router7/website/content/architecture.md

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Architecture

router7 is based on gokrazy: it is an appliance which gets packed into a hard disk image, containing a FAT partition with the kernel, a read-only SquashFS partition for the root file system and an ext4 partition for permanent data.

The individual services can be found in github.com/rtr7/router7/cmd

• Each service runs in a separate process.
• Services communicate with each other by persisting state files. E.g., cmd/dhcp4 writes /perm/dhcp4/wire/lease.json.
• A service notifies other services about state changes by sending them signal SIGUSR1.

Configuration files

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File	Consumer(s)	Purpose
/perm/interfaces.json	netconfigd	Set IP/MAC addresses of uplink0 and lan0
/perm/portforwardings.json	netconfigd	Configure nftables port forwarding rules
/perm/dhcp6/duid	dhcp6	Set DHCP Unique Identifier (DUID) for obtaining static leases
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State files

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File	Producer	Consumer(s)	Purpose
/perm/dhcp4/wire/ack	dhcp4	dhcp4	last DHCPACK packet for renewals across restarts
/perm/dhcp4/wire/lease.json	dhcp4	netconfigd	Obtained DHCPv4 lease
/perm/dhcp6/wire/lease.json	dhcp6	netconfigd, radvd	Obtained DHCPv6 lease
/perm/dhcp4d/leases.json	dhcp4d	dhcp4d, dnsd	DHCPv4 leases handed out (including hostnames)
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Available ports

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Port	Purpose
<public>:8053	dnsd metrics (forwarded requests)
<public>:8066	netconfigd metrics (nftables counters)
<private>:80	gokrazy web interface
<private>:67	dhcp4d
<private>:58	radvd
<private>:53	dnsd
<private>:8077	backupd (serve backup.tar.gz)
<private>:7733	diagd (perform diagnostics)
<private>:5022	captured (serve captured packets)
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Here’s an example of cmd/diagd output:

Here’s an example of cmd/netconfigd metrics when scraped with Prometheus and displayed in Grafana: