This is a proof-of-concept smart contract program running on Unikraft. It uses command line arguments, TCP networking and 9pfs filesystem mounting to configure the behavior of the smart contract. It exposes a basic cryptographic hash functionality provided by libsodium.

Apart from the current repository, you also need to clone:

• Unikraft
• lwip
• newlib
• libsodium

Make sure each repository is on the staging branch.

It is easiest to use a file hierarchy such as:

.
|-- apps/
|   `-- app-smart-contract-config/
|-- libs/
|   |-- lwip/
|   |-- libsodium/
|   `-- newlib/
`-- unikraft/

If you use a file hierarhy different than the one above, then edit the Makefile file and update the variables to point to the correct location:

• Update the UK_ROOT variable to point to the location of the Unikraft clone.
• Update the UK_LIBS variable to point to the folder storing the library clones.

If you get a Cannot find library error at one of the following steps, you may need to add the lib- prefix to the libraries listed in the LIBS variable. For instance, $(UK_LIBS)/lwip becomes $(UK_LIBS)/lib-lwip.

Configure the build by running:

make menuconfig

The basic configuration is loaded from the Config.uk file. The basic configuration is loaded from the Config.uk file. Then add support for 9pfs, by selecting Library Configuration -> vfscore: VFS Core Interface -> vfscore: VFS Configuration. The select Automatically mount a root filesystem (/) and select 9pfs. For the Default root device option fill fs0. You should end up with an image such as the one in 9pfs_config.png. Save the conifugration and exit.

As a result of this, a .config file is created. A KVM unikernel image will be built from the configuration.

Build the unikernel KVM image by running:

make

The resulting image is in the build/ subfolder, usually named build/app-smart-contract-config_kvm-x86_64.

The resulting image is to be loaded as part of a KVM virtual machine with a software bridge allowing outside network access to the server application. Start the image by using the run script (you require sudo privileges):

$ ./run
[...]
Booting from ROM...
1: Set IPv4 address 172.44.0.2 mask 255.255.255.0 gw 172.44.0.1
en1: Added
en1: Interface is up
Powered by
o.   .o       _ _               __ _
Oo   Oo  ___ (_) | __ __  __ _ ' _) :_
oO   oO ' _ `| | |/ /  _)' _` | |_|  _)
oOo oOO| | | | |   (| | | (_) |  _) :_
 OoOoO ._, ._:_:_,\_._,  .__,_:_, \___)
                    Dione 0.6.0~6a2069e
argument is 1024
Listening on port 1024...

The 1024 is passed as a command line argument.

The server now listens for "commands". These commands are files in the mnt/ folder that will be read and processed by the smart contract program. Passing the commands add, add2, sub, sub2, hash_generic, hash_sha256, hash_sha512 will result in the program reading these files from the mnt/ folder.

On another terminal, use nc to connect via TCP to the program and send the commands:

$ nc 172.44.0.2 1024
add
22
$ nc 172.44.0.2 1024
add2
575
$ nc 172.44.0.2 1024
sub
21
$ nc 172.44.0.2 1024
sub2
17109
$ nc 172.44.0.2 1024
hash_generic
ee9710661309687d26234b42086c3d74089fb99ec2c3250243bb82562b38f818
$ nc 172.44.0.2 1024
hash_sha256
ecdac3aca55681291802ec7bf75c10d0231d1c9925ea1af74232b73231eefc7d
$ nc 172.44.0.2 1024
hash_sha512
710bd17d77dd89bc11c37f68c0bb097d4a96cb7844365b857d13263d53829297d83e634c522fe11bd19b35667162a51d8eb8c6a1cb7e4672485915964bfd7ac6

The running program will print out a summary of received commands:

Received connection from 172.44.0.1:48508
Received: add
Operation: addition
Sent: 22
Received connection from 172.44.0.1:48514
Received: add2
Operation: addition
Sent: 575
Received connection from 172.44.0.1:48516
Received: sub
Operation: subtraction
Sent: 21
Received connection from 172.44.0.1:48518
Received: sub2
Operation: subtraction
Sent: 17109
Received connection from 172.44.0.1:48532
Received: hash_generic
Operation: hash generic
Sent: ee9710661309687d26234b42086c3d74089fb99ec2c3250243bb82562b38f818
Received connection from 172.44.0.1:48534
Received: hash_sha256
Operation: hash sha256
Sent: ecdac3aca55681291802ec7bf75c10d0231d1c9925ea1af74232b73231eefc7d
Received connection from 172.44.0.1:48538
Received: hash_sha512
Operation: hash sha512
Sent: 710bd17d77dd89bc11c37f68c0bb097d4a96cb7844365b857d13263d53829297d83e634c522fe11bd19b35667162a51d8eb8c6a1cb7e4672485915964bfd7ac6

When done, close the server / KVM machine using Ctrl+c.