dhcp.c

lwip-1.4.0

/**
 * @file
 * Dynamic Host Configuration Protocol client
 *
 */

/*
 *
 * Copyright (c) 2001-2004 Leon Woestenberg <[e-mail]>
 * Copyright (c) 2001-2004 Axon Digital Design B.V., The Netherlands.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is a contribution to the lwIP TCP/IP stack.
 * The Swedish Institute of Computer Science and Adam Dunkels
 * are specifically granted permission to redistribute this
 * source code.
 *
 * Author: Leon Woestenberg <[e-mail]>
 *
 * This is a DHCP client for the lwIP TCP/IP stack. It aims to conform
 * with RFC 2131 and RFC 2132.
 *
 * TODO:
 * - Support for interfaces other than Ethernet (SLIP, PPP, ...)
 *
 * Please coordinate changes and requests with Leon Woestenberg
 * <[e-mail]>
 *
 * Integration with your code:
 *
 * In lwip/dhcp.h
 * #define DHCP_COARSE_TIMER_SECS (recommended 60 which is a minute)
 * #define DHCP_FINE_TIMER_MSECS (recommended 500 which equals TCP coarse timer)
 *
 * Then have your application call dhcp_coarse_tmr() and
 * dhcp_fine_tmr() on the defined intervals.
 *
 * dhcp_start(struct netif *netif);
 * starts a DHCP client instance which configures the interface by
 * obtaining an IP address lease and maintaining it.
 *
 * Use dhcp_release(netif) to end the lease and use dhcp_stop(netif)
 * to remove the DHCP client.
 *
 */

#include "lwip/opt.h"

#if LWIP_DHCP /* don't build if not configured for use in lwipopts.h */

#include "lwip/stats.h"
#include "lwip/mem.h"
#include "lwip/udp.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/def.h"
#include "lwip/sys.h"
#include "lwip/dhcp.h"
#include "lwip/autoip.h"
#include "lwip/dns.h"
#include "netif/etharp.h"

#include <string.h>

/** Default for DHCP_GLOBAL_XID is 0xABCD0000
 * This can be changed by defining DHCP_GLOBAL_XID and DHCP_GLOBAL_XID_HEADER, e.g.
 *  #define DHCP_GLOBAL_XID_HEADER "stdlib.h"
 *  #define DHCP_GLOBAL_XID rand()
 */
#ifdef DHCP_GLOBAL_XID_HEADER
#include DHCP_GLOBAL_XID_HEADER /* include optional starting XID generation prototypes */
#endif

/** DHCP_OPTION_MAX_MSG_SIZE is set to the MTU
 * MTU is checked to be big enough in dhcp_start */
#define DHCP_MAX_MSG_LEN(netif)        (netif->mtu)
#define DHCP_MAX_MSG_LEN_MIN_REQUIRED  576
/** Minimum length for reply before packet is parsed */
#define DHCP_MIN_REPLY_LEN             44

#define REBOOT_TRIES 2

/** Option handling: options are parsed in dhcp_parse_reply
 * and saved in an array where other functions can load them from.
 * This might be moved into the struct dhcp (not necessarily since
 * lwIP is single-threaded and the array is only used while in recv
 * callback). */
#define DHCP_OPTION_IDX_OVERLOAD    0
#define DHCP_OPTION_IDX_MSG_TYPE    1
#define DHCP_OPTION_IDX_SERVER_ID   2
#define DHCP_OPTION_IDX_LEASE_TIME  3
#define DHCP_OPTION_IDX_T1          4
#define DHCP_OPTION_IDX_T2          5
#define DHCP_OPTION_IDX_SUBNET_MASK 6
#define DHCP_OPTION_IDX_ROUTER      7
#define DHCP_OPTION_IDX_DNS_SERVER	8
#define DHCP_OPTION_IDX_MAX         (DHCP_OPTION_IDX_DNS_SERVER + DNS_MAX_SERVERS)

/** Holds the decoded option values, only valid while in dhcp_recv.
    @todo: move this into struct dhcp? */
u32_t dhcp_rx_options_val[DHCP_OPTION_IDX_MAX];
/** Holds a flag which option was received and is contained in dhcp_rx_options_val,
    only valid while in dhcp_recv.
    @todo: move this into struct dhcp? */
u8_t  dhcp_rx_options_given[DHCP_OPTION_IDX_MAX];

#define dhcp_option_given(dhcp, idx)          (dhcp_rx_options_given[idx] != 0)
#define dhcp_got_option(dhcp, idx)            (dhcp_rx_options_given[idx] = 1)
#define dhcp_clear_option(dhcp, idx)          (dhcp_rx_options_given[idx] = 0)
#define dhcp_clear_all_options(dhcp)          (memset(dhcp_rx_options_given, 0, sizeof(dhcp_rx_options_given)))
#define dhcp_get_option_value(dhcp, idx)      (dhcp_rx_options_val[idx])
#define dhcp_set_option_value(dhcp, idx, val) (dhcp_rx_options_val[idx] = (val))


