OpenWrt DHCP Server (mirror)

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odhcpd - Embedded DHCP/DHCPv6/RA Server & Relay

** Abstract **

odhcpd is a daemon for serving and relaying IP management protocols to
configure clients and downstream routers. It tries to follow the RFC 6204
requirements for IPv6 home routers.

odhcpd provides server services for DHCP, RA, stateless and stateful DHCPv6,
prefix delegation and can be used to relay RA, DHCPv6 and NDP between routed
(non-bridged) interfaces in case no delegated prefixes are available.

** Features **

1. Router Discovery support (solicitations and advertisements) with 2 modes
server: RD server for slave interfaces
a) automatic detection of prefixes, delegated prefix and default routes, MTU
b) automatic reannouncement when changes to prefixes or routes occur

relay: RD relay between master and slave interfaces
a) support for rewriting announced DNS-server addresses in relay mode

2. DHCPv6-support with 2 modes of operation
server: stateless, stateful and PD-server mode
a) stateless and stateful address assignment
b) prefix delegation support
c) dynamic reconfiguration in case prefixes change
d) hostname detection and hosts-file creation

relay: mostly standards-compliant DHCPv6-relay
a) support for rewriting announced DNS-server addresses

3. DHCPv4-support
server: stateless and stateful mode

4. Proxy for Neighbor Discovery messages (solicitations and advertisements)
a) support for auto-learning routes to the local routing table
b) support for marking interfaces "external" not proxying NDP for them
and only serving NDP for DAD and for traffic to the router itself
[Warning: you should provide additional firewall rules for security]

** Compiling **

odhcpd uses cmake:
* To prepare a Makefile use: "cmake ."
* To build / install use: "make" / "make install" afterwards.
* To build DEB or RPM packages use: "make package" afterwards.

** Configuration **

odhcpd uses a UCI configuration file in /etc/config/dhcp for configuration
and may also receive information from ubus

Section of type odhcpd

Option Type Default Description
legacy bool 0 Enable DHCPv4 if start but
no dhcpv4 option set
maindhcp bool 0 Use odhcpd as the main DHCPv4
leasefile string DHCP/v6 lease/hostfile
leasetrigger string Lease trigger script
hostsfile string DHCP/v6 hostfile
loglevel integer 6 Syslog level priority (0-7)

Sections of type dhcp (configure DHCP / DHCPv6 / RA / NDP service)

Option Type Default Description
interface string logical OpenWrt interface
ifname string physical network interface
networkid string same as ifname compat. alias for ifname
master bool 0 is a master interface
for relaying

ra string disabled Router Advert service
dhcpv6 string disabled DHCPv6 service
dhcpv4 string disabled DHCPv4 service
ndp string disabled Neighbor Discovery Proxy

dynamicdhcp bool 1 Dynamically create leases
for DHCPv4 and DHCPv6
dhcpv4_forcereconf bool 0 Force reconfiguration by sending
force renew message even if the client
did not include the force renew nonce
capability option (RFC6704)
dhcpv6_assignall bool 1 Assign all viable DHCPv6 addresses
in statefull mode; if disabled
only the DHCPv6 address having the
longest preferred lifetime is assigned
dhcpv6_hostidlength integer 12 Host ID length of dynamically created leases,
allowed values: 12 - 64 (bits).
dhcpv6_na bool 1 DHCPv6 stateful addressing hands out IA_NA -
Internet Address - Network Address
dhcpv6_pd bool 1 DHCPv6 stateful addressing hands out IA_PD -
Internet Address - Prefix Delegation
dhcpv6_pd_min_len integer - Minimum prefix length to delegate with IA_PD
(value is adjusted if needed to be greater
than the interface prefix length). Range [1,62]
router list Routers to announce
accepts IPv4 only
dns list DNS servers to announce
accepts IPv4 and IPv6
dns_service bool 1 Announce the address of interface as DNS service
if the list of dns is empty
domain list Search domains to announce

leasetime string 12h DHCPv4 address leasetime
start integer 100 DHCPv4 pool start
limit integer 150 DHCPv4 pool size
preferred_lifetime string 12h Value for the preferred lifetime
for a prefix
ra_default integer 0 Override default route
0: default, 1: ignore no public address, 2: ignore all
ra_flags list other-config List of RA flags to be
advertised in RA messages
[managed-config other-config home-agent none]
ra_slaac bool 1 Announce slaac for a prefix
ra_offlink bool 0 Announce prefixes off-link
ra_preference string medium Route(r) preference
ra_maxinterval integer 600 Maximum time allowed between
sending unsolicited RA
ra_mininterval integer 200 Minimum time allowed between
sending unsolicited RA
ra_lifetime integer 1800 Value to be placed in Router
Lifetime field of RA
ra_useleasetime bool 0 Use configured leasetime as
limit for the preferred and
valid lifetime of a prefix
ra_reachabletime integer 0 Reachable Time in milliseconds to be
advertised in RA messages
ra_retranstime integer 0 Retransmit Time in milliseconds to be
advertised in RA messages
ra_hoplimit integer 0 Current hoplimit to be advertised
in RA messages
ra_mtu integer - MTU to be advertised in
RA messages
ra_dns bool 1 Announce DNS configuration in
RA messages (RFC8106)
ra_pref64 string Announce PREF64 option
[IPv6 prefix] for NAT64 prefix (RFC8781)
ndproxy_routing bool 1 Learn routes from NDP
ndproxy_slave bool 0 NDProxy external slave
prefix_filter string ::/0 Only advertise on-link prefixes within
[IPv6 prefix] the provided IPv6 prefix; others are
filtered out.
ntp list NTP servers to announce
accepts IPv4 and IPv6

Sections of type host (static leases)
Option Type Default Description
ip string IP-Address to lease
mac string MAC-address
duid string DUID in base16
hostid string IPv6 host identifier
name string Hostname
leasetime string DHCPv4/v6 leasetime