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         const tMacAddr  zero = {{0,0,0,0,0,0}};
  68          int    bufSize = sizeof(tIPv4Header) + Length;
  69         char    buf[bufSize];
  70         tIPv4Header     *hdr = (void*)buf;
  71          int    ret;
  72
  73         if( MAC_EQU(to, zero) ) {
  74                 return 0;
  75         }
  76
  77         // OUTPUT Firewall rule go here
  78         ret = IPTablesV4_TestChain("OUTPUT",
  79                 (tIPv4*)Iface->Address, &Address,
  80                 Protocol, 0,
  81                 Length, Data);
  82         if(ret != 0) {
  83                 // Just drop it (with an error)
  84                 return 0;
  85         }
  86
  87         memcpy(&hdr->Options[0], Data, Length);
  88         hdr->Version = 4;
  89         hdr->HeaderLength = sizeof(tIPv4Header)/4;
  90         hdr->DiffServices = 0;  // TODO: Check
  91
  92         hdr->Reserved = 0;
  93         hdr->DontFragment = 0;
  94         hdr->MoreFragments = 0;
  95         hdr->FragOffLow = 0;
  96         hdr->FragOffHi = 0;
  97
  98         hdr->TotalLength = htons( bufSize );
  99         hdr->Identifcation = htons( ID );       // TODO: Check
 100         hdr->TTL = DEFAULT_TTL;
 101         hdr->Protocol = Protocol;
 102         hdr->HeaderChecksum = 0;        // Will be set later
 103         hdr->Source = *(tIPv4*)Iface->Address;
 104         hdr->Destination = Address;
 105         hdr->HeaderChecksum = IPv4_Checksum(hdr, sizeof(tIPv4Header));
 106
 107         Log_Log("IPv4", "Sending packet to %i.%i.%i.%i",
 108                 Address.B[0], Address.B[1], Address.B[2], Address.B[3]);
 109         Link_SendPacket(Iface->Adapter, IPV4_ETHERNET_ID, to, bufSize, buf);
 110         return 1;
 111 }
 112
 113 /**
 114  * \fn void IPv4_int_GetPacket(tInterface *Adapter, tMacAddr From, int Length, void *Buffer)
 115  * \brief Process an IPv4 Packet
 116  */
 117 void IPv4_int_GetPacket(tAdapter *Adapter, tMacAddr From, int Length, void *Buffer)
 118 {
 119         tIPv4Header     *hdr = Buffer;
 120         tInterface      *iface;
 121         Uint8   *data;
 122          int    dataLength;
 123          int    ret;
 124
 125         if(Length < sizeof(tIPv4Header))        return;
 126
 127         #if 0
 128         //Log_Log("IPv4", "Version = %i", hdr->Version);
 129         //Log_Log("IPv4", "HeaderLength = %i", hdr->HeaderLength);
 130         //Log_Log("IPv4", "DiffServices = %i", hdr->DiffServices);
 131         Log_Debug("IPv4", "TotalLength = %i", ntohs(hdr->TotalLength) );
 132         //Log_Log("IPv4", "Identifcation = %i", ntohs(hdr->Identifcation) );
 133         //Log_Log("IPv4", "TTL = %i", hdr->TTL );
 134         Log_Debug("IPv4", "Protocol = %i", hdr->Protocol );
 135         //Log_Log("IPv4", "HeaderChecksum = 0x%x", ntohs(hdr->HeaderChecksum) );
 136         Log_Debug("IPv4", "Source = %i.%i.%i.%i",
 137                 hdr->Source.B[0], hdr->Source.B[1], hdr->Source.B[2], hdr->Source.B[3] );
 138         Log_Debug("IPv4", "Destination = %i.%i.%i.%i",
 139                 hdr->Destination.B[0], hdr->Destination.B[1],
 140                 hdr->Destination.B[2], hdr->Destination.B[3] );
 141         #endif
 142
 143         // Check that the version IS IPv4
 144         if(hdr->Version != 4) {
 145                 Log_Log("IPv4", "hdr->Version(%i) != 4", hdr->Version);
 146                 return;
 147         }
 148
 149         // Check Header checksum
 150         {
 151                 Uint16  hdrVal, compVal;
 152                 hdrVal = hdr->HeaderChecksum;
 153                 hdr->HeaderChecksum = 0;
 154                 compVal = IPv4_Checksum(hdr, hdr->HeaderLength);
 155                 if(hdrVal != compVal) {
 156                         Log_Log("IPv4", "Header checksum fails (%04x != %04x)", hdrVal, compVal);
 157                         return ;
 158                 }
 159                 hdr->HeaderChecksum = hdrVal;
 160         }
 161
 162         // Check Packet length
 163         if( ntohs(hdr->TotalLength) > Length) {
 164                 Log_Log("IPv4", "hdr->TotalLength(%i) > Length(%i)", ntohs(hdr->TotalLength), Length);
 165                 return;
 166         }
 167
 168         // TODO: Handle packet fragmentation
 169
 170
 171         // Get Data and Data Length
 172         dataLength = ntohs(hdr->TotalLength) - sizeof(tIPv4Header);
 173         data = &hdr->Options[0];
