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, size_t Length);
  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         if( MAC_EQU(to, cMAC_ZERO) ) {
  73                 // No route to host
  74                 Log_Notice("IPv4", "No route to host %i.%i.%i.%i",
  75                         Address.B[0], Address.B[1], Address.B[2], Address.B[3]);
  76                 return 0;
  77         }
  78
  79         // OUTPUT Firewall rule go here
  80         ret = IPTables_TestChain("OUTPUT",
  81                 4, (tIPv4*)Iface->Address, &Address,
  82                 Protocol, 0,
  83                 Length, Data);
  84         if(ret > 0) {
  85                 // Just drop it (with an error)
  86                 Log_Notice("IPv4", "Firewall dropped packet");
  87                 return 0;
  88         }
  89
  90         memcpy(&hdr->Options[0], Data, Length);
  91         hdr->Version = 4;
  92         hdr->HeaderLength = sizeof(tIPv4Header)/4;
  93         hdr->DiffServices = 0;  // TODO: Check
  94
  95         hdr->Reserved = 0;
  96         hdr->DontFragment = 0;
  97         hdr->MoreFragments = 0;
  98         hdr->FragOffLow = 0;
  99         hdr->FragOffHi = 0;
 100
 101         hdr->TotalLength = htons( bufSize );
 102         hdr->Identifcation = htons( ID );       // TODO: Check
 103         hdr->TTL = DEFAULT_TTL;
 104         hdr->Protocol = Protocol;
 105         hdr->HeaderChecksum = 0;        // Will be set later
 106         hdr->Source = *(tIPv4*)Iface->Address;
 107         hdr->Destination = Address;
 108         hdr->HeaderChecksum = htons( IPv4_Checksum(hdr, sizeof(tIPv4Header)) );
 109
 110         Log_Log("IPv4", "Sending packet to %i.%i.%i.%i",
 111                 Address.B[0], Address.B[1], Address.B[2], Address.B[3]);
 112         Link_SendPacket(Iface->Adapter, IPV4_ETHERNET_ID, to, bufSize, buf);
 113         return 1;
 114 }
 115
 116 /**
 117  * \fn void IPv4_int_GetPacket(tInterface *Adapter, tMacAddr From, int Length, void *Buffer)
 118  * \brief Process an IPv4 Packet
 119  */
 120 void IPv4_int_GetPacket(tAdapter *Adapter, tMacAddr From, int Length, void *Buffer)
 121 {
 122         tIPv4Header     *hdr = Buffer;
 123         tInterface      *iface;
 124         Uint8   *data;
 125          int    dataLength;
 126          int    ret;
 127
 128         if(Length < sizeof(tIPv4Header))        return;
 129
 130         #if 0
 131         //Log_Log("IPv4", "Version = %i", hdr->Version);
 132         //Log_Log("IPv4", "HeaderLength = %i", hdr->HeaderLength);
 133         //Log_Log("IPv4", "DiffServices = %i", hdr->DiffServices);
 134         Log_Debug("IPv4", "TotalLength = %i", ntohs(hdr->TotalLength) );
 135         //Log_Log("IPv4", "Identifcation = %i", ntohs(hdr->Identifcation) );
 136         //Log_Log("IPv4", "TTL = %i", hdr->TTL );
 137         Log_Debug("IPv4", "Protocol = %i", hdr->Protocol );
 138         //Log_Log("IPv4", "HeaderChecksum = 0x%x", ntohs(hdr->HeaderChecksum) );
 139         Log_Debug("IPv4", "Source = %i.%i.%i.%i",
 140                 hdr->Source.B[0], hdr->Source.B[1], hdr->Source.B[2], hdr->Source.B[3] );
 141         Log_Debug("IPv4", "Destination = %i.%i.%i.%i",
 142                 hdr->Destination.B[0], hdr->Destination.B[1],
 143                 hdr->Destination.B[2], hdr->Destination.B[3] );
 144         #endif
 145
 146         // Check that the version IS IPv4
 147         if(hdr->Version != 4) {
 148                 Log_Log("IPv4", "hdr->Version(%i) != 4", hdr->Version);
 149                 return;
 150         }
 151
 152         // Check Header checksum
 153         {
 154                 Uint16  hdrVal, compVal;
 155                 hdrVal = ntohs(hdr->HeaderChecksum);
 156                 hdr->HeaderChecksum = 0;
 157                 compVal = IPv4_Checksum(hdr, hdr->HeaderLength * 4);
 158                 if(hdrVal != compVal) {
 159                         Log_Log("IPv4", "Header checksum fails (%04x != %04x)", hdrVal, compVal);
 160                         return ;
 161                 }
 162                 hdr->HeaderChecksum = hdrVal;
 163         }
 164
 165         // Check Packet length
 166         if( ntohs(hdr->TotalLength) > Length) {
 167                 Log_Log("IPv4", "hdr->TotalLength(%i) > Length(%i)", ntohs(hdr->TotalLength), Length);
 168                 return;
 169         }
 170
 171         // TODO: Handle packet fragmentation
 172
 173
 174         // Get Data and Data Length
 175         dataLength = ntohs(hdr->TotalLength) - sizeof(tIPv4Header);
 176         data = &hdr->Options[0];
 177
 178         // Get Interface (allowing broadcasts)
 179         iface = IPv4_GetInterface(Adapter, hdr->Destination, 1);
 180
 181         // Firewall rules
 182         if( iface ) {
 183                 // Incoming Packets
 184                 ret = IPTables_TestChain("INPUT",
 185                         4, &hdr->Source, &hdr->Destination,
 186                         hdr->Protocol, 0,
 187                         dataLength, data
 188                         );
 189         }
 190         else {
 191                 // Routed packets
 192                 ret = IPTables_TestChain("FORWARD",