/* DHCP client state machine functions */
static err_t dhcp_discover(struct netif *netif);
static err_t dhcp_select(struct netif *netif);
static void dhcp_bind(struct netif *netif);
#if DHCP_DOES_ARP_CHECK
static err_t dhcp_decline(struct netif *netif);
#endif /* DHCP_DOES_ARP_CHECK */
static err_t dhcp_rebind(struct netif *netif);
static err_t dhcp_reboot(struct netif *netif);
static void dhcp_set_state(struct dhcp *dhcp, u8_t new_state);

/* receive, unfold, parse and free incoming messages */
static void dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);

/* set the DHCP timers */
static void dhcp_timeout(struct netif *netif);
static void dhcp_t1_timeout(struct netif *netif);
static void dhcp_t2_timeout(struct netif *netif);

/* build outgoing messages */
/* create a DHCP message, fill in common headers */
static err_t dhcp_create_msg(struct netif *netif, struct dhcp *dhcp, u8_t message_type);
/* free a DHCP request */
static void dhcp_delete_msg(struct dhcp *dhcp);
/* add a DHCP option (type, then length in bytes) */
static void dhcp_option(struct dhcp *dhcp, u8_t option_type, u8_t option_len);
/* add option values */
static void dhcp_option_byte(struct dhcp *dhcp, u8_t value);
static void dhcp_option_short(struct dhcp *dhcp, u16_t value);
static void dhcp_option_long(struct dhcp *dhcp, u32_t value);
/* always add the DHCP options trailer to end and pad */
static void dhcp_option_trailer(struct dhcp *dhcp);

/**
 * Back-off the DHCP client (because of a received NAK response).
 *
 * Back-off the DHCP client because of a received NAK. Receiving a
 * NAK means the client asked for something non-sensible, for
 * example when it tries to renew a lease obtained on another network.
 *
 * We clear any existing set IP address and restart DHCP negotiation
 * afresh (as per RFC2131 3.2.3).
 *
 * @param netif the netif under DHCP control
 */
static void
dhcp_handle_nak(struct netif *netif)
{
  struct dhcp *dhcp = netif->dhcp;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_handle_nak(netif=%p) %c%c%"U16_F"\n", 
    (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num));
  /* Set the interface down since the address must no longer be used, as per RFC2131 */
  netif_set_down(netif);
  /* remove IP address from interface */
  netif_set_ipaddr(netif, IP_ADDR_ANY);
  netif_set_gw(netif, IP_ADDR_ANY);
  netif_set_netmask(netif, IP_ADDR_ANY); 
  /* Change to a defined state */
  dhcp_set_state(dhcp, DHCP_BACKING_OFF);
  /* We can immediately restart discovery */
  dhcp_discover(netif);
}

#if DHCP_DOES_ARP_CHECK
/**
 * Checks if the offered IP address is already in use.
 *
 * It does so by sending an ARP request for the offered address and
 * entering CHECKING state. If no ARP reply is received within a small
 * interval, the address is assumed to be free for use by us.
 *
 * @param netif the netif under DHCP control
 */
static void
dhcp_check(struct netif *netif)
{
  struct dhcp *dhcp = netif->dhcp;
  err_t result;
  u16_t msecs;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_check(netif=%p) %c%c\n", (void *)netif, (s16_t)netif->name[0],
    (s16_t)netif->name[1]));
  dhcp_set_state(dhcp, DHCP_CHECKING);
  /* create an ARP query for the offered IP address, expecting that no host
     responds, as the IP address should not be in use. */
  result = etharp_query(netif, &dhcp->offered_ip_addr, NULL);
  if (result != ERR_OK) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("dhcp_check: could not perform ARP query\n"));
  }
  dhcp->tries++;
  msecs = 500;
  dhcp->request_timeout = (msecs + DHCP_FINE_TIMER_MSECS - 1) / DHCP_FINE_TIMER_MSECS;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("dhcp_check(): set request timeout %"U16_F" msecs\n", msecs));
}
#endif /* DHCP_DOES_ARP_CHECK */

/**
 * Remember the configuration offered by a DHCP server.
 *
 * @param netif the netif under DHCP control
 */
static void
dhcp_handle_offer(struct netif *netif)
{
  struct dhcp *dhcp = netif->dhcp;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_handle_offer(netif=%p) %c%c%"U16_F"\n",
    (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num));
  /* obtain the server address */
  if (dhcp_option_given(dhcp, DHCP_OPTION_IDX_SERVER_ID)) {
    ip4_addr_set_u32(&dhcp->server_ip_addr, htonl(dhcp_get_option_value(dhcp, DHCP_OPTION_IDX_SERVER_ID)));
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_STATE, ("dhcp_handle_offer(): server 0x%08"X32_F"\n",
      ip4_addr_get_u32(&dhcp->server_ip_addr)));
    /* remember offered address */
    ip_addr_copy(dhcp->offered_ip_addr, dhcp->msg_in->yiaddr);
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_STATE, ("dhcp_handle_offer(): offer for 0x%08"X32_F"\n",
      ip4_addr_get_u32(&dhcp->offered_ip_addr)));

    dhcp_select(netif);
  } else {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_SERIOUS,
      ("dhcp_handle_offer(netif=%p) did not get server ID!\n", (void*)netif));
  }
}

