Modules/IPStack/ipv4.c

   1 /*
   2  * Acess2 IP Stack
   3  * - IPv4 Protcol Handling
   4  */
   5 #include "ipstack.h"
   6 #include "link.h"
   7 #include "ipv4.h"
   8 #include "firewall.h"
   9
  10 #define DEFAULT_TTL     32
  11
  12 // === IMPORTS ===
  13 extern tInterface       *gIP_Interfaces;
  14 extern void     ICMP_Initialise();
  15 extern  int     ICMP_Ping(tInterface *Interface, tIPv4 Addr);
  16 extern tMacAddr ARP_Resolve4(tInterface *Interface, tIPv4 Address);
  17
  18 // === PROTOTYPES ===
  19  int    IPv4_Initialise();
  20  int    IPv4_RegisterCallback(int ID, tIPCallback Callback);
  21 void    IPv4_int_GetPacket(tAdapter *Interface, tMacAddr From, int Length, void *Buffer);
  22 tInterface      *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address, int Broadcast);
  23 Uint32  IPv4_Netmask(int FixedBits);
  24 Uint16  IPv4_Checksum(const void *Buf, int Size);
  25  int    IPv4_Ping(tInterface *Iface, tIPv4 Addr);
  26
  27 // === GLOBALS ===
  28 tIPCallback     gaIPv4_Callbacks[256];
  29
  30 // === CODE ===
  31 /**
  32  * \brief Initialise the IPv4 Code
  33  */
  34 int IPv4_Initialise()
  35 {
  36         ICMP_Initialise();
  37         Link_RegisterType(IPV4_ETHERNET_ID, IPv4_int_GetPacket);
  38         return 1;
  39 }
  40
  41 /**
  42  * \brief Registers a callback
  43  * \param ID    8-bit packet type ID
  44  * \param Callback      Callback function
  45  */
  46 int IPv4_RegisterCallback(int ID, tIPCallback Callback)
  47 {
  48         if( ID < 0 || ID > 255 )        return 0;
  49         if( gaIPv4_Callbacks[ID] )      return 0;
  50         gaIPv4_Callbacks[ID] = Callback;
  51         return 1;
  52 }
  53
  54 /**
  55  * \brief Creates and sends an IPv4 Packet
  56  * \param Iface Interface
  57  * \param Address       Destination IP
  58  * \param Protocol      Protocol ID
  59  * \param ID    Some random ID number
  60  * \param Length        Data Length
  61  * \param Data  Packet Data
  62  * \return Boolean Success
  63  */
  64 int IPv4_SendPacket(tInterface *Iface, tIPv4 Address, int Protocol, int ID, int Length, const void *Data)
  65 {
  66         tMacAddr        to = ARP_Resolve4(Iface, Address);
  67          int    bufSize = sizeof(tIPv4Header) + Length;
  68         char    buf[bufSize];
  69         tIPv4Header     *hdr = (void*)buf;
  70          int    ret;
  71
  72         // OUTPUT Firewall rule go here
  73         ret = IPTablesV4_TestChain("OUTPUT",
  74                 (tIPv4*)Iface->Address, &Address,
  75                 Protocol, 0,
  76                 Length, Data);
  77         if(ret != 0) {
  78                 // Just drop it (with an error)
  79                 return 0;
  80         }
  81
  82         memcpy(&hdr->Options[0], Data, Length);
  83         hdr->Version = 4;
  84         hdr->HeaderLength = sizeof(tIPv4Header)/4;
  85         hdr->DiffServices = 0;  // TODO: Check
  86
  87         hdr->Reserved = 0;
  88         hdr->DontFragment = 0;
  89         hdr->MoreFragments = 0;
  90         hdr->FragOffLow = 0;
  91         hdr->FragOffHi = 0;
  92
  93         hdr->TotalLength = htons( bufSize );
  94         hdr->Identifcation = htons( ID );       // TODO: Check
  95         hdr->TTL = DEFAULT_TTL;
  96         hdr->Protocol = Protocol;
  97         hdr->HeaderChecksum = 0;        // Will be set later
  98         hdr->Source = *(tIPv4*)Iface->Address;
  99         hdr->Destination = Address;
 100         hdr->HeaderChecksum = IPv4_Checksum(hdr, sizeof(tIPv4Header));
 101
 102         Log_Log("IPv4", "Sending packet to %i.%i.%i.%i",
