dhcp.c

基于STM32F107的UDP服务器程序

    if (dhcp->options_in == NULL) {
      LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("dhcp_unfold_reply(): could not allocate dhcp->options\n"));
      return ERR_MEM;
    }
  }
  dhcp->msg_in = mem_malloc(sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN);
  if (dhcp->msg_in == NULL) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("dhcp_unfold_reply(): could not allocate dhcp->msg_in\n"));
    mem_free((void *)dhcp->options_in);
    dhcp->options_in = NULL;
    return ERR_MEM;
  }

  /** copy the DHCP message without options */
  ret = pbuf_copy_partial(dhcp->p, dhcp->msg_in, sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN, 0);
  LWIP_ASSERT("ret == sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN", ret == sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN);
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_unfold_reply(): copied %"U16_F" bytes into dhcp->msg_in[]\n",
     sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN));

  if (dhcp->options_in != NULL) {
    /** copy the DHCP options */
    ret = pbuf_copy_partial(dhcp->p, dhcp->options_in, dhcp->options_in_len, sizeof(struct dhcp_msg) - DHCP_OPTIONS_LEN);
    LWIP_ASSERT("ret == dhcp->options_in_len", ret == dhcp->options_in_len);
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("dhcp_unfold_reply(): copied %"U16_F" bytes to dhcp->options_in[]\n",
      dhcp->options_in_len));
  }
  LWIP_UNUSED_ARG(ret);
  return ERR_OK;
}

/**
 * Free the incoming DHCP message including contiguous copy of
 * its DHCP options.
 *
 */
static void dhcp_free_reply(struct dhcp *dhcp)
{
  if (dhcp->msg_in != NULL) {
    mem_free((void *)dhcp->msg_in);
    dhcp->msg_in = NULL;
  }
  if (dhcp->options_in) {
    mem_free((void *)dhcp->options_in);
    dhcp->options_in = NULL;
    dhcp->options_in_len = 0;
  }
  LWIP_DEBUGF(DHCP_DEBUG, ("dhcp_free_reply(): free'd\n"));
}


/**
 * If an incoming DHCP message is in response to us, then trigger the state machine
 */
static void dhcp_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
{
  struct netif *netif = (struct netif *)arg;
  struct dhcp *dhcp = netif->dhcp;
  struct dhcp_msg *reply_msg = (struct dhcp_msg *)p->payload;
  u8_t *options_ptr;
  u8_t msg_type;
  u8_t i;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 3, ("dhcp_recv(pbuf = %p) from DHCP server %"U16_F".%"U16_F".%"U16_F".%"U16_F" port %"U16_F"\n", (void*)p,
    (u16_t)(ntohl(addr->addr) >> 24 & 0xff), (u16_t)(ntohl(addr->addr) >> 16 & 0xff),
    (u16_t)(ntohl(addr->addr) >>  8 & 0xff), (u16_t)(ntohl(addr->addr) & 0xff), port));
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("pbuf->len = %"U16_F"\n", p->len));
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("pbuf->tot_len = %"U16_F"\n", p->tot_len));
  /* prevent warnings about unused arguments */
  LWIP_UNUSED_ARG(pcb);
  LWIP_UNUSED_ARG(addr);
  LWIP_UNUSED_ARG(port);
  dhcp->p = p;
  /* TODO: check packet length before reading them */
  if (reply_msg->op != DHCP_BOOTREPLY) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("not a DHCP reply message, but type %"U16_F"\n", (u16_t)reply_msg->op));
    goto free_pbuf_and_return;
  }
  /* iterate through hardware address and match against DHCP message */
  for (i = 0; i < netif->hwaddr_len; i++) {
    if (netif->hwaddr[i] != reply_msg->chaddr[i]) {
      LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("netif->hwaddr[%"U16_F"]==%02"X16_F" != reply_msg->chaddr[%"U16_F"]==%02"X16_F"\n",
        (u16_t)i, (u16_t)netif->hwaddr[i], (u16_t)i, (u16_t)reply_msg->chaddr[i]));
      goto free_pbuf_and_return;
    }
  }
  /* match transaction ID against what we expected */
  if (ntohl(reply_msg->xid) != dhcp->xid) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("transaction id mismatch reply_msg->xid(%"X32_F")!=dhcp->xid(%"X32_F")\n",ntohl(reply_msg->xid),dhcp->xid));
    goto free_pbuf_and_return;
  }
  /* option fields could be unfold? */
  if (dhcp_unfold_reply(dhcp) != ERR_OK) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("problem unfolding DHCP message - too short on memory?\n"));
    goto free_pbuf_and_return;
  }