 174
 175         // Get Interface (allowing broadcasts)
 176         iface = IPv4_GetInterface(Adapter, hdr->Destination, 1);
 177
 178         // Firewall rules
 179         if( iface ) {
 180                 // Incoming Packets
 181                 ret = IPTablesV4_TestChain("INPUT",
 182                         &hdr->Source, &hdr->Destination,
 183                         hdr->Protocol, 0,
 184                         dataLength, data
 185                         );
 186         }
 187         else {
 188                 // Routed packets
 189                 ret = IPTablesV4_TestChain("FORWARD",
 190                         &hdr->Source, &hdr->Destination,
 191                         hdr->Protocol, 0,
 192                         dataLength, data
 193                         );
 194         }
 195         switch(ret)
 196         {
 197         // 0 - Allow
 198         case 0: break;
 199         // 1 - Silent Drop
 200         case 1:
 201                 Log_Debug("IPv4", "Silently dropping packet");
 202                 return ;
 203         // Unknown, silent drop
 204         default:
 205                 return ;
 206         }
 207
 208         // Routing
 209         if(!iface)
 210         {
 211                 Log_Debug("IPv4", "Route the packet");
 212
 213                 // TODO: Parse Routing tables and determine where to send it
 214
 215                 return ;
 216         }
 217
 218         // Send it on
 219         if( gaIPv4_Callbacks[hdr->Protocol] )
 220                 gaIPv4_Callbacks[hdr->Protocol]( iface, &hdr->Source, dataLength, data );
 221         else
 222                 Log_Log("IPv4", "Unknown Protocol %i", hdr->Protocol);
 223 }
 224
 225 /**
 226  * \fn tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address)
 227  * \brief Searches an adapter for a matching address
 228  * \param Adapter       Incoming Adapter
 229  * \param Address       Destination Address
 230  * \param Broadcast     Allow broadcast packets
 231  */
 232 tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address, int Broadcast)
 233 {
 234         tInterface      *iface = NULL;
 235         Uint32  netmask;
 236         Uint32  addr, this;
 237
 238         addr = ntohl( Address.L );
 239
 240         for( iface = gIP_Interfaces; iface; iface = iface->Next)
 241         {
 242                 if( iface->Adapter != Adapter ) continue;
 243                 if( iface->Type != 4 )  continue;
 244                 if( IP4_EQU(Address, *(tIPv4*)iface->Address) )
 245                         return iface;
 246
 247                 if( !Broadcast )        continue;
 248
 249                 this = ntohl( ((tIPv4*)iface->Address)->L );
 250
 251                 // Check for broadcast
 252                 netmask = IPv4_Netmask(iface->SubnetBits);
 253
 254                 if( (addr & netmask) == (this & netmask)
 255                  && (addr & ~netmask) == (0xFFFFFFFF & ~netmask) )
 256                         return iface;
 257         }
 258         return NULL;
 259 }
 260
 261 /**
 262  * \brief Convert a network prefix to a netmask
 263  * \param FixedBits     Netmask size (/n)
 264  *
 265  * For example /24 will become 255.255.255.0
 266  */
 267 Uint32 IPv4_Netmask(int FixedBits)
 268 {
 269         Uint32  ret = 0xFFFFFFFF;
 270         ret >>= (32-FixedBits);
 271         ret <<= (32-FixedBits);
 272         // Returns a native endian netmask
 273         return ret;
 274 }
 275
 276 /**
 277  * \brief Calculate the IPv4 Checksum
 278  * \param Buf   Input buffer
 279  * \param Size  Size of input
 280  *
 281  * One's complement sum of all 16-bit words (bitwise inverted)
 282  */
 283 Uint16 IPv4_Checksum(const void *Buf, int Size)
 284 {
 285         Uint16  sum = 0;
 286         const Uint16    *arr = Buf;
 287          int    i;
 288
 289         Size = (Size + 1) >> 1; // 16-bit word count
 290         for(i = 0; i < Size; i++ )
 291         {
 292                 Uint16  val = ntohs(arr[i]);
 293                 if((int)sum + val > 0xFFFF)
 294                         sum ++; // Simulate 1's complement
 295                 sum += val;
 296         }
 297         return ~sum ;
 298 }
 299
 300 /**
 301  * \brief Sends an ICMP Echo and waits for a reply
 302  * \param IFace Interface
 303  * \param Addr  Destination address
 304  */
 305 int IPv4_Ping(tInterface *IFace, tIPv4 Addr)
 306 {
 307         return ICMP_Ping(IFace, Addr);
 308 }