firmware/ip.c (2342395) - flaneth · BlinkenArea

ip.c

/* flaneth - flash and ethernet
   Copyright (C) 2007-2012 Stefan Schuermans <stefan@blinkenarea.org>
   Copyleft: GNU public license V2 - http://www.gnu.org/copyleft/gpl.html
   a BlinkenArea project - http://www.blinkenarea.org/ */

#include <string.h>

#include "arp.h"
#include "checksum.h"
#include "config.h"
#include "debug.h"
#include "ethernet.h"
#include "icmp.h"
#include "ip.h"
#include "macros.h"
#include "nethelp.h"
#include "tcp.h"
#include "udp.h"

// timing parameters
#define IpBufferTicksMax 50     // maximum age of buffered IP packet (in
                                // 200ms steps)

// buffers for IP packets to transmit
// - used if MAC is unknown when packet shall be transmitted
// - packet is sent when MAC becomes known
unsigned char IpBuffer0[80];    // some buffers with different length (IP
                                // packets have different length)
unsigned char IpBuffer1[80];
unsigned char IpBuffer2[160];
unsigned char IpBuffer3[320];
struct IpBufferTable    // table with buffers
{
  unsigned char *pBuffer;       // pointer to buffer for packet
  unsigned short BufferLength;  // length of buffer
  unsigned short PacketLength;  // length of packet in buffer, 0 if no packet 
                                // in this buffer
  unsigned char Ticks;  // age of entry in 200ms steps
} IpBufferTab[] = {     // put smaller buffers in front of larger buffers
  // - then short packets will use smaller buffers more often
  {
  IpBuffer0, sizeof(IpBuffer0), 0, 0}
  , {
  IpBuffer1, sizeof(IpBuffer1), 0, 0}
  , {
  IpBuffer2, sizeof(IpBuffer2), 0, 0}
  , {
  IpBuffer3, sizeof(IpBuffer3), 0, 0}
,};

// tick procedure - call every 200ms
void IpTick200(void)    // (extern)
{
  unsigned char i;

// increase age of buffered IP packets and remove timed out ones
  for (i = 0; i < count(IpBufferTab); i++) {
    if (IpBufferTab[i].PacketLength > 0)        // buffer in use
    {
      IpBufferTab[i].Ticks++;   // increase age
      if (IpBufferTab[i].Ticks > IpBufferTicksMax)      // too old
        IpBufferTab[i].PacketLength = 0;        // discard packet
    }
  }
}

// process a received IP packet
void IpRecv(unsigned char *pData, unsigned short Length)        // (extern)
{
  struct IpPacket *pIpPack;
  unsigned int len;

// packet too short
  if (Length < sizeof(struct IpPacket))
    return;

// convert pointer to IP packet
  // (this saves us from always casting pData)
  pIpPack = (struct IpPacket *)pData;

// not IPv4
  if (pIpPack->IpHdr.Ver_HdrLen != 0x45)        // IPv4 with no options
                                                // present
    return;

// check destination address
  do {
    if (ip_eq(pIpPack->IpHdr.Dest, ConfigIp))   // own IP
      break;
    if (ip_eq(pIpPack->IpHdr.Dest, "\xFF\xFF\xFF\xFF")) // broadcast
      break;
    if (pIpPack->IpHdr.Dest[0] == (ConfigIp[0] & ConfigMask[0]) &&      // local 
                                                                        // broadcast
        pIpPack->IpHdr.Dest[1] == (ConfigIp[1] & ConfigMask[1]) &&
        pIpPack->IpHdr.Dest[2] == (ConfigIp[2] & ConfigMask[2]) &&
        pIpPack->IpHdr.Dest[3] == (ConfigIp[3] & ConfigMask[3]))
      break;
    return;     // packet not to this node
  } while (0);

// ignore packets sent from invalid source adresses
  // - this might be some attack or some router fault
  if (pIpPack->IpHdr.Src[0] >= 0xE0 ||  // broadcast, reserved or multicast
                                        // addresses
      pIpPack->IpHdr.Src[0] == 0x7F ||  // loopback network
      ip_eq(pIpPack->IpHdr.Src, "\x00\x00\x00\x00"))    // IP 0.0.0.0
    return;
  // ignore packets sent from local network address or broadcast address
  if ((pIpPack->IpHdr.Src[0] & ConfigMask[0]) == (ConfigIp[0] & ConfigMask[0]) &&       // source 
                                                                                        // IP 
                                                                                        // is 
                                                                                        // in 
                                                                                        // own 
                                                                                        // subnet
      (pIpPack->IpHdr.Src[1] & ConfigMask[1]) == (ConfigIp[1] & ConfigMask[1])
      && (pIpPack->IpHdr.Src[2] & ConfigMask[2]) ==
      (ConfigIp[2] & ConfigMask[2])
      && (pIpPack->IpHdr.Src[3] & ConfigMask[3]) ==
      (ConfigIp[3] & ConfigMask[3])) {
    if ((pIpPack->IpHdr.Src[0] & ~ConfigMask[0]) == 0x00 &&     // local
                                                                // network
                                                                // address
        (pIpPack->IpHdr.Src[1] & ~ConfigMask[1]) == 0x00 &&
        (pIpPack->IpHdr.Src[2] & ~ConfigMask[2]) == 0x00 &&
        (pIpPack->IpHdr.Src[3] & ~ConfigMask[3]) == 0x00)
      return;
    if ((pIpPack->IpHdr.Src[0] & ~ConfigMask[0]) == 0xFF &&     // local
                                                                // broadcast
                                                                // address
        (pIpPack->IpHdr.Src[1] & ~ConfigMask[1]) == 0xFF &&
        (pIpPack->IpHdr.Src[2] & ~ConfigMask[2]) == 0xFF &&
        (pIpPack->IpHdr.Src[3] & ~ConfigMask[3]) == 0xFF)
      return;
  }
  // ignore packets sent from own IP address
  if (ip_eq(pIpPack->IpHdr.Src, ConfigIp))
    return;

