Add network config devices

[vinc]

• Add net-gw device
• Add net-ip device
• Add net-mac device
• Add net-usage device

[vinc]

We can now configure the network manually from userspace:

[vinc]

The format for /dev/net/usage is: <recv packets> <recv bytes> <sent packets> <sent bytes>

~
> dhcp
[248.908097] NET IP 10.0.2.15/24
[248.916096] NET GW 10.0.2.2
[248.926094] NET DNS 10.0.2.3

~
> read /dev/net/usage
2 1180 2 620

~
> http example.com => /dev/null

~
> read /dev/net/usage
10 3312 10 1151

[vinc]

The failing test on the previous commit due to memory allocation failure was weird.

[vinc]

The device system could be refactored to be more hierarchical in the future instead of having just one big flat enum. For example all the net-* devices could be grouped into a virtual net device, sharing the same first byte on the device file, and then the second byte of the file would be used by the net module to dispatch the IO commands to the right IO NET device.

The ATA devices already use the next two bytes for the bus and drive numbers so there's a precedent for that.

[vinc]

We'll need a way to monitor all network traffic and enable/disable the debug mode before removing the net command completely.