dhcpd

README

Testing DHCP Server

Contents:

• Test setup with Virtual Box
• Quick test with DHCPTest

Test setup with Virtual Box

Prerequisites

To set up a test environment for DHCP server you will need:

• Linux AG Home host machine (Virtual).
• Virtual Box.
• Virtual machine (guest OS doesn't matter).

Configure Virtual Box

1. Install Virtual Box and run the following command to create a Host-Only network:

   $ VBoxManage hostonlyif create
   

   You can check its status by ip a command.

   You can also set up Host-Only network using Virtual Box menu:

   File -> Host Network Manager...
   

2. Create your virtual machine and set up its network:

   VM Settings -> Network -> Host-only Adapter
   

3. Start your VM, install an OS. Configure your network interface to use DHCP and the OS should ask for a IP address from our DHCP server.

4. To see the current IP addresses on client OS you can use ip a command on Linux or ipconfig on Windows.

5. To force the client OS to request an IP from DHCP server again, you can use dhclient on Linux or ipconfig /release on Windows.

Configure server

1. Edit server configuration file AdGuardHome.yaml, for example:

   dhcp:
        enabled: true
        interface_name: vboxnet0
        local_domain_name: lan
        dhcpv4:
          gateway_ip: 192.168.56.1
          subnet_mask: 255.255.255.0
          range_start: 192.168.56.2
          range_end: 192.168.56.2
          lease_duration: 86400
          icmp_timeout_msec: 1000
          options: []
        dhcpv6:
          range_start: 2001::1
          lease_duration: 86400
          ra_slaac_only: false
          ra_allow_slaac: false
   

2. Start the server

   ./AdGuardHome -v
   

   There should be a message in log which shows that DHCP server is ready:

   [info] DHCP: listening on 0.0.0.0:67
   

Quick test with DHCPTest utility

Prerequisites

• DHCP test utility.

Quick test

The DHCP server could be tested for DISCOVER-OFFER packets with in interactive mode.

Documentation

Overview

Package dhcpd provides a DHCP server.

Index

• Constants
• func Create(conf *ServerConfig) (s *server, err error)
• func OptionFQDN(fqdn string) (opt dhcpv4.Option)
• type DHCPServer
• type GetLeasesFlags
• type Interface
• type OnLeaseChangedT
• type ServerConfig
• type V4ServerConf
  • func (c *V4ServerConf) Validate() (err error)
• type V6ServerConf

Constants

const (
	// DefaultDHCPLeaseTTL is the default time-to-live for leases.
	DefaultDHCPLeaseTTL = uint32(timeutil.Day / time.Second)

	// DefaultDHCPTimeoutICMP is the default timeout for waiting ICMP responses.
	DefaultDHCPTimeoutICMP = 1000
)

const (
	LeaseChangedAdded = iota
	LeaseChangedAddedStatic
	LeaseChangedRemovedStatic
	LeaseChangedRemovedAll

	LeaseChangedDBStore
)

flags for onLeaseChanged()

const (
	// ErrDupHostname is returned by addLease, validateStaticLease when the
	// modified lease has a not empty non-unique hostname.
	ErrDupHostname = errors.Error("hostname is not unique")

	// ErrDupIP is returned by addLease, validateStaticLease when the modified
	// lease has a non-unique IP address.
	ErrDupIP = errors.Error("ip address is not unique")
)

const ErrUnconfigured errors.Error = "server is unconfigured"

ErrUnconfigured is returned from the server's method when it requires the server to be configured and it's not.

Functions

func Create

func Create(conf *ServerConfig) (s *server, err error)

Create initializes and returns the DHCP server handling both address families. It also registers the corresponding HTTP API endpoints.

func OptionFQDN

func OptionFQDN(fqdn string) (opt dhcpv4.Option)

OptionFQDN returns a DHCPv4 option for sending the FQDN to the client requested another hostname.

See https://datatracker.ietf.org/doc/html/rfc4702.

Types

type DHCPServer

type DHCPServer interface {
	// ResetLeases resets leases.
	ResetLeases(leases []*dhcpsvc.Lease) (err error)
	// GetLeases returns deep clones of the current leases.
	GetLeases(flags GetLeasesFlags) (leases []*dhcpsvc.Lease)
	// AddStaticLease - add a static lease
	AddStaticLease(l *dhcpsvc.Lease) (err error)
	// RemoveStaticLease - remove a static lease
	RemoveStaticLease(l *dhcpsvc.Lease) (err error)

	// UpdateStaticLease updates IP, hostname of the lease.
	UpdateStaticLease(l *dhcpsvc.Lease) (err error)

	// FindMACbyIP returns a MAC address by the IP address of its lease, if
	// there is one.
	FindMACbyIP(ip netip.Addr) (mac net.HardwareAddr)

	// HostByIP returns a hostname by the IP address of its lease, if there is
	// one.
	HostByIP(ip netip.Addr) (host string)

	// IPByHost returns an IP address by the hostname of its lease, if there is
	// one.
	IPByHost(host string) (ip netip.Addr)

	// WriteDiskConfig4 - copy disk configuration
	WriteDiskConfig4(c *V4ServerConf)
	// WriteDiskConfig6 - copy disk configuration
	WriteDiskConfig6(c *V6ServerConf)

	// Start - start server
	Start() (err error)
	// Stop - stop server
	Stop() (err error)
	// contains filtered or unexported methods
}

