基于Linux的网络数据帧捕获方法与思考 - Linux - 新闻中心

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     基于Linux的网络数据帧捕获方法与思考
  · 魏星浦仕超·CPCW

  Linux的本地化应该以提高大量应用程序的使用和分析为突破口。

  　　目前，国内推出了许多的Linux的发行版本，其重点集中在中文平台上，方便了国内用户对Linux的使用，但是有一个不是太好的迹象就是把汉化作为Linux操作系统的主要功能，实际上汉字处理尽管非常重要，但是把Linux作为桌面系统进行推广，其价值不是非常大，并且在推出的发行版本中，应用程序的源代码包多被删除，而选择了一些不是太有价值的X-Windows程序包，而许多应用程序（如PHP3）必须要源代码的支持才可进行功能的扩展，GNU/Linux的优秀主要是给了我们非常丰富的软件资源，和享受资源的充分自由，应用程序的分析难度远小于内核，并且能够带来比较明显的效果，实际上许多的应用程序都提供了多平台的支持。Linux目前可能作为对抗Windows NT的工具是非常合适的。

  附源程序：

  /*

  * This program demonstrate SOCK_PACK call.

  * Thanks Linux. Thanks Alan Cox

  * derived from/usr/src/redhat/SOURCES/dosemu-0.66.7/src/dosext/net/net/libpacket.c

  *　 compile method： cc capturer.c -o capturer

  */

  /*

  * Alan Cox raw code

  */


  /*

  * SOCK_PACKET support.

  * Placed under the GNU LGPL.

  *

  * First cut at a library of handy support routines. Comments, additions

  * and bug fixes greatfully received.

  *

  * (c) 1994 Alan Cox iiitac@pyr.swan.ac.uk GW4PTS@GB7SWN

  */

  #include <stdio.h>

  #include <features.h>

  #include <unistd.h>

  #include <stdlib.h>

  #include <ctype.h>

  #include <getopt.h>

  #include <string.h>

  #include <fcntl.h>

  #include <asm/types.h>

  #include <sys/socket.h>

  #include <sys/ioctl.h>

  /*#if __GLIBC__ > 1*/

  #include <asm/sockios.h>

  #include <net/if.h>

  /*#else

  #include <linux/sockios.h>

  #include <linux/if.h>

  #endif*/

  #include <netinet/in.h>

  #include <asm/checksum.h>

  /*

  * Obtain a file handle on a raw ethernet type. In actual fact

  * you can also request the dummy types for AX.25 or 802.3 also

  *

  * -1 indicates an error

  * 0 or higher is a file descriptor which we have set non blocking

  *

  * WARNING: It is ok to listen to a service the system is using (eg arp)

  * but don't try and run a user mode stack on the same service or all

  * hell will break loose.

  */

  int

  OpenNetworkType(unsigned short netid)

  {

  int s = socket(AF_INET, SOCK_PACKET, htons(netid));


  if (s == -1)

  return -1;

  fcntl(s, F_SETFL, O_NDELAY);

  return s;

  }


  /*

  * Close a file handle to a raw packet type.

  */


  void

  CloseNetworkLink(int sock)

  {

  close(sock);

  }


  /*

  * Write a packet to the network. You have to give a device to

  * this function. This is a device name (eg 'eth0' for the first

  * ethernet card). Please don't assume eth0, make it configurable

  * - plip is ethernet like but not eth0, ditto for the de600's.

  *

  * Return: -1 is an error

  * otherwise bytes written.

  */

  int

  WriteToNetwork(int sock, const char *device, const char *data, int len)

  {

  struct sockaddr sa;

  sa.sa_family = AF_INET;

  strcpy(sa.sa_data, device);

  return (sendto(sock, data, len, 0, &sa, sizeof(sa)));

  }

  /*

  * Read a packet from the network. The device parameter will

  * be filled in by this routine (make it 32 bytes or more).

  * If you wish to work with one interface only you must filter

  * yourself. Remember to make your buffer big enough for your

  * data. Oversized packets will be truncated.

  *

  * Return:

  * -1 Error

  * otherwise Size of packet received.

  */

  int

  ReadFromNetwork(int sock, char *device, char *data, int len)

  {

  struct sockaddr sa;

  int sz = sizeof(sa);

  int error;

  error = recvfrom(sock, data, len, 0, &sa, &sz);

  if (error == -1)

  return -1;

  strcpy(device, sa.sa_data);

  return error; /* Actually size of received packet */

  }

  /*

  * Handy support routines.

  */

  /*

  * Obtain the hardware address of an interface.

  * addr should be a buffer of 8 bytes or more.

  *

  * Return:

  * 0 Success, buffer holds data.

  * -1 Error.

  */


  /*

  * NET2 or NET3 - work for both.

  */

  #if defined(OLD_SIOCGIFHWADDR) || (KERNEL_VERSION >= 1003038)

  #define NET3

  #endif


  int

  GetDeviceHardwareAddress(char *device, char *addr)

  {

  int s = socket(AF_INET, SOCK_DGRAM, 0);

  struct ifreq req;

  int err;

  strcpy(req.ifr_name, device);

  err = ioctl(s, SIOCGIFHWADDR, &req);

  close(s); /* Thanks Rob. for noticing this */

  if (err == -1)

  return err;

  memcpy(addr, req.ifr_hwaddr.sa_data,8);

  return 0;

  }

  /*

  * Obtain the maximum packet size on an interface.

  *

  * Return:

  * >0 Return is the mtu of the interface

  * -1 Error.

  */

  int

  GetDeviceMTU(char *device)

  {

  int s = socket(AF_INET, SOCK_DGRAM, 0);

  struct ifreq req;

  int err;

  strcpy(req.ifr_name, device);

  err = ioctl(s, SIOCGIFMTU, &req);

  close(s); /* So I'll add this one as well. Ok Alan? - Rob */

  if (err == -1)

  return err;

  return req.ifr_mtu;

  }

  #define data_packet_len 1514

  int

  main(int argc ,char *argv[])

  {

  char devicename_rec[32];

  unsigned char data[data_packet_len];

  int netid=0x03,sock_h=0,i=0,count_rec=0;

  if ((sock_h=OpenNetworkType(netid))<0)

  {

  printf("Can't open net_dectype %d \n",netid);

  return -1;

  }

  printf("Ready to receive 0x%x data packet...\n",netid);

  for(;;) {

  if (ReadFromNetwork(sock_h,devicename_rec,data,data_packet_len)>0) {

  printf("Received Packet = %d\n",++count_rec) ;

  for (i=0;i<100;i++)

  printf("%2x|",data[i]);

  printf("\n");

  }

  }

  }


  /*以上程序在Redhat 5.1下编译通过，运行良好。*/