// ignore fragmented packets
  // BUG: fragmentation must be supported according to RFC781
  // but there is no way of assembling packets with up to 64kB on a processor 
  // with 4kB of RAM
  if ((ntohs(pIpPack->IpHdr.FragOfs) & 0xBFFF) != 0x0000)       // fragment
                                                                // offset 0,
                                                                // MoreFrags=0, 
                                                                // DontFrag=x, 
                                                                // reservedFlag=0
    return;

// check total length
  len = sizeof(struct EthernetHeader) + ntohs(pIpPack->IpHdr.TotalLen); // length 
                                                                        // according 
                                                                        // to 
                                                                        // IP 
                                                                        // header
  if (Length < len)     // packet is truncated
    return;
  Length = len; // remove ethernet padding from packet (maybe Length > len)

// test header checksum
  if (Checksum
      ((unsigned char *)&pIpPack->IpHdr, sizeof(struct IpHeader), 0x0000,
       0x0000) != 0)
    return;

debug_ip_printf("recv src=%u.%u.%u.%u protocol=%u len=%u",
                  pIpPack->IpHdr.Src[0], pIpPack->IpHdr.Src[1],
                  pIpPack->IpHdr.Src[2], pIpPack->IpHdr.Src[3],
                  pIpPack->IpHdr.Proto, Length);

// branch according to protocol
  switch (pIpPack->IpHdr.Proto) {
    // ICMP
  case 0x01:
    IcmpRecv(pData, Length);
    break;
    // TCP
  case 0x06:
    TcpRecv(pData, Length);
    break;
    // UDP
  case 0x11:
    UdpRecv(pData, Length);
    break;
  }
}

// send an IP packet
// pData must point to a struct IpPacket with IpHdr.Proto and IpHdr.Dest
// already initialized
void IpSend(unsigned char *pData, unsigned short Length)        // (extern)
{
  struct IpPacket *pIpPack;
  unsigned int chk;
  unsigned char i;

// packet too short
  if (Length < sizeof(struct IpPacket))
    return;

// convert pointer to IP packet
  // (this saves us from always casting pData)
  pIpPack = (struct IpPacket *)pData;

debug_ip_printf("send dest=%u.%u.%u.%u protocol=%u len=%u",
                  pIpPack->IpHdr.Dest[0], pIpPack->IpHdr.Dest[1],
                  pIpPack->IpHdr.Dest[2], pIpPack->IpHdr.Dest[3],
                  pIpPack->IpHdr.Proto, Length);

// fill in header values
  pIpPack->IpHdr.Ver_HdrLen = 0x45;
  pIpPack->IpHdr.Tos = 0x00;
  pIpPack->IpHdr.TotalLen = htons(Length - sizeof(struct EthernetHeader));
  pIpPack->IpHdr.Id = 0x0000;
  pIpPack->IpHdr.FragOfs = 0x0000;
  pIpPack->IpHdr.Ttl = 0x40;
  pIpPack->IpHdr.HdrChk = 0x0000;
  ip_cpy(pIpPack->IpHdr.Src, ConfigIp);

// generate header checksum
  chk =
      Checksum((unsigned char *)&pIpPack->IpHdr, sizeof(struct IpHeader),
               0x0000, 0x0000);
  pIpPack->IpHdr.HdrChk = htons(chk);

