Correct errors in the DHCP Server application in the Webserver project, that was causing random server restarts and/or incorrectly allocated IP addresses.

2 files changed, 90 insertions, 62 deletions

diff --git a/Projects/Webserver/Lib/DHCPServerApp.c b/Projects/Webserver/Lib/DHCPServerApp.c
index 84c57d0a2..7a36066cb 100644
--- a/Projects/Webserver/Lib/DHCPServerApp.c
+++ b/Projects/Webserver/Lib/DHCPServerApp.c
@@ -68,62 +68,83 @@ void DHCPServerApp_Callback(void)
 	DHCP_Header_t* const AppData     = (DHCP_Header_t*)uip_appdata;

 	uint16_t             AppDataSize = 0;

 

-	uint8_t DHCPMessageType;

-	if (!(DHCPCommon_GetOption(AppData->Options, DHCP_OPTION_MSG_TYPE, &DHCPMessageType)))

-		return;

-

-	uip_ipaddr_t Netmask, GatewayIPAddress;

-	struct uip_eth_addr RemoteMACAddress;

-	uint32_t            TransactionID;

+	/* Only process when new data arrives - don't retransmit lost packets */

+	if (uip_newdata())

+	{

+		/* Get the DHCP message type (if present), otherwise early-abort */

+		uint8_t DHCPMessageType;

+		if (!(DHCPCommon_GetOption(AppData->Options, DHCP_OPTION_MSG_TYPE, &DHCPMessageType)))

+			return;

 

-	memcpy(&RemoteMACAddress, &AppData->ClientHardwareAddress, sizeof(struct uip_eth_addr));

-	uip_getnetmask(&Netmask);

-	uip_getdraddr(&GatewayIPAddress);	

-	TransactionID = AppData->TransactionID;

+		uip_ipaddr_t        Netmask, GatewayIPAddress, PreferredClientIP;

+		struct uip_eth_addr RemoteMACAddress;

+		uint32_t            TransactionID;

 

-	switch (DHCPMessageType)

-	{

-		case DHCP_DISCOVER:

-			AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_OFFER, &RemoteMACAddress, TransactionID);

+		/* Get configured network mask, gateway IP and extract out DHCP transaction ID and remote IP */

+		uip_getnetmask(&Netmask);

+		uip_getdraddr(&GatewayIPAddress);

+		memcpy(&RemoteMACAddress, &AppData->ClientHardwareAddress, sizeof(struct uip_eth_addr));

+		TransactionID = AppData->TransactionID;

 

-			AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_SUBNET_MASK,

-			                                    sizeof(uip_ipaddr_t), &Netmask);

-			AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_ROUTER,

-			                                    sizeof(uip_ipaddr_t), &GatewayIPAddress);

-			

-			/* Send the DHCP OFFER packet */

-			uip_poll_conn(BroadcastConnection);

-			memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));

-			uip_udp_send(AppDataSize);

+		/* Try to extract out the client's preferred IP address if it is indicated in the packet */

+		if (!(DHCPCommon_GetOption(AppData->Options, DHCP_OPTION_REQ_IPADDR, &PreferredClientIP)))

+		  memcpy(&PreferredClientIP, &uip_all_zeroes_addr, sizeof(uip_ipaddr_t));	

+		

+		switch (DHCPMessageType)

+		{

+			case DHCP_DISCOVER:

+				/* If no preference was made or the preferred IP is already taken, find a new address */

+				if (DHCPServerApp_CheckIfIPLeased(&PreferredClientIP))

+				  DHCPServerApp_GetUnleasedIP(&PreferredClientIP);

 

-			break;

-		case DHCP_REQUEST:

-			if (!(DHCPServerApp_CheckIfIPLeased(&AppData->YourIP)))

-			{

-				AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_ACK, &RemoteMACAddress, TransactionID);

+				/* Create a new DHCP OFFER packet with the offered IP address */

+				AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_OFFER, &RemoteMACAddress, &PreferredClientIP, TransactionID);

 

+				/* Add network mask and router information to the list of DHCP OFFER packet options */

 				AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_SUBNET_MASK,

 													sizeof(uip_ipaddr_t), &Netmask);

 				AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_ROUTER,

-													sizeof(uip_ipaddr_t), &GatewayIPAddress);

-

-				DHCPServerApp_LeaseIP(&AppData->YourIP);

-			}

-			else

-			{

-				AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_NAK, &RemoteMACAddress, TransactionID);			

-			}

+					                                sizeof(uip_ipaddr_t), &GatewayIPAddress);

