dmdhcp

dmdhcp DMOD library module.

Description

dmdhcp is a DHCP client (RFC 2131/2132) for the DMOD network stack. It does not implement a DHCP server.

One dmdhcp_lease_t represents the whole lease lifecycle (DISCOVER/OFFER/ REQUEST/ACK, renewal, rebinding, release) for one interface. On acquiring or renewing a lease, dmdhcp applies it to the interface itself (address/netmask/broadcast plus a default route) and reverts that on release/expiry - a caller does not need to configure the interface by hand. Address-conflict detection (RFC 2131 §4.4.1, an ARP probe before committing an address) is included.

dmdhcp keeps no thread of its own: inbound messages are processed inline on whatever thread is already pumping the interface (via dmudp_bind()), and time-driven behavior (retransmission backoff, the conflict probe, lease timers) runs on dmosi_timer_t callbacks. See docs/dmdhcp.md for the full architecture.

Building

Using CMake

mkdir -p build
cd build
cmake ..
cmake --build .

Pass -DDMOD_DIR=/path/to/local/dmod to build against a local dmod checkout instead of fetching develop from GitHub.

Using Make

make DMOD_MODE=DMOD_MODULE DMOD_DIR=/path/to/dmod

Testing

Tests are built automatically alongside the module (see tests/). Once built, run them with ctest:

cd build
ctest --output-on-failure

ctest installs the test module's dependencies with dmf-get and then runs it through dmod_loader. To run it manually instead:

export DMOD_DMF_DIR=$(pwd)/build/dmf
dmf-get install -d ${DMOD_DMF_DIR}/test_dmdhcp-local.dmd -y
dmod_loader build/dmf/test_dmdhcp.dmf

Usage

#include "dmdhcp.h"

static void on_bound(dmdhcp_lease_t lease, bool is_renewal, void* user_data)
{
    dmdhcp_lease_info_t info;
    dmdhcp_get_lease_info(lease, &info);
    /* info.ip_address / .netmask / .gateway are already applied to the
     * interface at this point - nothing further to configure. */
}

static void on_lost(dmdhcp_lease_t lease, void* user_data)
{
    /* NAK'd or the lease fully expired - the interface has already been
     * de-configured. dmdhcp restarts DISCOVER on its own. */
}

dmdhcp_callbacks_t callbacks = { .on_bound = on_bound, .on_expired_or_lost = on_lost };
dmdhcp_lease_t lease = dmdhcp_start(iface, &callbacks, NULL, NULL);

API

Function	Description
dmdhcp_start()	Begin acquiring a lease on an interface; keeps renewing/rebinding/restarting automatically.
dmdhcp_set_callbacks()	Replace a lease's callbacks/user_data.
dmdhcp_renew()	Force an immediate renewal attempt.
dmdhcp_release()	Send DHCPRELEASE, de-configure the interface, free the lease.
dmdhcp_stop()	De-configure and free the lease without sending DHCPRELEASE.
dmdhcp_get_state() / _get_iface() / _get_user_data() / _get_xid()	Simple accessors.
dmdhcp_get_lease_info()	Snapshot of the active lease's address/netmask/gateway/server/lease-time.
dmdhcp_get_dns_server_count() / _get_dns_server()	The DHCP-offered DNS server list.
dmdhcp_build_message() / _parse_message()	DHCP/BOOTP fixed header codec (RFC 2131 §2).
dmdhcp_options_write() / _options_find() / _option_get_*()	RFC 2132 TLV options codec.

See include/dmdhcp.h for the full declarations and docs/api-reference.md for the complete reference.

Documentation

See the docs/ directory:

• api-reference.md - Complete API documentation

View documentation using dmf-man dmdhcp.

Project Structure

dmdhcp/
├── docs/                      # Documentation (markdown format)
│   ├── README.md
│   ├── api-reference.md
│   └── dmdhcp.md              # Architecture: threading, locking, state machine
├── include/                   # Public headers
│   └── dmdhcp.h
├── src/
│   ├── dmdhcp_internal.h      # Private struct dmdhcp_lease, constants
│   ├── dmdhcp.c               # dmod_init()/_deinit(), _start()/_stop()/_release()/_renew()
│   ├── dmdhcp_registrations.c # DMOD_ENABLE_REGISTRATION (must stand alone)
│   ├── dmdhcp_lease_table.c   # Lease table CRUD, teardown, simple accessors
│   ├── dmdhcp_wire.c          # DHCP/BOOTP fixed header codec
│   ├── dmdhcp_options.c       # RFC 2132 TLV options codec
│   ├── dmdhcp_output.c        # Message senders + retransmit/probe timer
│   ├── dmdhcp_input.c         # dmudp_bind() registration + dispatch
│   └── dmdhcp_lifecycle.c     # Apply/unapply to interface + lease timer
├── tests/
│   ├── CMakeLists.txt
│   └── dmdhcp_test.c
├── CMakeLists.txt
├── Makefile
├── dmdhcp.dmr
└── manifest.dmm

Author

Patryk Kubiak

License

MIT