  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("searching DHCP_OPTION_MESSAGE_TYPE\n"));
  /* obtain pointer to DHCP message type */
  options_ptr = dhcp_get_option_ptr(dhcp, DHCP_OPTION_MESSAGE_TYPE);
  if (options_ptr == NULL) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("DHCP_OPTION_MESSAGE_TYPE option not found\n"));
    goto free_pbuf_and_return;
  }

  /* read DHCP message type */
  msg_type = dhcp_get_option_byte(options_ptr + 2);
  /* message type is DHCP ACK? */
  if (msg_type == DHCP_ACK) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("DHCP_ACK received\n"));
    /* in requesting state? */
    if (dhcp->state == DHCP_REQUESTING) {
      dhcp_handle_ack(netif);
      dhcp->request_timeout = 0;
#if DHCP_DOES_ARP_CHECK
      /* check if the acknowledged lease address is already in use */
      dhcp_check(netif);
#else
      /* bind interface to the acknowledged lease address */
      dhcp_bind(netif);
#endif
    }
    /* already bound to the given lease address? */
    else if ((dhcp->state == DHCP_REBOOTING) || (dhcp->state == DHCP_REBINDING) || (dhcp->state == DHCP_RENEWING)) {
      dhcp->request_timeout = 0;
      dhcp_bind(netif);
    }
  }
  /* received a DHCP_NAK in appropriate state? */
  else if ((msg_type == DHCP_NAK) &&
    ((dhcp->state == DHCP_REBOOTING) || (dhcp->state == DHCP_REQUESTING) ||
     (dhcp->state == DHCP_REBINDING) || (dhcp->state == DHCP_RENEWING  ))) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("DHCP_NAK received\n"));
    dhcp->request_timeout = 0;
    dhcp_handle_nak(netif);
  }
  /* received a DHCP_OFFER in DHCP_SELECTING state? */
  else if ((msg_type == DHCP_OFFER) && (dhcp->state == DHCP_SELECTING)) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("DHCP_OFFER received in DHCP_SELECTING state\n"));
    dhcp->request_timeout = 0;
    /* remember offered lease */
    dhcp_handle_offer(netif);
  }
free_pbuf_and_return:
  dhcp_free_reply(dhcp);
  pbuf_free(p);
  dhcp->p = NULL;
}

/**
 * Create a DHCP request, fill in common headers
 *
 * @param netif the netif under DHCP control
 */
static err_t
dhcp_create_request(struct netif *netif)
{
  struct dhcp *dhcp;
  u16_t i;
#ifndef DHCP_GLOBAL_XID
  /** default global transaction identifier starting value (easy to match
   *  with a packet analyser). We simply increment for each new request.
   *  Predefine DHCP_GLOBAL_XID to a better value or a function call to generate one
   *  at runtime, any supporting function prototypes can be defined in DHCP_GLOBAL_XID_HEADER */
  static u32_t xid = 0xABCD0000;
#else
  static u32_t xid;
  static u8_t xid_initialised = 0;
  if (!xid_initialised) {
    xid = DHCP_GLOBAL_XID;
    xid_initialised = !xid_initialised;
  }
#endif
  LWIP_ERROR("dhcp_create_request: netif != NULL", (netif != NULL), return ERR_ARG;);
  dhcp = netif->dhcp;
  LWIP_ERROR("dhcp_create_request: dhcp != NULL", (dhcp != NULL), return ERR_VAL;);
  LWIP_ASSERT("dhcp_create_request: dhcp->p_out == NULL", dhcp->p_out == NULL);
  LWIP_ASSERT("dhcp_create_request: dhcp->msg_out == NULL", dhcp->msg_out == NULL);
  dhcp->p_out = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dhcp_msg), PBUF_RAM);
  if (dhcp->p_out == NULL) {
    LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("dhcp_create_request(): could not allocate pbuf\n"));
    return ERR_MEM;
  }
  LWIP_ASSERT("dhcp_create_request: check that first pbuf can hold struct dhcp_msg",
           (dhcp->p_out->len >= sizeof(struct dhcp_msg)));

