Projects/Webserver/Lib/DHCPServerApp.c

   1 /*
   2              LUFA Library
   3      Copyright (C) Dean Camera, 2011.
   4
   5   dean [at] fourwalledcubicle [dot] com
   6            www.lufa-lib.org
   7 */
   8
   9 /*
  10   Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)
  11
  12   Permission to use, copy, modify, distribute, and sell this
  13   software and its documentation for any purpose is hereby granted
  14   without fee, provided that the above copyright notice appear in
  15   all copies and that both that the copyright notice and this
  16   permission notice and warranty disclaimer appear in supporting
  17   documentation, and that the name of the author not be used in
  18   advertising or publicity pertaining to distribution of the
  19   software without specific, written prior permission.
  20
  21   The author disclaim all warranties with regard to this
  22   software, including all implied warranties of merchantability
  23   and fitness.  In no event shall the author be liable for any
  24   special, indirect or consequential damages or any damages
  25   whatsoever resulting from loss of use, data or profits, whether
  26   in an action of contract, negligence or other tortious action,
  27   arising out of or in connection with the use or performance of
  28   this software.
  29 */
  30
  31 #if defined(ENABLE_DHCP_SERVER) || defined(__DOXYGEN__)
  32
  33 /** \file
  34  *
  35  *  DHCP Server Application. When connected to the uIP stack, this will send IP configuration settings to a
  36  *  DHCP client on the network.
  37  */
  38
  39 #define  INCLUDE_FROM_DHCPSERVERAPP_C
  40 #include "DHCPServerApp.h"
  41
  42 struct uip_conn* BroadcastConnection;
  43
  44 uint8_t LeasedIPs[255 / 8];
  45
  46 /** Initialization function for the DHCP server. */
  47 void DHCPServerApp_Init(void)
  48 {
  49         /* Listen on port 67 for DHCP server connections from hosts */
  50         uip_listen(HTONS(DHCP_SERVER_PORT));
  51
  52         /* Create a new UDP connection to the DHCP server port for the DHCP solicitation */
  53         struct uip_udp_conn* BroadcastConnection = uip_udp_new(&uip_broadcast_addr, HTONS(DHCP_CLIENT_PORT));
  54
  55         /* If the connection was successfully created, bind it to the local DHCP client port */
  56         if (BroadcastConnection != NULL)
  57           uip_udp_bind(BroadcastConnection, HTONS(DHCP_SERVER_PORT));
  58
  59         /* Set all IP addresses as unleased */
  60         memset(LeasedIPs, 0x00, sizeof(LeasedIPs));
  61 }
  62
  63 /** uIP stack application callback for the DHCP server. This function must be called each time the TCP/IP stack
  64  *  needs a UDP packet to be processed.
  65  */
  66 void DHCPServerApp_Callback(void)
  67 {
  68         DHCP_Header_t* const AppData     = (DHCP_Header_t*)uip_appdata;
  69         uint16_t             AppDataSize = 0;
  70
  71         /* Only process when new data arrives - don't retransmit lost packets */
  72         if (uip_newdata())
  73         {
  74                 /* Get the DHCP message type (if present), otherwise early-abort */
  75                 uint8_t DHCPMessageType;
  76                 if (!(DHCPCommon_GetOption(AppData->Options, DHCP_OPTION_MSG_TYPE, &DHCPMessageType)))
  77                         return;
  78
  79                 uip_ipaddr_t        Netmask, GatewayIPAddress, PreferredClientIP;
  80                 struct uip_eth_addr RemoteMACAddress;
  81                 uint32_t            TransactionID;
  82
  83                 /* Get configured network mask, gateway IP and extract out DHCP transaction ID and remote IP */
  84                 uip_getnetmask(&Netmask);
  85                 uip_getdraddr(&GatewayIPAddress);
  86                 memcpy(&RemoteMACAddress, &AppData->ClientHardwareAddress, sizeof(struct uip_eth_addr));
  87                 TransactionID = AppData->TransactionID;
  88
  89                 /* Try to extract out the client's preferred IP address if it is indicated in the packet */
  90                 if (!(DHCPCommon_GetOption(AppData->Options, DHCP_OPTION_REQ_IPADDR, &PreferredClientIP)))
  91                   memcpy(&PreferredClientIP, &uip_all_zeroes_addr, sizeof(uip_ipaddr_t));
  92
  93                 switch (DHCPMessageType)
  94                 {
  95                         case DHCP_DISCOVER:
  96                                 /* If no preference was made or the preferred IP is already taken, find a new address */
  97                                 if (DHCPServerApp_CheckIfIPLeased(&PreferredClientIP))
  98                                   DHCPServerApp_GetUnleasedIP(&PreferredClientIP);
  99
 100                                 /* Create a new DHCP OFFER packet with the offered IP address */
 101                                 AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_OFFER, &RemoteMACAddress, &PreferredClientIP, TransactionID);
 102
 103                                 /* Add network mask and router information to the list of DHCP OFFER packet options */
 104                                 AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_SUBNET_MASK,
 105                                                                                                         sizeof(uip_ipaddr_t), &Netmask);
 106                                 AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_ROUTER,
 107                                                                         sizeof(uip_ipaddr_t), &GatewayIPAddress);
 108
 109                                 /* Send the DHCP OFFER packet */
