odhcp6c - Embedded DHCPv6 Client

Abstract

odhcp6c is a minimal DHCPv6 and RA-client for use in embedded Linux systems especially routers.

Features

1. IPv6 bootstrap from different environments with autodetection

   • RA only
   • RA + stateless DHCPv6
   • RA + stateful DHCPv6 (either IA_NA or IA_PD or both)

2. Handling of non-temporary addresses (IA_NA)

   • handling of valid and preferred lifetimes
   • automatic fallback to stateless or PD-only mode

3. Support for DHCPv6 extension

   • Reconfigure-Messages
   • Prefix Delegation (including handling of valid and preferred lifetimes)
   • Prefix Exclusion
   • DNS Configuration Options
   • NTP Options
   • SIP Options
   • Information-Refresh Options
   • Configurable SOL_MAX_RT
   • DS-Lite AFTR-Name Option
   • Softwire address and port mapped clients (MAP, LW4over6)
   • Server unicast Option

4. Support for requesting and parsing Router Advertisements

   • parsing of prefixes, routes, MTU and RDNSS options

Compiling

odhcp6c 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.

State Script

The state script is called whenever the DHCPv6 state changes. The script is called with the following parameters: <interface> <state>

State	Description
started	The DHCPv6 client has been started
bound	A suitable server was found and addresses or prefixes acquired
informed	A stateless information request returned updated information
updated	Updated information was received from the DHCPv6 server
ra-updated	Updated information was received via Router Advertisements
rebound	The DHCPv6 client switched to another server
unbound	The DHCPv6 client lost all DHCPv6 servers and will restart
stopped	The DHCPv6 client has been stopped

Environment	Description
SERVER	A space-separated list of upstream IPv6 routers
RDNSS	A space-separated list of recursive DNS servers
DOMAINS	A space-separated list of DNS search domains
SNTP_IP	A space-separated list of SNTP server IP addresses
SNTP_FQDN	A space-separated list of SNTP server FQDNs
SIP_IP	A space-separated list of SIP servers
SIP_DOMAIN	A space-separated list of SIP domains
OPTION_<num>	Custom option received as base-16
	E.g. (Client ID) OPTION_1 : 000300010badf00dcafe
PREFIXES	A space-separated list of prefixes currently assigned
	Format: <prefix>/<length>,preferred,valid[,excluded=<excluded-prefix>/<length>][,class=<prefix class #>]
ADDRESSES	A space-separated list of addresses currently assigned
	Format: <address>/<length>,preferred,valid
RA_ADDRESSES	A space-separated list of addresses from RA-prefixes
	Format: <address>/<length>,preferred,valid
RA_ROUTES	A space-separated list of routes from the RA
	Format: <address>/<length>,gateway,valid,metric
RA_DNS	A space-separated list of recursive DNS servers from the RA
RA_DOMAINS	A space-separated list of DNS search domains from the RA
RA_HOPLIMIT	Highest hop-limit received in RAs
RA_MTU	MTU-value received in RA
RA_REACHABLE	ND Reachability time
RA_RETRANSMIT	ND Retransmit time
AFTR	The DS-Lite AFTR domain name
MAPE / MAPT / LW4O6	Softwire rules for MAPE, MAPT and LW4O6
CAPTIVE_PORTAL_URI	RFC8910 captive portal API URI received from upstream
PASSTHRU	The content of the last packet relayed

Ubus Integration

Build with ENABLE_UBUS flag to connect odhcp6c to ubus. Object is registered at : odhcp6c.{ifname}.

Events are emitted whenever the DHCPv6 state changes and can replace the use of a state script. The variables are the same as those defined in the State Script section.

The following RPC methods are available:

Method	I/O	Description
get_state()	Output	Returns the DHCPv6 state
		OUT : see State Script section
get_statistics()	Output	Returns the packet statistics
		dhcp_solicit : Total number of SOLICIT messages sent
		dhcp_advertise : Total number of ADVERTISE messages received
		dhcp_request : Total number of REQUEST messages sent
		dhcp_confirm : Total number of CONFIRM messages sent
		dhcp_renew : Total number of RENEW messages sent
		dhcp_rebind : Total number of REBIND messages sent
		dhcp_reply : Total number of REPLY messages received
		dhcp_release : Total number of RELEASE messages sent
		dhcp_decline : Total number of DECLINE messages sent
		dhcp_reconfigure : Total number of RECONFIGURE messages received
		dhcp_information_request : Total number of INFORMATION-REQUEST messages sent
		dhcp_discarded_packets : Total number of discarded DHCP packets
		dhcp_transmit_failures : Total number of DHCP messages that failed to be transmitted
reset_statistics()	Input	Reset packet statistics
reconfigure_dhcp({...})	Input	Reconfigure DHCP settings
		dscp (int) : DSCP value used for DHCP packets
		release (bool) : Send a RELEASE message on exit/reset
		sol_timeout (int) : Maximum timeout for DHCPv6-SOLICIT
		sk_prio (int) : Packet kernel priority
		opt_requested (int[]) : Options to be requested
		opt_strict (bool) : Do not request any options except those specified
		opt_reconfigure (bool) : Send Accept Reconfigure option
		opt_fqdn (bool) : Send Client FQDN option
		opt_unicast (bool) : Ignore Server Unicast option
		opt_send (string[]) : Options to be sent
		req_addresses (string{`try
		req_prefixes (int) : Request Prefixes (0 = auto)
		stateful_only (bool) : Discard advertisements without any address or prefix proposed
		irt_default (int) : Default information refresh time (expressed in seconds)
		irt_min (int) : Minimum information refresh time (expressed in seconds)
		rand_factor (int) : Randomization factor for retransmission timeout
		auth_protocol (string) : Authentication protocol to be used (None,ConfigurationToken, ReconfigureKeyAuthentication)
		auth_token (string) : Authentication token to be used when AuthenticationProtocol is set to ConfigurationToken
		msg_solicit (table) : Retransmission settings for SOLICIT
		msg_request (table) : Retransmission settings for REQUEST
		msg_renew (table) : Retransmission settings for RENEW
		msg_rebind (table) : Retransmission settings for REBIND
		msg_release (table) : Retransmission settings for RELEASE
		msg_decline (table) : Retransmission settings for DECLINE
		msg_inforeq (table) : Retransmission settings for INFORMATION-REQUEST
		Input arguments for Retransmission settings :
		delay_max (int) : Maximum delay of first message (expressed in seconds)
		timeout_init (int) : Initial message timeout (expressed in seconds)
		timeout_max (int) : Maximum message timeout (expressed in seconds)
		rc_max (int) : Maximum message retry attempts
renew()	Input	Force transmission of RENEW/INFORMATION-REQUEST messages
release()	Input	Force transmission of RELEASE message and start new cycle