 103                 Address.B[0], Address.B[1], Address.B[2], Address.B[3]);
 104         Link_SendPacket(Iface->Adapter, IPV4_ETHERNET_ID, to, bufSize, buf);
 105         return 1;
 106 }
 107
 108 /**
 109  * \fn void IPv4_int_GetPacket(tInterface *Adapter, tMacAddr From, int Length, void *Buffer)
 110  * \brief Process an IPv4 Packet
 111  */
 112 void IPv4_int_GetPacket(tAdapter *Adapter, tMacAddr From, int Length, void *Buffer)
 113 {
 114         tIPv4Header     *hdr = Buffer;
 115         tInterface      *iface;
 116         Uint8   *data;
 117          int    dataLength;
 118          int    ret;
 119
 120         if(Length < sizeof(tIPv4Header))        return;
 121
 122         #if 0
 123         //Log_Log("IPv4", "Version = %i", hdr->Version);
 124         //Log_Log("IPv4", "HeaderLength = %i", hdr->HeaderLength);
 125         //Log_Log("IPv4", "DiffServices = %i", hdr->DiffServices);
 126         Log_Debug("IPv4", "TotalLength = %i", ntohs(hdr->TotalLength) );
 127         //Log_Log("IPv4", "Identifcation = %i", ntohs(hdr->Identifcation) );
 128         //Log_Log("IPv4", "TTL = %i", hdr->TTL );
 129         Log_Debug("IPv4", "Protocol = %i", hdr->Protocol );
 130         //Log_Log("IPv4", "HeaderChecksum = 0x%x", ntohs(hdr->HeaderChecksum) );
 131         Log_Debug("IPv4", "Source = %i.%i.%i.%i",
 132                 hdr->Source.B[0], hdr->Source.B[1], hdr->Source.B[2], hdr->Source.B[3] );
 133         Log_Debug("IPv4", "Destination = %i.%i.%i.%i",
 134                 hdr->Destination.B[0], hdr->Destination.B[1],
 135                 hdr->Destination.B[2], hdr->Destination.B[3] );
 136         #endif
 137
 138         // Check that the version IS IPv4
 139         if(hdr->Version != 4) {
 140                 Log_Log("IPv4", "hdr->Version(%i) != 4", hdr->Version);
 141                 return;
 142         }
 143
 144         // Check Header checksum
 145         {
 146                 Uint16  hdrVal, compVal;
 147                 hdrVal = hdr->HeaderChecksum;
 148                 hdr->HeaderChecksum = 0;
 149                 compVal = IPv4_Checksum(hdr, hdr->HeaderLength);
 150                 if(hdrVal != compVal) {
 151                         Log_Log("IPv4", "Header checksum fails (%04x != %04x)", hdrVal, compVal);
 152                         return ;
 153                 }
 154                 hdr->HeaderChecksum = hdrVal;
 155         }
 156
 157         // Check Packet length
 158         if( ntohs(hdr->TotalLength) > Length) {
 159                 Log_Log("IPv4", "hdr->TotalLength(%i) > Length(%i)", ntohs(hdr->TotalLength), Length);
 160                 return;
 161         }
 162
 163         // TODO: Handle packet fragmentation
 164
 165
 166         // Get Data and Data Length
 167         dataLength = ntohs(hdr->TotalLength) - sizeof(tIPv4Header);
 168         data = &hdr->Options[0];
 169
 170         // Get Interface (allowing broadcasts)
 171         iface = IPv4_GetInterface(Adapter, hdr->Destination, 1);
 172
 173         // Firewall rules
 174         if( iface ) {
 175                 // Incoming Packets
 176                 ret = IPTablesV4_TestChain("INPUT",
 177                         &hdr->Source, &hdr->Destination,
 178                         hdr->Protocol, 0,
 179                         dataLength, data
 180                         );
 181         }
 182         else {
 183                 // Routed packets
 184                 ret = IPTablesV4_TestChain("FORWARD",
 185                         &hdr->Source, &hdr->Destination,
 186                         hdr->Protocol, 0,
 187                         dataLength, data
 188                         );
 189         }
