network-suite

Table of Contents

• Installation
• Simple Network
• Design
• Internals
• Future Work

A shell script to emulate different network setups using network namespaces.

Installation

$ git clone https://github.com/maxmoehl/network-suite
$ cd ./network-suite
$ make install # requires sudo access

Simple Network

Creating hosts and networks is simple:

# ns host add host-a
# ns host add host-b

# ns net add subnet

Connect them with the host-connect command:

# ns host connect host-a subnet 10.0.0.1/24
# ns host connect host-b subnet 10.0.0.2/24

Now both hosts can talk to each other:

# ns host shell host-a
$ ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.223 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.168 ms
64 bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=0.204 ms
^C
--- 10.0.0.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2046ms
rtt min/avg/max/mdev = 0.168/0.198/0.223/0.022 ms

For details on the different commands refer to the help output from ns (you can also check the __help function in the script).

Design

ns is built as a wrapper around ip(8) from the iproute2 package. As such, a lot of inspiration has been taken from that command. But the interface overall is kept more simple for the sake of making the script readable and POSIX compliant. For example options have to be in a fixed order instead of the key-value style of ip.

Internals

To see what is happening behind the scenes use either -v to see every single statement or -d to only print the resulting ip commands without executing them.

Each host and each network are represented by a network namespace. To separate the two kinds they get (mostly) invisible prefixes. Networks are prefixed with nsn- and hosts with nsh-. This prevents operations from changing the wrong entity.

For every network namespace the loopback interface is brought up and for networks a bridge is created. When connecting a host to a network a veth pair is created. One end in the host (named after the connected network) and the other in the network (named after the connected host). The network side has the bridge set as its master.

Future Work

TODO.adoc