+

+				/* Send the DHCP OFFER packet */

+				uip_poll_conn(BroadcastConnection);

+				memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));

+				uip_udp_send(AppDataSize);

+

+				break;

+			case DHCP_REQUEST:

+				/* Check to see if the requested IP address has already been leased to a client */

+				if (!(DHCPServerApp_CheckIfIPLeased(&PreferredClientIP)))

+				{

+					/* Create a new DHCP ACK packet to accept the IP address lease */					

+					AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_ACK, &RemoteMACAddress, &PreferredClientIP, TransactionID);

+

+					/* Add network mask and router information to the list of DHCP ACK packet options */

+					AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_SUBNET_MASK,

+														sizeof(uip_ipaddr_t), &Netmask);

+					AppDataSize += DHCPCommon_SetOption(AppData->Options, DHCP_OPTION_ROUTER,

+					                                    sizeof(uip_ipaddr_t), &GatewayIPAddress);

+

+					/* Mark the requested IP as leased to a client */

+					DHCPServerApp_LeaseIP(&PreferredClientIP);

+				}

+				else

+				{

+					/* Create a new DHCP NAK packet to reject the requested allocation */

+					AppDataSize += DHCPServerApp_FillDHCPHeader(AppData, DHCP_NAK, &RemoteMACAddress, &uip_all_zeroes_addr, TransactionID);

+				}

+				

+				/* Send the DHCP ACK or NAK packet */

+				uip_poll_conn(BroadcastConnection);

+				memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));

+				uip_udp_send(AppDataSize);

 			

-			/* Send the DHCP ACK or NAK packet */

-			uip_poll_conn(BroadcastConnection);

-			memcpy(&uip_udp_conn->ripaddr, &uip_broadcast_addr, sizeof(uip_ipaddr_t));

-			uip_udp_send(AppDataSize);

-		

-			break;

-		case DHCP_RELEASE:

-			/* Mark the IP address as released in the allocation table */

-			DHCPServerApp_UnleaseIP(&uip_udp_conn->ripaddr);

-			break;

+				break;

+			case DHCP_RELEASE:

+				/* Mark the IP address as released in the allocation table */

+				DHCPServerApp_UnleaseIP(&uip_udp_conn->ripaddr);

+				break;

+		}

 	}

 }

 

@@ -139,8 +160,9 @@ void DHCPServerApp_Callback(void)
  */

 static uint16_t DHCPServerApp_FillDHCPHeader(DHCP_Header_t* const DHCPHeader,

                                              const uint8_t DHCPMessageType,

-                                             struct uip_eth_addr* ClientHardwareAddress,

-                                             uint32_t TransactionID)

+                                             const struct uip_eth_addr* const ClientHardwareAddress,

+											 const uip_ipaddr_t* const PreferredClientIP,

+                                             const uint32_t TransactionID)

 {

 	/* Erase existing packet data so that we start will all 0x00 DHCP header data */

  	memset(DHCPHeader, 0, sizeof(DHCP_Header_t));

@@ -153,8 +175,7 @@ static uint16_t DHCPServerApp_FillDHCPHeader(DHCP_Header_t* const DHCPHeader,
 	DHCPHeader->ElapsedSeconds        = 0;

 	DHCPHeader->Flags                 = 0;

 	memcpy(&DHCPHeader->NextServerIP, &uip_hostaddr, sizeof(uip_ipaddr_t));

-	if (uip_ipaddr_cmp(&DHCPHeader->YourIP, &uip_all_zeroes_addr))

-	  DHCPServerApp_GetUnleasedIP(&DHCPHeader->YourIP);

+	memcpy(&DHCPHeader->YourIP, PreferredClientIP, sizeof(uip_ipaddr_t));

 	memcpy(&DHCPHeader->ClientHardwareAddress, ClientHardwareAddress, sizeof(struct uip_eth_addr));

 	DHCPHeader->Cookie                = DHCP_MAGIC_COOKIE;

 	  

@@ -176,12 +197,13 @@ static uint16_t DHCPServerApp_FillDHCPHeader(DHCP_Header_t* const DHCPHeader,
  *

  *  \return Boolean true if the IP has already been leased to a client, false otherwise.

