I'd like to learn and play with tcp/ip libraries for python, java or c++. But I only have one computer. Is it possible to "fake" remote computers to emulate remote hosts, under NAT end everything?
The simplest way is to run both the server and client on the same computer and use the "loopback" IP address: 127.0.0.1 which always connects to the local host. I've done this many times during testing. For example, run a local webserver on port NNN and then in the browser enter http://127.0.0.1:NNN/ In fact, 127.X.Y.Z should always talk to the local machine.
If you are using linux, you can configure dummy interfaces, then bind your client / server to different dummy interfaces.
[mpenning#Bucksnort ~]$ sudo modprobe dummy
[mpenning#Bucksnort ~]$ sudo ip addr add 192.168.12.12/24 dev dummy0
[mpenning#Bucksnort ~]$ ip addr show dummy0
6: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN
link/ether b6:6c:65:01:fc:ff brd ff:ff:ff:ff:ff:ff
inet 192.168.12.12/24 scope global dummy0
[mpenning#Bucksnort ~]$ ping 192.168.12.12
PING 192.168.12.12 (192.168.12.12) 56(84) bytes of data.
64 bytes from 192.168.12.12: icmp_seq=1 ttl=64 time=0.085 ms
^C
--- 192.168.12.12 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.085/0.085/0.085/0.000 ms
[mpenning#Bucksnort ~]$ sudo modprobe dummy -o dummy1
[mpenning#Bucksnort ~]$ sudo rmmod dummy
[mpenning#Bucksnort ~]$ ip addr show dummy0
Device "dummy0" does not exist.
[mpenning#Bucksnort ~]$
You should be able to run ipchains on these interfaces just like any other.
You can start out with talking between programs on your own computer.
You can use virtual machine software such as VirtualBox, VMWare, VirtualPC, etc to create what is essentially a second machine within yours and talk to that (though the network topology may be very slightly unusual - something more to learn about)
If you want to talk to something remote, you can rent a small cloud server running linux or windows from the likes of Amazon for pennies an hour and install whatever you want on it.
Use virtual box to install OS in your system. for any networking application, this is best. You dont have to work on two different system and its easy to see whats happening at both ends
Run to server to listen on your network adapter, or localhost. Then issue requests to that same IP and Port. Logically, it will all take place within the network driver(s), but it will still behave the same way if that IP address were addressed to another machine (barring Firewall configurations, etc)
Related
Already tried:
Connect the BBB with USB to iMac
Share internet with the board from System Preferences->Sharing
ssh to the board and then try to udhcp -i usb0
This is what it says:
udhcpc (v1.20.2) started
Gets stuck and I get and error: Write failed: Broken pipe
ssh exits
Any clues?
After some try-and-erroring, here's what worked for me:
1. Watch this video: http://www.youtube.com/watch?v=Cf9hnscbSK8
2. If your BBB was shipped after November 2013, instead of screen /dev/tty.usb*B 115200 use screen /dev/tty.usb* 115200 and actually you need to go to the /dev directory and check which of the tty.usbXXX is available for your BBB and screen it. In my case it was tty.usb131 for example
3. You continue the steps just like in the video until opkg update which would be the thing you need to do over the internet
And that it's all about it.
Your SSH session is getting stuck because you're connected to usb0 and the udhcpc command changed the IP address for it! At this point there's nothing listening on the other end of your ssh session, so your local computer's ssh client eventually fails with the broken pipe error and exits.
An obvious workaround is to connect via tty.usbserial instead of ssh to the IP address. You'd think the usb port's assigned IP shouldn't be changing though. Read on to understand what's happening.
Most people using a BBB for the first time attach them directly to their Internet connected computer using the supplied USB cable. It's exactly what the BBBs designers intended for you to do, and they've done a fantastic job with the BBBs startup web page.
That host computer shares it connection differently though depending on whether it's Windows, OS X or Linux, and how you do it varies depending on the version of the OS you're running.
Derek Molloy (Exploring BeagleBone) and Jason Kridner (Youtube OS X Beaglebone video) provide some fairly detailed instructions to use host based Internet sharing with your BBB. The Linux and Windows instructions are still good, but they need to update the OS X info for Yosemite - Apple switched their NAT and firewall software to pf from ipfw and natd. If you try running udhcpc like Jason did in his vid it doesn't work the same way as his did.
