api-reference.md

dmdhcp API Reference

See include/dmdhcp.h for the authoritative declarations and doc comments - this page is a navigable summary. See dmdhcp.md for the architecture (threading, locking, the RFC 2131 state machine).

Types

Type	Description
dmdhcp_lease_t	Opaque handle to one lease's lifecycle on one interface.
dmdhcp_state_t	RFC 2131 §4.4 client state, plus dmdhcp's own conflict-probe/decline-backoff states.
dmdhcp_callbacks_t	on_bound / on_expired_or_lost / on_error.
dmdhcp_options_t	Optional hostname + INIT-REBOOT remembered address, passed to dmdhcp_start().
dmdhcp_lease_info_t	Snapshot of the active lease's address/netmask/gateway/server/lease-time.
dmdhcp_message_t	Parsed DHCP/BOOTP fixed header fields (RFC 2131 §2).
dmdhcp_option_t	One parsed RFC 2132 TLV option.
dmdhcp_msg_type_t	DHCPDISCOVER..DHCPINFORM (option 53 values).

Functions

Lease lifecycle

Function	Description
dmdhcp_start()	Begin acquiring a lease on an interface.
dmdhcp_set_callbacks()	Replace a lease's callbacks/user_data.
dmdhcp_renew()	Force dmdhcp_state_bound -> _renewing immediately.
dmdhcp_release()	Send DHCPRELEASE, de-configure the interface, free the lease.
dmdhcp_stop()	De-configure and free the lease without sending DHCPRELEASE.

Accessors

Function	Description
dmdhcp_get_state()	Current dmdhcp_state_t.
dmdhcp_get_iface()	The interface this lease was started on.
dmdhcp_get_user_data()	The user_data most recently set.
dmdhcp_get_xid()	Current transaction ID (diagnostics/testing).
dmdhcp_get_lease_info()	Snapshot of address/netmask/gateway/server/lease-time - -EINVAL unless BOUND/RENEWING/REBINDING.
dmdhcp_get_dns_server_count() / dmdhcp_get_dns_server()	The DHCP-offered DNS server list (option 6) - dmdhcp is the only owner of DNS configuration storage in this ecosystem.

DIF implementations

DIF	Description
dmdns_provide_servers (dmdns)	Reports, through dmdns's sink, the option 6 servers of every lease that is BOUND, RENEWING or REBINDING. Asked by dmdns on every lookup; dmdns is not a required module of dmdhcp.

Wire codec (usable independently of a lease)

Function	Description
dmdhcp_build_message() / dmdhcp_parse_message()	Fixed BOOTP/DHCP header + magic cookie.
dmdhcp_options_write() / dmdhcp_options_find()	RFC 2132 TLV options.
dmdhcp_option_get_u32() / _get_addr() / _addr_count() / _get_addr_at()	Decode a found option's payload.

Constants

Constant	Value	Meaning
DMDHCP_SERVER_PORT	67
DMDHCP_CLIENT_PORT	68
DMDHCP_MAGIC_COOKIE	0x63825363	RFC 2132 §9.1
DMDHCP_OPT_*	-	Option codes dmdhcp reads/writes (subnet mask, router, DNS server, hostname, requested IP, lease time, msg type, server ID, T1, T2, end).