DHCP server

For the boxes that do not let you change the DNS server they give (Livebox, SFR Box), Warda can give the addresses of the network itself: each device then gets Warda as DNS server, and the box as gateway. It is off by default; the installation assistant (or Network → DHCP, Set up) turns it on in three steps:

1. the address of Warda must be fixed: on the Raspberry Pi image (or any Debian machine run by NetworkManager), warda-system.service makes the current address permanent with nmcli; elsewhere, fix it by hand;
2. turn the DHCP server of the box off;
3. Warda checks that no other server answers (a discovery relayed from Warda itself, answered to it on port 67), then restarts with its DHCP server on.

It gives the addresses of the network of the box from the 20th to 5 before the last, for 24 hours, never an address in the ARP table of another machine: first an address never given, searched from the one after the last address offered, then the one expired longest ago. While 1024 offers are pending (an offer is kept a minute), the discoveries of new clients get no answer. Network → DHCP, Set up changes the range (inside the network, without the address of Warda nor of the box) and the lease (1 hour to 7 days); Warda restarts to apply them (WARDA_DHCP_RANGE=start-end and WARDA_DHCP_LEASE fix them). Addresses can be reserved for a device from Network → DHCP. The devices get a name under the local domain (their name in Warda, else the one they give), answered by Warda, and warda.<domain> is Warda itself. The machines found on the network (network scan, clients seen in the last 24 hours) get a name too, at their current IPv4 address, even without the DHCP server of Warda, refreshed every minute: their own name, else what they are (laserjet-m110), else their maker and the end of their address (samsung-23, device-23), with the end of their address when two have the same name; the names of the DHCP server come first. The local domain is chosen from the language at installation (home.lan, maison.lan, haus.lan, casa.lan, thuis.lan) and changed in Network → Local DNS (WARDA_LOCAL_DOMAIN fixes it); it ends with .lan, .home.arpa, .internal or .home, never .local (multicast DNS). As soon as it hears another DHCP server (a client choosing it, or an answer to the discovery it sends every 5 minutes), Warda stops giving addresses until that server is gone. If the Warda box stops for good, turn the DHCP server of the box on again: the devices keep their address a day.

A box that announces its own DNS server over IPv6 (Router Advertisements) lets the devices go around Warda: Warda shows it from the resolvers of its machine, and the assistant tells to turn IPv6, or its DNS server, off on the box. WARDA_DHCP=true turns the server on from the configuration.