So back to your BBB SSH problem with OS X Yosemite. Here's how to see what's going on: Connect to the BBB using a serial/FTDI cable, then check the ip config of usb0 for the beaglebone.
beaglebone:~# ifconfig -a usb0
usb0 Link encap:Ethernet HWaddr 0e:be:ff:00:ff:00 inet addr:192.168.7.2
Bcast:192.168.7.3 Mask:255.255.255.252
confirm you can ping the host that's sharing it's Internet connection
beaglebone:~# ping 192.168.7.1
PING 192.168.7.1 (192.168.7.1) 56(84) bytes of data.
64 bytes from 192.168.7.1: icmp_req=1 ttl=64 time=0.681 ms
64 bytes from 192.168.7.1: icmp_req=2 ttl=64 time=0.533 ms
^C
try reaching an Internet IP (google dns)
beaglebone:~# ping 8.8.8.8
connect: Network is unreachable
check routes and confirm there's no default route out, which is why the ping above failed (a USB connected BBB has a 192.168.7.0/30 network setup by default, so it can only reach 192.168.7.0, .1, .2 and .3 addresses).
beaglebone:~# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.7.0 0.0.0.0 255.255.255.252 U 0 0 0 usb0
so if you run udhcpc it will add the missing route for you. you could also just add the route directly, but you need to setup dns as well, and with OS X Internet sharing it won't work without also changing the BBB's IP address - see links at end of this post)
beaglebone:~# udhcpc -i usb0
udhcpc (v1.20.2) started
Sending discover...
Sending discover...
and here is where udhcpc changes the IP instead of just re-using 192.168.7.2. The new IP is compatible with the IP range used by OS X Internet Sharing, so that may be why the DHCP server is returning it.
Sending select for 192.168.2.34...
Lease of 192.168.2.34 obtained, lease time 85536
udhcpc then throws an error because there's no default route to delete
/etc/udhcpc/default.script: Resetting default routes
SIOCDELRT: No such process
udhcpc then adds the default route - note carefully it's an OS X Internet Sharing 192.168.2 address, not the original 192.168.7.
/etc/udhcpc/default.script: Adding DNS 192.168.2.1
everything worked, so you can see the new route and successfully ping an external IP now
beaglebone:~# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 usb0
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 usb0
beaglebone:~# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=53 time=4.08 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=53 time=3.59 ms
^C
There are a couple of blog posts that show how to set this up permanently:
Sharing OS X Internet Connection over USB to BeagleBone Black
and
Changing usb0 IP address on the BeagleBone Black
I am facing issue with accessing Open stack VM's on LAN.
I have setup single machine(192.168.2.15) opensatck using devstack, so
all VM's are running inside this machine
My machine(192.168.2.15) has one network card(eth0) and
I have nova networking, have not installed neutron.
I have assigned static IP on eth0 of all the LAN machine( such as 192.168.2.15 and 192.168.2.16) in /etc/network/interfaces file.
System information of the Openstack Machine is as below:
Memory usage: 19% IP address for virbr0: 192.168.122.1
Swap usage: 0% IP address for br100: 10.0.0.1
Below works fine
I can access internet from VM1(10.0.0.2 which is auto assigned IP).
I can ping LAN machine(192.168.2.16) from VM1.
Openstack machine(192.168.2.15) can ping VM1(10.0.0.2).
VM1(10.0.0.2) can ping VM2(10.0.0.3).
But LAN machine 192.168.2.16 is not able to ping VM1(10.0.0.2)
So please suggest how can it be achieved ? And Please consider me as very new to Openstack and networking.
Thanks !!!
You need to assign a floating IP to the VMs you create if you want a host from outside the openstack network to connect to it. The internal IPs are only accessible from inside the openstack network.
See how to assign a floating IP to a VM here: http://docs.openstack.org/user-guide/content/floating_ip_allocate.html
To access the VM's floating IP from another host (that is not the devstack host) you should make sure that the devstack host is configured to forward packets. You can do this with:
sudo bash
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
See more details here:
http://barakme.tumblr.com/post/70895539608/openstack-in-a-box-setting-up-devstack-havana-on-your
Adding a route to client machine to openstack VM, helped me.
I am planning on using KVM in order to virtualize some GNU/Linux and Windows machines at home.