  /* reuse transaction identifier in retransmissions */
  if (dhcp->tries==0)
      xid++;
  dhcp->xid = xid;
  LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2,
              ("transaction id xid(%"X32_F")\n", xid));

  dhcp->msg_out = (struct dhcp_msg *)dhcp->p_out->payload;

  dhcp->msg_out->op = DHCP_BOOTREQUEST;
  /* TODO: make link layer independent */
  dhcp->msg_out->htype = DHCP_HTYPE_ETH;
  /* TODO: make link layer independent */
  dhcp->msg_out->hlen = DHCP_HLEN_ETH;
  dhcp->msg_out->hops = 0;
  dhcp->msg_out->xid = htonl(dhcp->xid);
  dhcp->msg_out->secs = 0;
  dhcp->msg_out->flags = 0;
  dhcp->msg_out->ciaddr.addr = 0;
  if (dhcp->state==DHCP_BOUND || dhcp->state==DHCP_RENEWING || dhcp->state==DHCP_REBINDING) {
    dhcp->msg_out->ciaddr.addr = netif->ip_addr.addr;
  }
  dhcp->msg_out->yiaddr.addr = 0;
  dhcp->msg_out->siaddr.addr = 0;
  dhcp->msg_out->giaddr.addr = 0;
  for (i = 0; i < DHCP_CHADDR_LEN; i++) {
    /* copy netif hardware address, pad with zeroes */
    dhcp->msg_out->chaddr[i] = (i < netif->hwaddr_len) ? netif->hwaddr[i] : 0/* pad byte*/;
  }
  for (i = 0; i < DHCP_SNAME_LEN; i++) {
    dhcp->msg_out->sname[i] = 0;
  }
  for (i = 0; i < DHCP_FILE_LEN; i++) {
    dhcp->msg_out->file[i] = 0;
  }
  dhcp->msg_out->cookie = htonl(0x63825363UL);
  dhcp->options_out_len = 0;
  /* fill options field with an incrementing array (for debugging purposes) */
  for (i = 0; i < DHCP_OPTIONS_LEN; i++) {
    dhcp->msg_out->options[i] = (u8_t)i; /* for debugging only, no matter if truncated */
  }
  return ERR_OK;
}

/**
 * Free previously allocated memory used to send a DHCP request.
 *
 * @param netif the netif under DHCP control
 */
static void
dhcp_delete_request(struct netif *netif)
{
  struct dhcp *dhcp;
  LWIP_ERROR("dhcp_delete_request: netif != NULL", (netif != NULL), return;);
  dhcp = netif->dhcp;
  LWIP_ERROR("dhcp_delete_request: dhcp != NULL", (dhcp != NULL), return;);
  LWIP_ASSERT("dhcp_delete_request: dhcp->p_out != NULL", dhcp->p_out != NULL);
  LWIP_ASSERT("dhcp_delete_request: dhcp->msg_out != NULL", dhcp->msg_out != NULL);
  if (dhcp->p_out != NULL) {
    pbuf_free(dhcp->p_out);
  }
  dhcp->p_out = NULL;
  dhcp->msg_out = NULL;
}

/**
 * Add a DHCP message trailer
 *
 * Adds the END option to the DHCP message, and if
 * necessary, up to three padding bytes.
 *
 * @param dhcp DHCP state structure
 */
static void
dhcp_option_trailer(struct dhcp *dhcp)
{
  LWIP_ERROR("dhcp_option_trailer: dhcp != NULL", (dhcp != NULL), return;);
  LWIP_ASSERT("dhcp_option_trailer: dhcp->msg_out != NULL\n", dhcp->msg_out != NULL);
  LWIP_ASSERT("dhcp_option_trailer: dhcp->options_out_len < DHCP_OPTIONS_LEN\n", dhcp->options_out_len < DHCP_OPTIONS_LEN);
  dhcp->msg_out->options[dhcp->options_out_len++] = DHCP_OPTION_END;
  /* packet is too small, or not 4 byte aligned? */
  while ((dhcp->options_out_len < DHCP_MIN_OPTIONS_LEN) || (dhcp->options_out_len & 3)) {
    /* LWIP_DEBUGF(DHCP_DEBUG,("dhcp_option_trailer:dhcp->options_out_len=%"U16_F", DHCP_OPTIONS_LEN=%"U16_F, dhcp->options_out_len, DHCP_OPTIONS_LEN)); */
    LWIP_ASSERT("dhcp_option_trailer: dhcp->options_out_len < DHCP_OPTIONS_LEN\n", dhcp->options_out_len < DHCP_OPTIONS_LEN);
    /* add a fill/padding byte */
    dhcp->msg_out->options[dhcp->options_out_len++] = 0;
  }
}