 193                         4, &hdr->Source, &hdr->Destination,
 194                         hdr->Protocol, 0,
 195                         dataLength, data
 196                         );
 197         }
 198         switch(ret)
 199         {
 200         // 0 - Allow
 201         case 0: break;
 202         // 1 - Silent Drop
 203         case 1:
 204                 Log_Debug("IPv4", "Silently dropping packet");
 205                 return ;
 206         case -1:
 207                 // Bad rule
 208                 break ;
 209         // Unknown, silent drop
 210         default:
 211                 Log_Warning("IPv4", "Unknown firewall rule");
 212                 return ;
 213         }
 214
 215         // Routing
 216         if(!iface)
 217         {
 218                 tMacAddr        to;
 219                 tRoute  *rt;
 220
 221                 Log_Debug("IPv4", "Route the packet");
 222                 // Drop the packet if the TTL is zero
 223                 if( hdr->TTL == 0 ) {
 224                         Log_Warning("IPv4", "TODO: Sent ICMP-Timeout when TTL exceeded");
 225                         return ;
 226                 }
 227
 228                 hdr->TTL --;
 229
 230                 rt = IPStack_FindRoute(4, NULL, &hdr->Destination);     // Get the route (gets the interface)
 231                 to = ARP_Resolve4(rt->Interface, hdr->Destination);     // Resolve address
 232                 if( MAC_EQU(to, cMAC_ZERO) )
 233                         return ;
 234
 235                 // Send packet
 236                 Log_Log("IPv4", "Forwarding packet to %i.%i.%i.%i (via %i.%i.%i.%i)",
 237                         hdr->Destination.B[0], hdr->Destination.B[1],
 238                         hdr->Destination.B[2], hdr->Destination.B[3],
 239                         ((tIPv4*)rt->NextHop)->B[0], ((tIPv4*)rt->NextHop)->B[1],
 240                         ((tIPv4*)rt->NextHop)->B[2], ((tIPv4*)rt->NextHop)->B[3]);
 241                 Link_SendPacket(rt->Interface->Adapter, IPV4_ETHERNET_ID, to, Length, Buffer);
 242
 243
 244                 return ;
 245         }
 246
 247         // Send it on
 248         if( !gaIPv4_Callbacks[hdr->Protocol] ) {
 249                 Log_Log("IPv4", "Unknown Protocol %i", hdr->Protocol);
 250                 return ;
 251         }
 252
 253         gaIPv4_Callbacks[hdr->Protocol]( iface, &hdr->Source, dataLength, data );
 254 }
 255
 256 /**
 257  * \fn tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address)
 258  * \brief Searches an adapter for a matching address
 259  * \param Adapter       Incoming Adapter
 260  * \param Address       Destination Address
 261  * \param Broadcast     Allow broadcast packets
 262  */
 263 tInterface *IPv4_GetInterface(tAdapter *Adapter, tIPv4 Address, int Broadcast)
 264 {
 265         tInterface      *iface = NULL;
 266         Uint32  netmask;
 267         Uint32  addr, this;
 268
 269         addr = ntohl( Address.L );
 270
 271         for( iface = gIP_Interfaces; iface; iface = iface->Next)
 272         {
 273                 if( iface->Adapter != Adapter ) continue;
 274                 if( iface->Type != 4 )  continue;
 275                 if( IP4_EQU(Address, *(tIPv4*)iface->Address) )
 276                         return iface;
 277
 278                 if( !Broadcast )        continue;
 279
 280                 this = ntohl( ((tIPv4*)iface->Address)->L );
 281
 282                 // Check for broadcast
 283                 netmask = IPv4_Netmask(iface->SubnetBits);
 284
 285                 if( (addr & netmask) == (this & netmask)
 286                  && (addr & ~netmask) == (0xFFFFFFFF & ~netmask) )
 287                         return iface;
 288         }
 289         return NULL;
 290 }
 291
 292 /**
 293  * \brief Convert a network prefix to a netmask
 294  * \param FixedBits     Netmask size (/n)
 295  *
 296  * For example /24 will become 255.255.255.0 (0xFFFFFF00)
 297  */
 298 Uint32 IPv4_Netmask(int FixedBits)
 299 {
 300         Uint32  ret = 0xFFFFFFFF;
 301         ret >>= (32-FixedBits);
 302         ret <<= (32-FixedBits);
 303         // Returns a native endian netmask
 304         return ret;
 305 }
 306
 307 /**
 308  * \brief Calculate the IPv4 Checksum
 309  * \param Buf   Input buffer
 310  * \param Size  Size of input
 311  *
 312  * One's complement sum of all 16-bit words (bitwise inverted)
 313  */
 314 Uint16 IPv4_Checksum(const void *Buf, size_t Length)
 315 {
 316         const Uint16    *words = Buf;
 317         Uint32  sum = 0;
 318          int    i;
 319
 320         // Sum all whole words
 321         for(i = 0; i < Length/2; i++ )
 322         {
 323                 sum += ntohs(words[i]);
 324         }
 325         if( Length & 1 )
 326                 sum += ntohs( words[i] & 0xFF );
 327
 328         // Apply one's complement
 329         while (sum >> 16)
 330                 sum = (sum & 0xFFFF) + (sum >> 16);
 331
 332         return ~sum;
 333 }
 334
 335 /**
 336  * \brief Sends an ICMP Echo and waits for a reply
 337  * \param IFace Interface
 338  * \param Addr  Destination address
 339  */
 340 int IPv4_Ping(tInterface *IFace, tIPv4 Addr)
 341 {
 342         return ICMP_Ping(IFace, Addr);
 343 }