My physical network is 1gbe using Link Aggregation at some stages. In the worst case, it's still 1gbe though.
I am wondering if it is possible to "emulate" 10gbe ethernet (or anything faster than 1gbe) between two virtual machines on the same host (or one VM and the host itself) by avoiding the physical network altogether. I think for this to work they'll need to be in the same network, connected to the same virtual switch and VLAN.
Yes.
Create a bridge using brctl tool on the host:
brctl addbr vm-bridge
ifconfig vm-bridge up
For each VM specify virtio-net NIC and add them to the bridge.
Create qemu-ifup script:
#!/bin/sh
switch=vm-bridge
/sbin/ifconfig $1 promisc 0.0.0.0
/usr/sbin/brctl addif ${switch} $1
Specify this script in "-netdev" parameter of QEMU:
-netdev tap,id=net1,vhost=on,script=/home/user/qemu-ifup,ifname=vm_net1
I am using Oracle VirtualBox on Windows. I've setup NAT and forwarded ports.
When some forwarded ports are accidentally conflicting with host machine's ones, no errors are shown and all forwarded ports are failing.
Is there any possibility to detect those conflicting ports? I have used VBoxManage tool and there are neither output messages, nor verbose mode for startvm command.
Thanks
I would recommend using a combination of netstat and VBoxManage and parse the output. You can easily replace the findstr command with grep on non-Windows hosts.
First, I would get a listing of NAT ports on the VM in question. The VBoxManage showvminfo command will output a bunch of info about the configuration which you can filter to look for just the NAT rules. You will want to look for the host port and protocol fields in the output (and possibly host ip if configured) as that is what you will be looking to see if it is already in use.
C:\>vboxmanage showvminfo Linux | findstr Rule
NIC 1 Rule(0): protocol=tcp, host ip=, host port=2222, guest ip=, guest port=22
Second, using the info from above I know I need to check if anything is listening on port TCP port 2222, so I can use the netstat command to show me all the listening sockets, filtered by my criteria:
C:\>netstat -an | findstr LISTENING | findstr TCP | findstr 2222
Proto Local Address Foreign Address State
TCP 0.0.0.0:2222 0.0.0.0:0 LISTENING
Because my guest is already running I can see that it has already grabbed a connection on TCP 2222. If you don't get any output then nothing is listening on that specific port and you are safe to start your VM.
I have 2 servers(serv1,serv2) that communicate and i'm trying to sniff packets matching certain criteria that gets transferred from serv1 to serv2. Tshark is installed on my Desktop(desk1). I have written the following script:
while true; do
tshark -a duration:10 -i eth0 -R "(sip.CSeq.method == "OPTIONS") && (sip.Status-Code) && ip.src eq serv1" -Tfields -e sip.response-time > response.time.`date +%F-%T`
done
This script seems to run fine when run on serv1(since serv1 is sending packets to serv2). However, when i try to run this on desk1, it cant capture any packets. They all are on the same LAN. What am i missing?
Assuming that either serv1 or serv2 are on the same physical ethernet switch as desk1, you can sniff transit traffic between serv1 and serv2 by using a feature called SPAN (Switch Port Analyzer).
Assume your server is on FastEtheret4/2 and your desktop is on FastEthernet4/3 of the Cisco Switch... you should telnet or ssh into the switch and enter these commands...
4507R#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
4507R(config)#monitor session 1 source interface fastethernet 4/2
!--- This configures interface Fast Ethernet 4/2 as source port.
4507R(config)#monitor session 1 destination interface fastethernet 4/3
!--- The configures interface Fast Ethernet 0/3 as destination port.
4507R#show monitor session 1
Session 1
---------
Type : Local Session
Source Ports :
Both : Fa4/2
Destination Ports : Fa4/3
4507R#
This feature is not limited to Cisco devices... Juniper / HP / Extreme and other Enterprise ethernet switch vendors also support it.
How about using the misnamed tcpdump which will capture all traffic from the wire. What I suggest doing is just capturing packets on the interface. Do not filter at the capture level. After you can filter the pcap file. Something like this
tcpdump -w myfile.pcap -n -nn -i eth0
If your LAN is a switched network (most are) or your desktop NIC doesn't support promiscuous mode, then you won't be able to see any of the packets. Verify both of those things.