  */

-static bool DHCPServerApp_CheckIfIPLeased(uip_ipaddr_t* IPAddress)

+static bool DHCPServerApp_CheckIfIPLeased(const uip_ipaddr_t* const IPAddress)

 {

 	uint8_t Byte = (IPAddress->u8[3] / 8);

 	uint8_t Mask = (1 << (IPAddress->u8[3] % 8));

 	

-	if (!(IPAddress->u8[3] == uip_hostaddr.u8[3]) && !(LeasedIPs[Byte] & Mask))

+	/* Make sure that the requested IP address isn't already leased to the virtual server or another client */

+	if (IPAddress->u8[3] && !(IPAddress->u8[3] == uip_hostaddr.u8[3]) && !(LeasedIPs[Byte] & Mask))

 	  return false;

 	else

 	  return true;

@@ -191,14 +213,17 @@ static bool DHCPServerApp_CheckIfIPLeased(uip_ipaddr_t* IPAddress)
  *

  *  \param[out] NewIPAddress  Location where the generated IP Address should be stored

  */

-static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* NewIPAddress)

+static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* const NewIPAddress)

 {

 	uip_ipaddr_copy(NewIPAddress, &uip_hostaddr);

 	

+	/** Look through the current subnet, skipping the broadcast and zero IP addresses */

 	for (uint8_t IP = 1; IP < 254; IP++)

 	{

+		/* Update new IP address to lease with the current IP address to test */

 		NewIPAddress->u8[3] = IP;

 		

+		/* If we've found an unleased IP, abort with the updated IP stored for the called */

 		if (!(DHCPServerApp_CheckIfIPLeased(NewIPAddress)))

 		  return;

 	}

@@ -211,11 +236,12 @@ static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* NewIPAddress)
  *

  *  \pre The IP address must be within the same /24 subnet as the virtual webserver.

  */

-static void DHCPServerApp_LeaseIP(uip_ipaddr_t* IPAddress)

+static void DHCPServerApp_LeaseIP(const uip_ipaddr_t* const IPAddress)

 {

 	uint8_t Byte = (IPAddress->u8[3] / 8);

 	uint8_t Mask = (1 << (IPAddress->u8[3] % 8));

 	

+	/* Mark the IP address as leased in the allocation table */

 	LeasedIPs[Byte] |= Mask;

 }

 

@@ -226,11 +252,12 @@ static void DHCPServerApp_LeaseIP(uip_ipaddr_t* IPAddress)
  *

  *  \pre The IP address must be within the same /24 subnet as the virtual webserver.

  */

-static void DHCPServerApp_UnleaseIP(uip_ipaddr_t* IPAddress)

+static void DHCPServerApp_UnleaseIP(const uip_ipaddr_t* const IPAddress)

 {

 	uint8_t Byte = (IPAddress->u8[3] / 8);

 	uint8_t Mask = (1 << (IPAddress->u8[3] % 8));

 	

+	/* Mark the IP address as unleased in the allocation table */

 	LeasedIPs[Byte] &= ~Mask;

 }

 #endif

diff --git a/Projects/Webserver/Lib/DHCPServerApp.h b/Projects/Webserver/Lib/DHCPServerApp.h
index e70869588..9d91d6be8 100644
--- a/Projects/Webserver/Lib/DHCPServerApp.h
+++ b/Projects/Webserver/Lib/DHCPServerApp.h
@@ -51,12 +51,13 @@
 		#if defined(INCLUDE_FROM_DHCPSERVERAPP_C)

 		static uint16_t DHCPServerApp_FillDHCPHeader(DHCP_Header_t* const DHCPHeader,

 		                                             const uint8_t DHCPMessageType,

-		                                             struct uip_eth_addr* ClientHardwareAddress,

-		                                             uint32_t TransactionID);

-		static bool DHCPServerApp_CheckIfIPLeased(uip_ipaddr_t* IPAddress);

-		static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* NewIPAddress);

-		static void DHCPServerApp_LeaseIP(uip_ipaddr_t* IPAddress);

-		static void DHCPServerApp_UnleaseIP(uip_ipaddr_t* IPAddress);

+		                                             const struct uip_eth_addr* const ClientHardwareAddress,

+		                                             const uip_ipaddr_t* const PreferredClientIP,

+		                                             const uint32_t TransactionID);

+		static bool DHCPServerApp_CheckIfIPLeased(const uip_ipaddr_t* const IPAddress);

+		static void DHCPServerApp_GetUnleasedIP(uip_ipaddr_t* const NewIPAddress);

+		static void DHCPServerApp_LeaseIP(const uip_ipaddr_t* const IPAddress);

+		static void DHCPServerApp_UnleaseIP(const uip_ipaddr_t* const IPAddress);

 		#endif

 #endif