HTTP reply on Unikraft

This is a minimal example HTTP server.

To configure, build and run the application you need to have kraft installed.

To get started using this application, first configure it:

$ kraft configure -p kvm -m x86_64

Build the application:

$ kraft build

Before running the application, we need a virtual bridge to create a connection between the virtual machine and the host system. The HTTP client will run on the host and the HTTP server will run on the virtual machine. We assign address 172.44.0.1/24 to the bridge interface (pointing to the host) and we assign address 172.44.0.2/24 to the virtual machine, by passing boot arguments. The IP addresses are of our choosing, they can be changed to other values.

We run the commands below to create and assign the IP address to the bridge virbr0 (once again, our choice of name; any name works):

$ sudo brctl addbr virbr0
$ sudo ip a a  172.44.0.1/24 dev virbr0
$ sudo ip l set dev virbr0 up

We can check the proper configuration:

$ ip a s virbr0
420: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether 3a:3e:88:e6:a1:e4 brd ff:ff:ff:ff:ff:ff
    inet 172.44.0.1/24 scope global virbr0
       valid_lft forever preferred_lft forever
    inet6 fe80::383e:88ff:fee6:a1e4/64 scope link
       valid_lft forever preferred_lft forever

Now we start the virtual machine and pass it the proper arguments to assign the IP address 172.44.0.2/24:

$ kraft run -b virbr0 "netdev.ipv4_addr=172.44.0.2 netdev.ipv4_gw_addr=172.44.0.1 netdev.ipv4_subnet_mask=255.255.255.0 --"
[...]
0: Set IPv4 address 172.44.0.2 mask 255.255.255.0 gw 172.44.0.1
en0: Added
en0: Interface is up
[...]
Listening on port 8123...

The boot message confirms the assigning of the 172.44.0.2/24 IP address to the virtual machine. It's listening on port 8123 for HTTP connections on that IP address. We use wget to validate it's working properly and we are able to get the index.html file:

$ wget 172.44.0.2:8123
--2021-08-18 16:47:38--  http://172.44.0.2:8123/
Connecting to 172.44.0.2:8123... connected.
HTTP request sent, awaiting response... 200 OK
[...]
2021-08-18 16:47:38 (41.5 MB/s) - ‘index.html’ saved [160]

You can also the application manually:

$ sudo qemu-system-x86_64 \
         -netdev bridge,id=en0,br=virbr0 \
         -device virtio-net-pci,netdev=en0 \
         -kernel "build/app-httpreply_kvm-x86_64" \
         -append "netdev.ipv4_addr=172.44.0.2 netdev.ipv4_gw_addr=172.44.0.1 netdev.ipv4_subnet_mask=255.255.255.0 --" \
         -cpu host \
         -enable-kvm \
         -nographic
[...]
1: Set IPv4 address 172.44.0.2 mask 255.255.255.0 gw 172.44.0.1
en1: Added
en1: Interface is up
[...]
Listening on port 8123...

Cleaning up means closing the virtual machine (and the HTTP server) and disabling and deleting the virbr0 bridge interface:

$ sudo ip l set dev virbr0 down
$ sudo brctl delbr virbr0

mschlumpp/app-httpreply

HTTP reply on Unikraft