/**
 * Select a DHCP server offer out of all offers.
 *
 * Simply select the first offer received.
 *
 * @param netif the netif under DHCP control
 * @return lwIP specific error (see error.h)
 */
static err_t
dhcp_select(struct netif *netif)
{
  struct dhcp *dhcp = netif->dhcp;
  err_t result;
  u16_t msecs;

  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_select(netif=%p) %c%c%"U16_F"\n", (void*)netif, netif->name[0], netif->name[1], (u16_t)netif->num));
  dhcp_set_state(dhcp, DHCP_REQUESTING);

  /* create and initialize the DHCP message header */
  result = dhcp_create_msg(netif, dhcp, DHCP_REQUEST);
  if (result == ERR_OK) {
    dhcp_option(dhcp, DHCP_OPTION_MAX_MSG_SIZE, DHCP_OPTION_MAX_MSG_SIZE_LEN);
    dhcp_option_short(dhcp, DHCP_MAX_MSG_LEN(netif));

    /* MUST request the offered IP address */
    dhcp_option(dhcp, DHCP_OPTION_REQUESTED_IP, 4);
    dhcp_option_long(dhcp, ntohl(ip4_addr_get_u32(&dhcp->offered_ip_addr)));

    dhcp_option(dhcp, DHCP_OPTION_SERVER_ID, 4);
    dhcp_option_long(dhcp, ntohl(ip4_addr_get_u32(&dhcp->server_ip_addr)));

    dhcp_option(dhcp, DHCP_OPTION_PARAMETER_REQUEST_LIST, 4/*num options*/);
    dhcp_option_byte(dhcp, DHCP_OPTION_SUBNET_MASK);
    dhcp_option_byte(dhcp, DHCP_OPTION_ROUTER);
    dhcp_option_byte(dhcp, DHCP_OPTION_BROADCAST);
    dhcp_option_byte(dhcp, DHCP_OPTION_DNS_SERVER);

#if LWIP_NETIF_HOSTNAME
    if (netif->hostname != NULL) {
      const char *p = (const char*)netif->hostname;
      u8_t namelen = (u8_t)strlen(p);
      if (namelen > 0) {
        LWIP_ASSERT("DHCP: hostname is too long!", namelen < 255);
        dhcp_option(dhcp, DHCP_OPTION_HOSTNAME, namelen);
        while (*p) {
          dhcp_option_byte(dhcp, *p++);
        }
      }
    }
#endif /* LWIP_NETIF_HOSTNAME */

    dhcp_option_trailer(dhcp);
    /* shrink the pbuf to the actual content length */
    pbuf_realloc(dhcp->p_out, sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN + dhcp->options_out_len);

    /* send broadcast to any DHCP server */
    udp_sendto_if(dhcp->pcb, dhcp->p_out, IP_ADDR_BROADCAST, DHCP_SERVER_PORT, netif);
    dhcp_delete_msg(dhcp);
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("dhcp_select: REQUESTING\n"));
  } else {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("dhcp_select: could not allocate DHCP request\n"));
  }
  dhcp->tries++;
  msecs = (dhcp->tries < 6 ? 1 << dhcp->tries : 60) * 1000;
  dhcp->request_timeout = (msecs + DHCP_FINE_TIMER_MSECS - 1) / DHCP_FINE_TIMER_MSECS;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_STATE, ("dhcp_select(): set request timeout %"U16_F" msecs\n", msecs));
  return result;
}

/**
 * The DHCP timer that checks for lease renewal/rebind timeouts.
 */
void
dhcp_coarse_tmr()
{
  struct netif *netif = netif_list;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_coarse_tmr()\n"));
  /* iterate through all network interfaces */
  while (netif != NULL) {
    /* only act on DHCP configured interfaces */
    if (netif->dhcp != NULL) {
      /* timer is active (non zero), and triggers (zeroes) now? */
      if (netif->dhcp->t2_timeout-- == 1) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("dhcp_coarse_tmr(): t2 timeout\n"));
        /* this clients' rebind timeout triggered */
        dhcp_t2_timeout(netif);
      /* timer is active (non zero), and triggers (zeroes) now */
      } else if (netif->dhcp->t1_timeout-- == 1) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_STATE, ("dhcp_coarse_tmr(): t1 timeout\n"));
        /* this clients' renewal timeout triggered */
        dhcp_t1_timeout(netif);