Mirage OS hackaton December 2017

Personal notes on MirageOS, Ocaml ecosystem and charrua-core (Ocaml DHCP client).

Thanks so much @hannesm for organizing it.

Install ocaml, opam and mirage in Debian testing/sid

Following Mirage Install:

apt install install ocaml ocaml-native-compilers camlp4-extra opam
opam init
eval `opam config env`

opam install mirage

Install charrua-core (DHCP client) local branch

git clone https://github.com/mirage/charrua-core
cd charrua-core
git checkout -b mybranch
opam pin add charrua-core .

The installed code would be now in $HOME/.opam

Use charrue-core in utop

Use charrue-core in utop (with help from @cfcs)

utop
#load "/home//user/.opam/system/lib/io-page-unix/io_page_unix.cma";;
#require "charrua-core";;
#require "charrua-core.wire";;
open Dhcp_wire;;
Dhcp_wire.ABSOLUTE_TIME;;
ABSOLUTE_TIME;;

Ocaml/Python equivalences

open Dhcp_wire;;

equivalent to:

import * from DHCP_wire

Run charrua client in unix

DHCP client (which doesn't set an IP) by @yomimono:

git clone https://github.com/yomimono/charrua-core 
git checkout unix-charruac
jbuilder build -p charrua-unix

sudo _build/default/unix/client/charruac.exe

In case it's needed to rebuild dependencies:

jbuilder clean -p charrua-client
jbuilder clean -p charrua-client-lwt
jbuilder clean -p charrua-core
jbuilder build --dev @install -p charrua-unix

sudo _build/default/unix/client/charruac.exe

To use last master version of rawlink (thanks to @yomimono and @haesbaert):

git clone https://github.com/haesbaert/rawlink
cd rawlink
opam pin add rawlink ./

Create solo5 unikernel with charrua-core

(With help from @mato)

When there's a configure.ml in the module

mirage configure -t unix
make depend
make

When there isn't. Create a tun/tap interface:

ip tuntap add tap100 mode tap
ip addr add 10.0.0.1/24 dev tap100
ip link set dev tap100 up

Then bridge to the tun/tap interface, in /etc/network/interfaces:

# Host-only bridge
iface hostbr0 inet manual
    up ip link add hostbr0-master address 02:00:00:00:00:01 type dummy
    up ip link set dev hostbr0-master up
    up ip link add hostbr0 type bridge
    up ip link set dev hostbr0-master master hostbr0
    up ip addr add 10.0.120.1/24 dev hostbr0
    up ip link set dev hostbr0 up
    post-up /usr/sbin/dnsmasq -9RhK -i hostbr0 -F 10.0.120.128,10.0.120.254 -p 0 -x /var/run/dnsmasq-hostbr0.pid
    pre-down kill $(cat /var/run/dnsmasq-hostbr0.pid)
    down ip link del hostbr0
    down ip link del hostbr0-master

With an IP

cd mirage-skeleton/device-usage/network
opam switch
opam list
mirage configure -t ukvm
make depend
make
./ukvm-bin --net=tap100 ./network.ukvm --ipv4=10.0.10.2/24 --logs=\*:debug

With DHCP

cd mirage-skeleton/device-usage/network
rm mirage-unikernel-network-ukvm.opam 
mirage configure -t ukvm --DHCP=true
make depend
make
./ukvm-bin --net=tap100 ./network.ukvm  --logs=\*:debug 

To use the local charrua-core git branch:

cd charrua-core 
opam pin add charrua-client-mirage ./

cd mirage-skeleton/device-usage/network
mirage clean
mirage configure -t ukvm --DHCP=true
make
./ukvm-bin --net=tap100 ./network.ukvm  --logs=\*:debug 

Execute an script from Ocaml

(Helped by @reynir and @yomimono) Using Bos library

Without envirnoment variables:

#require "bos";;
open Bos;;
OS.Cmd.to_null (OS.Cmd.run_io Cmd.(Cmd.v "mplayer" % "example.ogg") OS.Cmd.in_null);;

Passing envirnoment variables:

let myenv = Astring.String.Map.empty;;
let myenv = Astring.String.Map.add "reason" "foo" myenv;;
OS.Cmd.to_null (OS.Cmd.run_io ~env:myenv Cmd.(Cmd.v "/sbin/dhclient-script") OS.Cmd.in_null);;

To see the environment variables passed to the script:

let myres = OS.Cmd.to_string (OS.Cmd.run_io ~env:myenv Cmd.(Cmd.v "/usr/bin/env") OS.Cmd.in_null);;
let mystr = match myres with
  | Result.Ok anything -> anything;;
print_endline letmystr;;