 190         switch(ret)
 191         {
 192         // 0 - Allow
 193         case 0: break;
 194         // 1 - Silent Drop
 195         case 1:
 196                 Log_Debug("IPv4", "Silently dropping packet");
 197                 return ;
 198         // Unknown, silent drop
 199         default:
 200                 return ;
 201         }
 202
 203         // Routing
 204         if(!iface)
 205         {
 206                 Log_Debug("IPv4", "Route the packet");
 207
 208                 // TODO: Parse Routing tables and determine where to send it
 209
 210                 return ;
 211         }
 212
 213         // Send it on
 214         if( gaIPv4_Callbacks[hdr->Protocol] )
 215                 gaIPv4_Callbacks[hdr->Protocol]( iface, &hdr->Source, dataLength, data );
 216         else
 217                 Log_Log("IPv4", "Unknown Protocol %i", hdr->Protocol);
 218 }
 219
 220 /**
 221  * \fn tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address)
 222  * \brief Searches an adapter for a matching address
 223  * \param Adapter       Incoming Adapter
 224  * \param Address       Destination Address
 225  * \param Broadcast     Allow broadcast packets
 226  */
 227 tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address, int Broadcast)
 228 {
 229         tInterface      *iface = NULL;
 230         Uint32  netmask;
 231         Uint32  addr, this;
 232
 233         addr = ntohl( Address.L );
 234
 235         for( iface = gIP_Interfaces; iface; iface = iface->Next)
 236         {
 237                 if( iface->Adapter != Adapter ) continue;
 238                 if( iface->Type != 4 )  continue;
 239                 if( IP4_EQU(Address, *(tIPv4*)iface->Address) )
 240                         return iface;
 241
 242                 if( !Broadcast )        continue;
 243
 244                 this = ntohl( ((tIPv4*)iface->Address)->L );
 245
 246                 // Check for broadcast
 247                 netmask = IPv4_Netmask(iface->SubnetBits);
 248
 249                 if( (addr & netmask) == (this & netmask)
 250                  && (addr & ~netmask) == (0xFFFFFFFF & ~netmask) )
 251                         return iface;
 252         }
 253         return NULL;
 254 }
 255
 256 /**
 257  * \brief Convert a network prefix to a netmask
 258  * \param FixedBits     Netmask size (/n)
 259  *
 260  * For example /24 will become 255.255.255.0
 261  */
 262 Uint32 IPv4_Netmask(int FixedBits)
 263 {
 264         Uint32  ret = 0xFFFFFFFF;
 265         ret >>= (32-FixedBits);
 266         ret <<= (32-FixedBits);
 267         // Returns a native endian netmask
 268         return ret;
 269 }
 270
 271 /**
 272  * \brief Calculate the IPv4 Checksum
 273  * \param Buf   Input buffer
 274  * \param Size  Size of input
 275  *
 276  * One's complement sum of all 16-bit words (bitwise inverted)
 277  */
 278 Uint16 IPv4_Checksum(const void *Buf, int Size)
 279 {
 280         Uint16  sum = 0;
 281         const Uint16    *arr = Buf;
 282          int    i;
 283
 284         Size = (Size + 1) >> 1; // 16-bit word count
 285         for(i = 0; i < Size; i++ )
 286         {
 287                 Uint16  val = ntohs(arr[i]);
 288                 if((int)sum + val > 0xFFFF)
 289                         sum ++; // Simulate 1's complement
 290                 sum += val;
 291         }
 292         return ~sum ;
 293 }
 294
 295 /**
 296  * \brief Sends an ICMP Echo and waits for a reply
 297  * \param IFace Interface
 298  * \param Addr  Destination address
 299  */
 300 int IPv4_Ping(tInterface *IFace, tIPv4 Addr)
 301 {
 302         return ICMP_Ping(IFace, Addr);
 303 }