* UI shows DHCP configuration screen with "Enabled DHCP" button disabled, and "Check DHCP" button enabled
* User clicks on "Check DHCP"; UI sends request to server
* Server may fail to detect whether there is another DHCP server working in the network. In this case UI shows a warning.
* Server may detect that a dynamic IP configuration is used for this interface. In this case UI shows a warning.
* UI enables "Enable DHCP" button
* User clicks on "Enable DHCP"; UI sends request to server
* Server sets a static IP (if necessary), enables DHCP server, sends the status back to UI
* UI shows the status
### "Check DHCP" command
Request:
POST /control/dhcp/find_active_dhcp
vboxnet0
Response:
200 OK
{
"other_server": {
"found": "yes|no|error",
"error": "Error message", // set if found=error
},
"static_ip": {
"static": "yes|no|error",
"ip": "<CurrentdynamicIPaddress>", // set if static=no
}
}
If `other_server.found` is:
*`no`: everything is fine - there is no other DHCP server
*`yes`: we found another DHCP server. UI shows a warning.
*`error`: we failed to determine whether there's another DHCP server. `other_server.error` contains error details. UI shows a warning.
If `static_ip.static` is:
*`yes`: everything is fine - server uses static IP address.
*`no`: `static_ip.ip` contains the current dynamic IP address which we may set as static. In this case UI shows a warning:
Your system uses dynamic IP address configuration for interface <CURRENTINTERFACENAME>. In order to use DHCP server a static IP address must be set. Your current IP address is <static_ip.ip>. We will automatically set this IP address as static if you press Enable DHCP button.
*`error`: this means that the server failed to check for a static IP. In this case UI shows a warning:
In order to use DHCP server a static IP address must be set. We failed to determine if this network interface is configured using static IP address. Please set a static IP address manually.
### "Enable DHCP" command
Request:
POST /control/dhcp/set_config
{
"enabled":true,
"interface_name":"vboxnet0",
"gateway_ip":"192.169.56.1",
"subnet_mask":"255.255.255.0",
"range_start":"192.169.56.3",
"range_end":"192.169.56.3",
"lease_duration":60,
"icmp_timeout_msec":0
}
Response:
200 OK
OK
### Static IP check/set
Before enabling DHCP server we have to make sure the network interface we use has a static IP configured.
#### Phase 1
On Debian systems DHCP is configured by `/etc/dhcpcd.conf`.
To detect if a static IP is used currently we search for line
interface eth0
and then look for line
static ip_address=...
If the interface already has a static IP, everything is set up, we don't have to change anything.
To get the current IP address along with netmask we execute
On Ubuntu DHCP for a network interface can't be disabled via `dhcpcd.conf`. This must be configured in `/etc/netplan/01-netcfg.yaml`.
Fedora doesn't use `dhcpcd.conf` configuration at all.
Step 1.
To set a static IP address we add these lines to `dhcpcd.conf`:
interface eth0
static ip_address=192.168.0.1/24
static routers=192.168.0.1
static domain_name_servers=192.168.0.1
* Don't set 'routers' if we couldn't find gateway IP
* Set 'domain_name_servers' equal to our IP
Step 2.
If we would set a different IP address, we'd need to replace the IP address for the current network configuration. But currently this step isn't necessary.
When a client requests information from DNS server, he's identified by IP address.
Administrator can set a name for a client with a known IP and also override global settings for this client. The name is used to improve readability of DNS logs: client's name is shown in UI next to its IP address. The names are loaded from 3 sources:
* automatically from "/etc/hosts" file. It's a list of `IP<->Name` entries which is loaded once on AGH startup from "/etc/hosts" file.
* automatically using rDNS. It's a list of `IP<->Name` entries which is added in runtime using rDNS mechanism when a client first makes a DNS request.
* manually configured via UI. It's a list of client's names and their settings which is loaded from configuration file and stored on disk.
### Per-client settings
UI provides means to manage the list of known clients (List/Add/Update/Delete) and their settings. These settings are stored in configuration file as an array of objects.
Notes:
*`name`, `ip` and `mac` values are unique.
*`ip`&`mac` values can't be set both at the same time.
* If `mac` is set and DHCP server is enabled, IP is taken from DHCP lease table.
* If `use_global_settings` is true, then DNS responses for this client are processed and filtered using global settings.
* If `use_global_settings` is false, then the client-specific settings are used to override (disable) global settings. For example, if global setting `parental_enabled` is true, then per-client setting `parental_enabled:false` can disable Parental Control for this specific client.
