100% up to you.  You can use any RFC 1918 address without any issues.  Now I put this stuff in a script to fire up a UML host that will create my tap0 interface, bring it up, add it to the bridge, and fire up the UML.  On termination it’ll remove the tap from the bridge, and delete the interface.

tunctl -t tap0
ifconfig tap0 0.0.0.0 promisc up
brctl addif br0 tap0
./linux-2.6.24-rc7 ubda=test_fs eth0=tuntap,tap0 mem=512M
brctl delif br0 tap0
tunctl -d tap0

And once UML has booted up, a simple ifconfig can bring up the network, and I should be able to ping the bridge address

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
(none):~# ifconfig eth0 10.13.0.10 netmask 255.255.255.0
(none):~# ping 10.13.0.1
PING 10.13.0.1 (10.13.0.1) 56(84) bytes of data.
64 bytes from 10.13.0.1: icmp_seq=1 ttl=64 time=0.043 ms
64 bytes from 10.13.0.1: icmp_seq=2 ttl=64 time=0.067 ms

You get the idea.

Because I’m running some ancient debian root filesystem, I had to set the /etc/apt/sources to include the official archive to at least install things like ssh.

deb http://archive.debian.org/debian etch main

But that is pretty much that.

Now for the real fun part, putting it on the internet!  I’ve found that this is a simple way to redirect in port 80 on the registered address I want to use, and it allows the UML instance to NAT out the same address.

/sbin/iptables -t nat -A POSTROUTING -s 10.13.0.10/32 -o eth0 -j SNAT –to 1.2.3.4
/sbin/iptables -t nat -A PREROUTING -i eth0 -p tcp –dport 80 -d 1.2.3.4 -j DNAT –to 10.13.0.10:80
/sbin/iptables -t nat -A POSTROUTING -s 10.13.0.10/32 -o eth0:0 -j MASQUERADE

Remember that you’ll also need to enable ipv4 forwarding for this to work!  You’ll need to run:

sysctl -w net.ipv4.ip_forward=1

or add it to /etc/rc.local
And with all that done, the 32bit web server is now talking. It’s not what everyone was hoping for, but at least it’s a solution.

As an update, for those who don’t have the option of TUN/TAP bridging, there is always SLiRP, as covered here.

The client needs to access the internet!

But let’s not give them access to everything.

This is a common scenario I see, where someone needs to get updates to some magical software package on the internet.  Great.  And people just give them access to ANY site, which ends up being not only the internet (the intended destination) but the rest of their internal network.  Granted a good defense in the SDN world is inbound rules as well for each VM, but everything is never 100%.

RFC1918 defines our friends, the private address ranges:

     10.0.0.0        -   10.255.255.255  (10/8 prefix)
     172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
     192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

However the solution to this fun filled problem is to grant them HTTP/HTTPS access to the inverse of this.  Enter the netmask command.  You can give it a range, and it’ll lay out what networks to you need to add like this:
     netmask -c 0.0.0.0:9.255.255.255
     0.0.0.0/5
     8.0.0.0/7

Now I can exclude everything right up until 10.0.0.0/8 !

It’s quite the handy tool, but I didn’t see any Windows version.  So a few minutes with MinGW, and dealing with it’s weird Makefile’s way of linking things, and here you go!

This way you can permit internet access, not give them inside, access and still have a global DENY actually work.

YAY.

And if anyone is interested here are the networks:

     0.0.0.0/5
     8.0.0.0/7
    11.0.0.0/8
    12.0.0.0/6
    16.0.0.0/4
    32.0.0.0/3
    64.0.0.0/2
   128.0.0.0/3
   160.0.0.0/5
   168.0.0.0/6
  172.0.0.0/12 
 172.32.0.0/11
 172.64.0.0/10
 172.128.0.0/9
   173.0.0.0/8
   174.0.0.0/7
   176.0.0.0/4
   192.0.0.0/9
192.128.0.0/11
192.160.0.0/13
192.169.0.0/16
192.170.0.0/15
192.172.0.0/14
192.176.0.0/12
192.192.0.0/10
   193.0.0.0/8
   194.0.0.0/7
   196.0.0.0/6
   200.0.0.0/5
   208.0.0.0/4

Yes, I know it’s a LOT of typing.