 110                                 uip_poll_conn(BroadcastConnection);
 111                                 memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));
 112                                 uip_udp_send(AppDataSize);
 113
 114                                 break;
 115                         case DHCP_REQUEST:
 116                                 /* Check to see if the requested IP address has already been leased to a client */
 117                                 if (!(DHCPServerApp_CheckIfIPLeased(&PreferredClientIP)))
 118                                 {
 119                                         /* Create a new DHCP ACK packet to accept the IP address lease */
 120                                         AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_ACK, &RemoteMACAddress, &PreferredClientIP, TransactionID);
 121
 122                                         /* Add network mask and router information to the list of DHCP ACK packet options */
 123                                         AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_SUBNET_MASK,
 124                                                                                                                 sizeof(uip_ipaddr_t), &Netmask);
 125                                         AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_ROUTER,
 126                                                                             sizeof(uip_ipaddr_t), &GatewayIPAddress);
 127
 128                                         /* Mark the requested IP as leased to a client */
 129                                         DHCPServerApp_LeaseIP(&PreferredClientIP);
 130                                 }
 131                                 else
 132                                 {
 133                                         /* Create a new DHCP NAK packet to reject the requested allocation */
 134                                         AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_NAK, &RemoteMACAddress, &uip_all_zeroes_addr, TransactionID);
 135                                 }
 136
 137                                 /* Send the DHCP ACK or NAK packet */
 138                                 uip_poll_conn(BroadcastConnection);
 139                                 memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));
 140                                 uip_udp_send(AppDataSize);
 141
 142                                 break;
 143                         case DHCP_RELEASE:
 144                                 /* Mark the IP address as released in the allocation table */
 145                                 DHCPServerApp_UnleaseIP(&uip_udp_conn->ripaddr);
 146                                 break;
 147                 }
 148         }
 149 }
 150
 151 /** Fills the DHCP packet response with the appropriate BOOTP header for DHCP. This fills out all the required
 152  *  fields, leaving only the additional DHCP options to be added to the packet before it is sent to the DHCP client.
 153  *
 154  *  \param[out] DHCPHeader             Location in the packet buffer where the BOOTP header should be written to
 155  *  \param[in]  DHCPMessageType        DHCP Message type, such as DHCP_DISCOVER
 156  *  \param[in]  ClientHardwareAddress  Client MAC address the created transaction should be directed to
 157  *  \param[in]  PreferredClientIP      Preferred IP that should be given to the client if it is unallocated
 158  *  \param[in]  TransactionID          Transaction ID the created transaction should be associated with
 159  *
 160  *  \return Size in bytes of the created DHCP packet
 161  */
 162 static uint16_t DHCPServerApp_FillDHCPHeader(DHCP_Header_t* const DHCPHeader,
 163                                              const uint8_t DHCPMessageType,
 164                                              const struct uip_eth_addr* const ClientHardwareAddress,
 165                                                                                          const uip_ipaddr_t* const PreferredClientIP,
 166                                              const uint32_t TransactionID)
 167 {
 168         /* Erase existing packet data so that we start will all 0x00 DHCP header data */
 169         memset(DHCPHeader, 0, sizeof(DHCP_Header_t));
 170
 171         DHCPHeader->Operation             = DHCPMessageType;
 172         DHCPHeader->HardwareType          = DHCP_HTYPE_ETHERNET;
 173         DHCPHeader->HardwareAddressLength = sizeof(MACAddress);
 174         DHCPHeader->Hops                  = 0;
 175         DHCPHeader->TransactionID         = TransactionID;
 176         DHCPHeader->ElapsedSeconds        = 0;
 177         DHCPHeader->Flags                 = 0;
 178         memcpy(&DHCPHeader->NextServerIP, &uip_hostaddr, sizeof(uip_ipaddr_t));
 179         memcpy(&DHCPHeader->YourIP, PreferredClientIP, sizeof(uip_ipaddr_t));
 180         memcpy(&DHCPHeader->ClientHardwareAddress, ClientHardwareAddress, sizeof(struct uip_eth_addr));
 181         DHCPHeader->Cookie                = DHCP_MAGIC_COOKIE;
 182
 183         /* Add a DHCP message type and terminator options to the start of the DHCP options field */
 184         DHCPHeader->Options[0]            = DHCP_OPTION_MSG_TYPE;
 185         DHCPHeader->Options[1]            = 1;
 186         DHCPHeader->Options[2]            = DHCPMessageType;
 187         DHCPHeader->Options[3]            = DHCP_OPTION_END;
 188
 189         /* Calculate the total number of bytes added to the outgoing packet */
 190         return (sizeof(DHCP_Header_t) + 4);
 191 }
 192
 193 /** Checks to see if the nominated IP address has already been allocated to a client.