// destination is in own subnet
  if ((pIpPack->IpHdr.Dest[0] & ConfigMask[0]) ==
      (ConfigIp[0] & ConfigMask[0])
      && (pIpPack->IpHdr.Dest[1] & ConfigMask[1]) ==
      (ConfigIp[1] & ConfigMask[1])
      && (pIpPack->IpHdr.Dest[2] & ConfigMask[2]) ==
      (ConfigIp[2] & ConfigMask[2])
      && (pIpPack->IpHdr.Dest[3] & ConfigMask[3]) ==
      (ConfigIp[3] & ConfigMask[3])) {
    // broadcast
    if ((pIpPack->IpHdr.Dest[0] | ConfigMask[0]) == 255 &&
        (pIpPack->IpHdr.Dest[1] | ConfigMask[1]) == 255 &&
        (pIpPack->IpHdr.Dest[2] | ConfigMask[2]) == 255 &&
        (pIpPack->IpHdr.Dest[3] | ConfigMask[3]) == 255) {
      mac_cpy(pIpPack->EthHdr.Dest, "\xFF\xFF\xFF\xFF\xFF\xFF");
      i = 0x00;
    }
    // unicast
    else {
      // lookup MAC address of destination
      i = ArpLookup(pIpPack->IpHdr.Dest, pIpPack->EthHdr.Dest);
    }
  }
  // destination is not in own subnet
  else {
    // broadcast
    if (pIpPack->IpHdr.Dest[0] == 255 &&
        pIpPack->IpHdr.Dest[1] == 255 &&
        pIpPack->IpHdr.Dest[2] == 255 && pIpPack->IpHdr.Dest[3] == 255) {
      mac_cpy(pIpPack->EthHdr.Dest, "\xFF\xFF\xFF\xFF\xFF\xFF");
      i = 0x00;
    }
    // unicast
    else {
      // lookup MAC address of default gateway
      i = ArpLookup(ConfigGw, pIpPack->EthHdr.Dest);
    }
  }

// MAC available
  if (i == 0x00) {
    // sent IP packet
    pIpPack->EthHdr.Type = htons(0x0800);       // ethernet packet type: IP
    EthernetSend(pData, Length);
    return;
  }
  // find a buffer to store the packet in
  for (i = 0; i < count(IpBufferTab); i++) {
    if (IpBufferTab[i].PacketLength == 0 &&     // buffer not in use
        Length < IpBufferTab[i].BufferLength)   // buffer long enough
    {
      // put packet into buffer
      memcpy(IpBufferTab[i].pBuffer, pData, Length);
      IpBufferTab[i].PacketLength = Length;
      IpBufferTab[i].Ticks = 0;
      debug_ip_printf("queued");
      break;
    }
  }
  // if no buffer was found, we cannnot do anything about it and must discard 
  // the packet (i.e. do nothing here)
}

// a MAC address was discovered
// called by ARP to notify IP
void IpGotMac(unsigned char Ip[4], unsigned char Mac[6])        // (extern)
{
  unsigned char i;
  struct IpPacket *pIpPack;

// search for buffered packets that can be sent now
  for (i = 0; i < count(IpBufferTab); i++) {
    if (IpBufferTab[i].PacketLength > 0)        // buffer in use
    {
      // convert pointer to IP packet
      pIpPack = (struct IpPacket *)IpBufferTab[i].pBuffer;

debug_ip_printf("send queued dest=%u.%u.%u.%u protocol=%u len=%u",
                      pIpPack->IpHdr.Dest[0], pIpPack->IpHdr.Dest[1],
                      pIpPack->IpHdr.Dest[2], pIpPack->IpHdr.Dest[3],
                      pIpPack->IpHdr.Proto, IpBufferTab[i].PacketLength);

// destination is in own subnet
      if ((pIpPack->IpHdr.Dest[0] & ConfigMask[0]) ==
          (ConfigIp[0] & ConfigMask[0])
          && (pIpPack->IpHdr.Dest[1] & ConfigMask[1]) ==
          (ConfigIp[1] & ConfigMask[1])
          && (pIpPack->IpHdr.Dest[2] & ConfigMask[2]) ==
          (ConfigIp[2] & ConfigMask[2])
          && (pIpPack->IpHdr.Dest[3] & ConfigMask[3]) ==
          (ConfigIp[3] & ConfigMask[3])) {
        // packet can be sent to destination
        if (ip_eq(pIpPack->IpHdr.Dest, Ip)) {
          // send IP packet
          pIpPack->EthHdr.Type = htons(0x0800); // ethernet packet type: IP
          mac_cpy(pIpPack->EthHdr.Dest, Mac);
          EthernetSend(IpBufferTab[i].pBuffer, IpBufferTab[i].PacketLength);
          // buffer is now free
          IpBufferTab[i].PacketLength = 0;
        }
      }
      // destination is not in own subnet
      else {
        // packet can be sent to gateway
        if (ip_eq(ConfigGw, Ip)) {
          // send IP packet
          pIpPack->EthHdr.Type = htons(0x0800); // ethernet packet type: IP
          mac_cpy(pIpPack->EthHdr.Dest, Mac);
          EthernetSend(IpBufferTab[i].pBuffer, IpBufferTab[i].PacketLength);
          // buffer is now free
          IpBufferTab[i].PacketLength = 0;
        }
      }
    }
  }     // for( i ...
}

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