One million packets served!

one million ICMP packets!

Success rate is 100 percent (1000000/1000000)!

So over in my work on porting Dynamips to MinGW, I’ve created a version of SLiRP that sends and receives data over UDP.  In retrospect, something I should have done a long time ago, as it makes troubleshooting it easier as now if it were to crash it’s a stand alone program, so it won’t crash the emulator.

The good news is that I’ve been able to copy files into the virtual router using HTTP.  I’ve even been able to access my OS/2 machine over FTP and load a file!

R1#copy ftp://10.12.0.14/README disk0:
Destination filename [README]?
Accessing ftp://10.12.0.14/README…
Loading README !
[OK – 76743/4096 bytes]

76743 bytes copied in 8.740 secs (8781 bytes/sec)

R1#dir disk0:README
Directory of disk0:/README

12 -rw- 76743 Sep 18 2015 09:01:08 +00:00 README

66875392 bytes total (41652224 bytes free)

Which is very cool!

Part of the ‘trick’ is that you should set your time out to be as long as possible to send a million packets.  I just set the maximum values.

line con 0

exec-timeout 35791 23
stopbits 1

line aux 0

stopbits 1

line vty 0 4

exec-timeout 35791 0
timeout login response 300
password cisco
login

!
end

In addition, a 7200 with idle performs MUCH better than a 1700 without idle.  There is something up with ptask, and only dispatching packets every so often.  I’m guessing it’s done that way for a reason.

Also one other cool IOS trick I learned today is that you can redirect to a file resource! Say you want that ‘show tech-support’ as a file on the disk? No problem!

show tech-support | redirect disk0:tech.txt

And of course the newer versions of IOS have a ‘do’ command that you can run from config mode to execute user commands.

R1(config)#do who
Line User Host(s) Idle Location
* 0 con 0 idle 00:00:00
2 vty 0 idle 15:24:11 10.0.2.2
3 vty 1 idle 14:59:56 10.0.2.2
4 vty 2 idle 13:43:44 10.0.2.2
5 vty 3 idle 11:23:44 10.0.2.2

 Take that Junos!

For anyone interested, the binary is included in the latest binary snapshot, and using it is pretty simple:

slirp_rdr.exe 20001 127.0.0.1 20000

This will listen on port 20001, and send traffic to 127.0.0.1 on port 20000.  Easy right?

Manually interfacing from the hypervisor can be the ‘fun’ part.  I haven’t tested with any of the tools, as I don’t know if they will let you leave something ‘listening’ that isn’t connected. For my tests I end up building something with their UI, then loading up my hypervisor that logs, and seeing what it is actually doing so I can inject stuff like this:

nio create_udp nio_udp99 20000 127.0.0.1 20001
ethsw add_nio S1 nio_udp99
ethsw set_access_port S1 nio_udp99 1

This creates a udp nio, and attaches it onto the virtual etherswitch S1, and puts it on VLAN 1.  As you can see it listens on UDP port 20000, which is where slirp_rdr is setup to send it’s data to, and it’ll send to 20001 where slirp_rdr is listening.

I’ve hard coded port 42323 to telnet into 10.0.2.15.  As always SLiRP is hard coded to have the following ip address schema:

Gateway 10.0.2.2
DNS 10.0.2.3
Netmask 255.255.255.0

Be sure to set your router to 10.0.2.15/24 for this to work, and add 10.0.2.2 as your default gateway.

The ONLY address that will respond to ping is 10.0.2.2 .  This is just the way SLiRP is.  HTTP and TCP based stuff works best, things like PPTP will not.  It’s really hit and miss, but the cool thing is that it doesn’t require any device drivers, it’s all user mode code!