DHCPServer - DHCP server interface

type GetLeasesFlags

type GetLeasesFlags uint8

GetLeasesFlags are the flags for GetLeases.

const (
	LeasesDynamic GetLeasesFlags = 0b01
	LeasesStatic  GetLeasesFlags = 0b10

	LeasesAll = LeasesDynamic | LeasesStatic
)

GetLeasesFlags values

type Interface

type Interface interface {
	Start() (err error)
	Stop() (err error)

	// Enabled returns true if the DHCP server is running.
	//
	// TODO(e.burkov):  Currently, we need this method to determine whether the
	// local domain suffix should be considered while resolving A/AAAA requests.
	// This is because other parts of the code aren't aware of the DNS suffixes
	// in DHCP clients names and caller is responsible for trimming it.  This
	// behavior should be changed in the future.
	Enabled() (ok bool)

	// Leases returns all the leases in the database.
	Leases() (leases []*dhcpsvc.Lease)

	// MacByIP returns the MAC address of a client with ip.  It returns nil if
	// there is no such client, due to an assumption that a DHCP client must
	// always have a HardwareAddr.
	MACByIP(ip netip.Addr) (mac net.HardwareAddr)

	// HostByIP returns the hostname of the DHCP client with the given IP
	// address.  The address will be netip.Addr{} if there is no such client,
	// due to an assumption that a DHCP client must always have an IP address.
	HostByIP(ip netip.Addr) (host string)

	// IPByHost returns the IP address of the DHCP client with the given
	// hostname.  The address will be netip.Addr{} if there is no such client,
	// due to an assumption that a DHCP client must always have an IP address.
	IPByHost(host string) (ip netip.Addr)

	WriteDiskConfig(c *ServerConfig)
}

Interface is the DHCP server that deals with both IP address families.

type OnLeaseChangedT

type OnLeaseChangedT func(flags int)

OnLeaseChangedT is a callback for lease changes.

type ServerConfig

type ServerConfig struct {
	// Called when the configuration is changed by HTTP request
	ConfigModified func() `yaml:"-"`

	// Register an HTTP handler
	HTTPRegister aghhttp.RegisterFunc `yaml:"-"`

	Enabled       bool   `yaml:"enabled"`
	InterfaceName string `yaml:"interface_name"`

	// LocalDomainName is the domain name used for DHCP hosts.  For example, a
	// DHCP client with the hostname "myhost" can be addressed as "myhost.lan"
	// when LocalDomainName is "lan".
	//
	// TODO(e.burkov):  Probably, remove this field.  See the TODO on
	// [Interface.Enabled].
	LocalDomainName string `yaml:"local_domain_name"`

	Conf4 V4ServerConf `yaml:"dhcpv4"`
	Conf6 V6ServerConf `yaml:"dhcpv6"`

	// WorkDir is used to store DHCP leases.
	//
	// Deprecated:  Remove it when migration of DHCP leases will not be needed.
	WorkDir string `yaml:"-"`

	// DataDir is used to store DHCP leases.
	DataDir string `yaml:"-"`
	// contains filtered or unexported fields
}

ServerConfig is the configuration for the DHCP server. The order of YAML fields is important, since the YAML configuration file follows it.

type V4ServerConf

type V4ServerConf struct {
	Enabled       bool   `yaml:"-" json:"-"`
	InterfaceName string `yaml:"-" json:"-"`

	GatewayIP  netip.Addr `yaml:"gateway_ip" json:"gateway_ip"`
	SubnetMask netip.Addr `yaml:"subnet_mask" json:"subnet_mask"`

	// The first & the last IP address for dynamic leases
	// Bytes [0..2] of the last allowed IP address must match the first IP
	RangeStart netip.Addr `yaml:"range_start" json:"range_start"`
	RangeEnd   netip.Addr `yaml:"range_end" json:"range_end"`

	LeaseDuration uint32 `yaml:"lease_duration" json:"lease_duration"` // in seconds

	// IP conflict detector: time (ms) to wait for ICMP reply
	// 0: disable
	ICMPTimeout uint32 `yaml:"icmp_timeout_msec" json:"-"`

	// Custom Options.
	//
	// Option with arbitrary hexadecimal data:
	//     DEC_CODE hex HEX_DATA
	// where DEC_CODE is a decimal DHCPv4 option code in range [1..255]
	//
	// Option with IP data (only 1 IP is supported):
	//     DEC_CODE ip IP_ADDR
	Options []string `yaml:"options" json:"-"`
	// contains filtered or unexported fields
}

V4ServerConf - server configuration

func (*V4ServerConf) Validate

func (c *V4ServerConf) Validate() (err error)

Validate returns an error if c is not a valid configuration.

TODO(e.burkov): Don't set the config fields when the server itself will stop containing the config.

type V6ServerConf

type V6ServerConf struct {
	Enabled       bool   `yaml:"-" json:"-"`
	InterfaceName string `yaml:"-" json:"-"`

	// The first IP address for dynamic leases
	// The last allowed IP address ends with 0xff byte
	RangeStart net.IP `yaml:"range_start" json:"range_start"`

	LeaseDuration uint32 `yaml:"lease_duration" json:"lease_duration"` // in seconds

	RASLAACOnly  bool `yaml:"ra_slaac_only" json:"-"`  // send ICMPv6.RA packets without MO flags
	RAAllowSLAAC bool `yaml:"ra_allow_slaac" json:"-"` // send ICMPv6.RA packets with MO flags
	// contains filtered or unexported fields
}

V6ServerConf - server configuration