GreyBox is a single-host Internet simulator for offline exercise and training networks. It allows a single host (physical or VM) to provide the illusion of connectivity to the real Internet: a realistic BGP backbone topology with point-to-point link delays based on physical distance between the routers' real-world locations, combined with TopGen's application services (HTTP, DNS, email, etc.).
GreyBox depends on the following software packages:
TopGen
CORE (see https://github.com/coreemu/core)
FRR (previously Quagga)
keepalived
dhcp (server)
Running the './install.sh' script will copy all components of GreyBox to the appropriate locations on the filesystem. Also, see './contrib/greybox.spec' for instructions on how to build a GreyBox RPM package.
An example of pre-installed GreyBox and TopGen on a Fedora 38 VM can be downloaded from:
GreyBox relies heavily on TopGen (an application service simulator), and on the CORE container-based network simulator. In essence GreyBox provides an elaborate network topology configuration to be simulated by CORE, with application services to be provide by TopGen. You are encouraged to read the documentation for both TopGen (included with the package), and for CORE (at http://downloads.pf.itd.nrl.navy.mil/docs/core/core-html/).
An LXC container is wrapped around each of several instances of FRR's bgpd, to allow running them side by side as processes on the same host, rather than requiring a dedicated VM, complete with its own running guest kernel, to be wrapped around each individual bgpd instance.
In addition to providing each containerized bgpd instance with its own dedicated set of (virtual) network interfaces, the CORE simulator provides a convenient GUI for visualizing the network topology, facilitates editing the properties of each container and of the inter-container network links (implemented as virtual bridges connecting together the virtual interfaces assigned to several containers), and allows users to start command shells from inside each container for further configuration and troubleshooting.
While currently popular container orchestration solutions (e.g., Docker) are mainly targeted at running pre-packaged software bundles in containers while minimizing the expectations and dependencies required of the hosting server, CORE is designed to launch multiple instances of native software already present on the host, and is perfectly suited for GreyBox's frugal, minimalist use case.
Network interfaces belonging to the host may be bridged together with containers' virtual interfaces in a CORE topology map, thus providing simulated Internet access to external machines.
TopGen application services are hosted in a dedicated container, which is linked to every containerized BGP router over a virtual 0-delay Ethernet bridge, a.k.a. the "FTL" LAN.
As explained in the TopGen's documentation, the TopGen container will respond to any of a very large set of /32 host IP addresses, all of which are configured as secondaries on its loopback interface.
Each BGP router announces a set of static routes to its neighbors, with the next-hop value set to TopGen's FTL network address. Each router will announce a default route, but also a set of more specific /8 routes, the union of which covers all service IPs held by TopGen. The /8 routes announced by each BGP router have been carefully selected to approximately match their geographic assignment on the real-world Internet.
The result is that client-originated traffic will travel through a geographically realistic set of hops before being handed over to TopGen (via the FTL LAN) by one of the BGP routers announcing the matching /8.
While it is the designated next-hop for all routes announced into BGP by every backbone router, TopGen itself does not run any routing software, and no BGP peerings are set up over the FTL virtual LAN. When a TopGen service responds to a client request, reply packets are sourced from the same secondary loopback IP the client traffic was sent to in the first place. All such traffic is forwarded to a virtual default gateway IP address on the FTL network, redundantly supported (through VRRP) by all BGP routers on their FTL network interfaces. In practice, it doesn't matter how reply traffic from application services is routed back to the client, since the latter can't even tell, as traceroutes from the client reflect only hops on the outbound path.
After installing the GreyBox package and its dependencies, follow this basic process to set up an "Internet-in-a-box" GreyBox server:
See the documentation included with the TopGen package for recursively scraping a collection of web sites, setting up virtual email domains, and configuring multiple root, top-level, and caching name servers. Do not enable or start any TopGen services: TopGen will be brought up by the CORE network simulator as a container, using a different set of startup scripts.
NOTE: To allow TopGen's DNS service to resolve point-to-point BGP router interfaces, the IP address to FQDN hostname mappings must be loaded into the DNS database, using the following command:
topgen-mkdns.sh -f -x /usr/share/greybox/etc/backbone.hosts
It is recommended that name servers in '/etc/resolv.conf' be set to 8.8.8.8 and/or 8.8.4.4. CORE containers retain access to most of the host filesystem (except for explicitly assigned, dedicated subdirectories, e.g. '/var/log/'), and will thus refer to the TopGen-provided 8.8.8.8 and 8.8.4.4 addresses for in-game DNS resolution. If the GreyBox host retains access to the real Internet, processes not part of the simulation will be directed to the real Google-provided caching DNS servers at the same addresses, by the same '/etc/resolv.conf' file.
The GreyBox package ships with two Internet simulation maps (in the '/usr/share/greybox/maps/' folder):
backbone.imn: an entirely self-contained Internet simulation, with
69 BGP backbone router containers, a TopGen service
container, and two "client laptop" containers for
running tests (e.g. traceroute, dns resolution, text
mode email with mailx or mutt, etc.).
backbone_ext.imn: same as above, except with one of the "client"
containers replaced with an RJ-45 "ethernet"
port, which may be mapped to one of the GreyBox
host's network interfaces, which allows the
Internet simulation to be accessed over the
network from outside the GreyBox machine itself.
*NOTE:* This file must be edited before use, to
replace "ethX" with the name of one of the real
network interfaces available on the GreyBox host.
First, ensure that the CORE daemon service is running:
systemctl start core-daemon
Then, from a terminal window, load a simulation map into the CORE GUI:
core-gui /usr/share/greybox/maps/backbone.imn
When the GUI is up, press the green "play" button to start the simulation. Once the simulation is fully underway, right-click on any of the container icons to select "Shell Window -> bash" to get a terminal window from the inside perspective of that specific container. On containers representing BGP routers, one may select "Shell Window -> vtysh" for direct access to the Cisco-like user interface exposed by the FRR shell.
The GreyBox package also ships with a systemd service which, when enabled:
systemctl enable greybox
will load and start a simulation map when the GreyBox host machine boots. The default map, '/etc/greybox/map.imn', ships as an identical clone of the self-contained '/usr/share/greybox/maps/backbone.imn', and, as such, can be used immediately without modification. However, if external access to the simulation is required, one must edit '/etc/greybox/map.imn' using e.g., '/usr/share/greybox/maps/backbone_ext.imn' as a starting point.
Recent Linux installs tend to use unpredictable naming conventions for the host's network interfaces, from the traditional 'eth0' to names like 'ens32' or 'enp11s0'. Before using a network map file designed for outside connectivity (e.g., '/usr/share/greybox/maps/backbone_ext.imn'), be sure to replace the placeholder string "ethX" with the name of the real host interface you wish to dedicate to the simulation.
Additionally, ensure that interfaces dedicated to the simulation are not managed by any host networking sybsystem (e.g., NetworkManager on RedHat flavored distributions). In the simplest case, if all host interfaces are assigned to the simulation, NetworkManager may be turned off entirely:
systemctl stop NetworkManager
systemctl disable NetworkManager
Alternatively, any interface dedicated to the simulation can be marked as off-limits to NetworkManager by adding the line "NM_CONTROLLED=no" to its '/etc/sysconfig/network-scripts/ifcfg-ethX' config file. Similar steps exist (and should be followed) on distributions which are not following RedHat/Fedora conventions.
For ***best effort*** help, post your question in the `#greybox` (freenode) IRC channel.