 194  *
 195  *  \param[in] IPAddress  IP Address whose lease status should be checked
 196  *
 197  *  \pre The IP address must be within the same /24 subnet as the virtual webserver.
 198  *
 199  *  \return Boolean true if the IP has already been leased to a client, false otherwise.
 200  */
 201 static bool DHCPServerApp_CheckIfIPLeased(const uip_ipaddr_t* const IPAddress)
 202 {
 203         uint8_t Byte = (IPAddress->u8[3] / 8);
 204         uint8_t Mask = (1 << (IPAddress->u8[3] % 8));
 205
 206         /* Make sure that the requested IP address isn't already leased to the virtual server or another client */
 207         if (IPAddress->u8[3] && !(IPAddress->u8[3] == uip_hostaddr.u8[3]) && !(LeasedIPs[Byte] & Mask))
 208           return false;
 209         else
 210           return true;
 211 }
 212
 213 /** Retrieves the next unleased IP in the IP address pool.
 214  *
 215  *  \param[out] NewIPAddress  Location where the generated IP Address should be stored
 216  */
 217 static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* const NewIPAddress)
 218 {
 219         uip_ipaddr_copy(NewIPAddress, &uip_hostaddr);
 220
 221         /** Look through the current subnet, skipping the broadcast and zero IP addresses */
 222         for (uint8_t IP = 1; IP < 254; IP++)
 223         {
 224                 /* Update new IP address to lease with the current IP address to test */
 225                 NewIPAddress->u8[3] = IP;
 226
 227                 /* If we've found an unleased IP, abort with the updated IP stored for the called */
 228                 if (!(DHCPServerApp_CheckIfIPLeased(NewIPAddress)))
 229                   return;
 230         }
 231 }
 232
 233 /** Marks the given IP Address as leased in the address pool, so that it will not be
 234  *  allocated to another client unless it is first released.
 235  *
 236  *  \param[in] IPAddress  IP Address to mark as leased
 237  *
 238  *  \pre The IP address must be within the same /24 subnet as the virtual webserver.
 239  */
 240 static void DHCPServerApp_LeaseIP(const uip_ipaddr_t* const IPAddress)
 241 {
 242         uint8_t Byte = (IPAddress->u8[3] / 8);
 243         uint8_t Mask = (1 << (IPAddress->u8[3] % 8));
 244
 245         /* Mark the IP address as leased in the allocation table */
 246         LeasedIPs[Byte] |= Mask;
 247 }
 248
 249 /** Marks the given IP Address as not leased in the address pool, so that it can be
 250  *  allocated to another client upon request.
 251  *
 252  *  \param[in] IPAddress  IP Address to mark as not leased
 253  *
 254  *  \pre The IP address must be within the same /24 subnet as the virtual webserver.
 255  */
 256 static void DHCPServerApp_UnleaseIP(const uip_ipaddr_t* const IPAddress)
 257 {
 258         uint8_t Byte = (IPAddress->u8[3] / 8);
 259         uint8_t Mask = (1 << (IPAddress->u8[3] % 8));
 260
 261         /* Mark the IP address as unleased in the allocation table */
 262         LeasedIPs[Byte] &= ~Mask;
 263 }
 264 #endif
 265