/**
 * Find the offset of a DHCP option inside the DHCP message.
 *
 * @param dhcp DHCP client
 * @param option_type
 *
 * @return a byte offset into the UDP message where the option was found, or
 * zero if the given option was not found.
 */
static u8_t *dhcp_get_option_ptr(struct dhcp *dhcp, u8_t option_type)
{
  u8_t overload = DHCP_OVERLOAD_NONE;

  /* options available? */
  if ((dhcp->options_in != NULL) && (dhcp->options_in_len > 0)) {
    /* start with options field */
    u8_t *options = (u8_t *)dhcp->options_in;
    u16_t offset = 0;
    /* at least 1 byte to read and no end marker, then at least 3 bytes to read? */
    while ((offset < dhcp->options_in_len) && (options[offset] != DHCP_OPTION_END)) {
      /* LWIP_DEBUGF(DHCP_DEBUG, ("msg_offset=%"U16_F", q->len=%"U16_F, msg_offset, q->len)); */
      /* are the sname and/or file field overloaded with options? */
      if (options[offset] == DHCP_OPTION_OVERLOAD) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 2, ("overloaded message detected\n"));
        /* skip option type and length */
        offset += 2;
        overload = options[offset++];
      }
      /* requested option found */
      else if (options[offset] == option_type) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("option found at offset %"U16_F" in options\n", offset));
        return &options[offset];
      /* skip option */
      } else {
         LWIP_DEBUGF(DHCP_DEBUG, ("skipping option %"U16_F" in options\n", options[offset]));
        /* skip option type */
        offset++;
        /* skip option length, and then length bytes */
        offset += 1 + options[offset];
      }
    }
    /* is this an overloaded message? */
    if (overload != DHCP_OVERLOAD_NONE) {
      u16_t field_len;
      if (overload == DHCP_OVERLOAD_FILE) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("overloaded file field\n"));
        options = (u8_t *)&dhcp->msg_in->file;
        field_len = DHCP_FILE_LEN;
      } else if (overload == DHCP_OVERLOAD_SNAME) {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("overloaded sname field\n"));
        options = (u8_t *)&dhcp->msg_in->sname;
        field_len = DHCP_SNAME_LEN;
      /* TODO: check if else if () is necessary */
      } else {
        LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | 1, ("overloaded sname and file field\n"));
        options = (u8_t *)&dhcp->msg_in->sname;
        field_len = DHCP_FILE_LEN + DHCP_SNAME_LEN;
      }
      offset = 0;

      /* at least 1 byte to read and no end marker */
      while ((offset < field_len) && (options[offset] != DHCP_OPTION_END)) {
        if (options[offset] == option_type) {
           LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("option found at offset=%"U16_F"\n", offset));
          return &options[offset];
        /* skip option */
        } else {
          LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE, ("skipping option %"U16_F"\n", options[offset]));
          /* skip option type */
          offset++;
          offset += 1 + options[offset];
        }
      }
    }
  }
  return NULL;
}

/**
 * Return the byte of DHCP option data.
 *
 * @param client DHCP client.
 * @param ptr pointer obtained by dhcp_get_option_ptr().
 *
 * @return byte value at the given address.
 */
static u8_t
dhcp_get_option_byte(u8_t *ptr)
{
  LWIP_DEBUGF(DHCP_DEBUG, ("option byte value=%"U16_F"\n", (u16_t)(*ptr)));
  return *ptr;
}

#if 0 /* currently unused */
/**
 * Return the 16-bit value of DHCP option data.
 *
 * @param client DHCP client.
 * @param ptr pointer obtained by dhcp_get_option_ptr().
 *
 * @return byte value at the given address.
 */
static u16_t
dhcp_get_option_short(u8_t *ptr)
{
  u16_t value;
  value = *ptr++ << 8;
  value |= *ptr;
  LWIP_DEBUGF(DHCP_DEBUG, ("option short value=%"U16_F"\n", value));
  return value;
}
#endif

/**
 * Return the 32-bit value of DHCP option data.
 *
 * @param client DHCP client.
 * @param ptr pointer obtained by dhcp_get_option_ptr().
 *
 * @return byte value at the given address.
 */
static u32_t dhcp_get_option_long(u8_t *ptr)
{
  u32_t value;
  value = (u32_t)(*ptr++) << 24;
  value |= (u32_t)(*ptr++) << 16;
  value |= (u32_t)(*ptr++) << 8;
  value |= (u32_t)(*ptr++);
  LWIP_DEBUGF(DHCP_DEBUG, ("option long value=%"U32_F"\n", value));
  return value;
}

#endif /* LWIP_DHCP */