C51 COMPILER V7.50   IP                                                                    12/14/2006 13:34:44 PAGE 1   


C51 COMPILER V7.50, COMPILATION OF MODULE IP
OBJECT MODULE PLACED IN IP.OBJ
COMPILER INVOKED BY: C:\Keil\C51\BIN\C51.EXE IP.C LARGE OPTIMIZE(9,SPEED) BROWSE DEBUG OBJECTEXTEND

line level    source

   1          //-----------------------------------------------------------------------------
   2          // Copyright (c) 2002 Jim Brady
   3          // Do not use commercially without author's permission
   4          // Last revised August 2002
   5          // Net IP.C
   6          //
   7          // This module is the IP layer
   8          // Refer to RFC 791, 1122, and RFC 815 (fragmentation)
   9          //-----------------------------------------------------------------------------
  10          #include <string.h>
  11          #include "C8051f040.h"
  12          #include "net.h"
  13          #include "cksum.h"
  14          #include "arp.h"
  15          #include "icmp.h"
  16          #include "udp.h"
  17          #include "tcp.h"
  18          #include "ip.h"
  19          
  20          extern UCHAR idata debug;
  21          extern ULONG code my_ipaddr;
  22          WAIT xdata wait;
  23          
  24          
  25          //------------------------------------------------------------------------
  26          // This handles outgoing IP datagrams.  It adds the 20 byte IP header
  27          // and checksum then forwards the IP datagram to the Ethernet layer
  28          // for sending. See "TCP/IP Illustrated, Volume 1" Sect 3.2
  29          //------------------------------------------------------------------------
  30          void ip_send(UCHAR xdata * outbuf, ULONG ipaddr, UCHAR proto_id, UINT len)
  31          {
  32   1         IP_HEADER xdata * ip;
  33   1         UCHAR xdata * hwaddr;
  34   1         static UINT ip_ident = 0;
  35   1         
  36   1         ip = (IP_HEADER xdata *)(outbuf + 14);
  37   1         ip->ver_len = 0x45;          // IPv4 with 20 byte header
  38   1         ip->type_of_service = 0;
  39   1         ip->total_length = 20 + len;
  40   1         ip->identifier = ip_ident++;     // sequential identifier
  41   1         ip->fragment_info = 0;           // not fragmented
  42   1         ip->time_to_live = 32;           // max hops
  43   1         ip->protocol_id = proto_id;      // type of payload
  44   1         ip->header_cksum = 0;
  45   1         ip->source_ipaddr = my_ipaddr;
  46   1         
  47   1         // Outgoing IP address
  48   1         ip->dest_ipaddr = ipaddr;
  49   1      
  50   1         // Compute and insert complement of checksum of ip header
  51   1         // Outgoing ip header length is always 20 bytes
  52   1         ip->header_cksum = ~cksum(outbuf + 14, 20);
  53   1         
  54   1         // Use ARP to get hardware address to send this to
  55   1         hwaddr = arp_resolve(ip->dest_ipaddr);
C51 COMPILER V7.50   IP                                                                    12/14/2006 13:34:44 PAGE 2   

  56   1              
  57   1              // Null means that the ARP resolver did not find the IP address
  58   1              // in its cache so had to send an ARP request
  59   1              if (hwaddr == NULL)
  60   1              {
  61   2                      // Fill in the destination information so ehrn the ARP response
  62   2                      // arrives we can identify it and know what to do when we get it
  63   2            wait.buf = outbuf;
  64   2                      wait.ipaddr = ip->dest_ipaddr;
  65   2                      wait.proto_id = proto_id;
  66   2                      wait.len = len;
  67   2                      wait.timer = ARP_TIMEOUT; 
  68   2            return;
  69   2              }       
  70   1              
  71   1              eth_send(outbuf, hwaddr, IP_PACKET, 20 + len);
  72   1      }
  73          
  74          
  75          
  76          //------------------------------------------------------------------------
  77          // This handles incoming IP datagrams from the Ethernet layer
  78          // See "TCP/IP Illustrated, Volume 1" Sect 3.2
  79          //------------------------------------------------------------------------
  80          void ip_rcve(UCHAR xdata * inbuf)
  81          {
  82   1              IP_HEADER xdata * ip;
  83   1              UINT idata header_len, payload_len;
  84   1                      
  85   1         ip = (IP_HEADER xdata *)(inbuf + 14);
  86   1                  
  87   1         // Make sure it is addressed to my IP address
  88   1         if (ip->dest_ipaddr != my_ipaddr) return;
  89   1      
  90   1         // Validate checksum of ip header
  91   1              header_len = 4 * (0x0F & ip->ver_len);
  92   1              payload_len = ip->total_length - header_len;
  93   1         if (cksum(inbuf + 14, header_len) != 0xFFFF)
  94   1              {
  95   2                 return; 
  96   2         }
  97   1              
  98   1              // Make sure incoming message is IP version 4
  99   1              if ((ip->ver_len >> 4) != 0x04)
 100   1              {
 101   2              return;
 102   2              }
 103   1      
 104   1              // Make sure incoming message is not fragmented because
 105   1         // we cannot handle fragmented messages
 106   1         if ((ip->fragment_info & 0x3FFF) != 0)
 107   1         {
 108   2                 return; 
 109   2         }
 110   1      
 111   1         // At this point we have received a valid IP datagram addressed
 112   1         // to me.  We do not use header options, and do not forward
 113   1         // messages, so in the unlikely event there are header options,
 114   1         // delete them and shift the data down. The advantage is that
 115   1         // layers such as UDP and TCP know where their data starts
 116   1              if (header_len > 20)
 117   1              {
C51 COMPILER V7.50   IP                                                                    12/14/2006 13:34:44 PAGE 3   

 118   2                              
 119   2            // Use memmove because of overlap
 120   2            memmove(inbuf + 34, inbuf + 14 + header_len, payload_len);
 121   2      
 122   2                      // Adjust info to reflect the move
 123   2                      header_len = 20;
 124   2                      ip->ver_len = 0x45;
 125   2                      ip->total_length = 20 + payload_len;
 126   2              }
 127   1              
 128   1              
 129   1              // Look at protocol ID byte and call the appropriate
 130   1         // function to handle the received message.  See 
 131   1         // "TCP/IP Illustrated, Volume 1" Sect 1.7 and RFC 791
 132   1         // for values for various protocols
 133   1         switch (ip->protocol_id)
 134   1              {
 135   2                 case ICMP_TYPE:
 136   2            icmp_rcve(inbuf, payload_len);
 137   2                      break;
 138   2      
 139   2            case IGMP_TYPE:
 140   2                ;
 141   2                      // We cannot handle IGMP messages
 142   2                      break;
 143   2                        
 144   2                      case UDP_TYPE:
 145   2            udp_rcve(inbuf, payload_len);
 146   2                      break;
 147   2      
 148   2                      case TCP_TYPE:   
 149   2            tcp_rcve(inbuf, payload_len);
 150   2                      break;
 151   2      
 152   2            default:
 153   2            ;
 154   2            break;
 155   2         }
 156   1      }
 157          
 158          
 159          


MODULE INFORMATION:   STATIC OVERLAYABLE
   CODE SIZE        =    708    ----
   CONSTANT SIZE    =   ----    ----
   XDATA SIZE       =     12      15
   PDATA SIZE       =   ----    ----
   DATA SIZE        =   ----    ----
   IDATA SIZE       =   ----       4
   BIT SIZE         =   ----    ----
END OF MODULE INFORMATION.


C51 COMPILATION COMPLETE.  0 WARNING(S),  0 ERROR(S)