Add note about ipv4.forward setting in Quick Start guide

[TkrUdagawa]

Hi, thank you for the great project.

While following the Quick Start guide, I found that setting net.ipv4.ip_forward=1 in /etc/sysctl.conf was necessary to enable communication between microVMs.
Additionally, I had to run sudo sysctl -p to apply the change.

It would be helpful if this requirement were mentioned in the documentation, particularly in the Quick Start section, to avoid confusion for other users.

For reference, my environment was:

Platform: AWS EC2

Instance type: c5n.metal

OS image: Ubuntu Server 22.04

[pfandzelter]

Hi @TkrUdagawa, thanks for bringing this up! I'm not sure why this is happening, Celestial should set the required configuration on the host automatically:

celestial/pkg/virt/host.go

Line 41 in 13e7911

// sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

But I should probably set this to use sysctl as all the other commands do, instead of this weird file mangling