Question

我正在尝试编写示例Raw套接字程序以清除我对原始套接字的理解。我创建一个Raw UDP套接字，然后调用sendto。我的发送成功但我从未看到对方收到的数据包。我没有任何接收端运行所以我依靠Wireshark在发送器和接收器上运行。我在这里粘贴代码片段。请指出任何错误。

#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<string.h>

#include "protHeaders.x"
#include "gen.h"

U16 csum(U16* buf, S32 nwords)
  {
   U32 sum;
   for (sum = 0; nwords > 0; nwords--)
     sum += *buf++;
   sum = (sum >> 16) + (sum & 0xffff);
   sum += (sum >> 16);


   return ~sum;
  }/*csum*/

 int main(int argc,char** argv)
  {
    U8 datagram[MAX_IPPACKET];
    U8 udpPayLoad[MAX_UDPPAYLOAD];
    CustIpHeader* ipH;
    CustUdpHeader* udpH;
    struct sockaddr_in sin;
    S32 sockFd;
    S32 one = 1;
    const S32* val = &one;


   ipH   = (CustIpHeader *)datagram;
   udpH  = (CustUdpHeader *)(datagram + sizeof(CustIpHeader));

   memset(datagram,0,sizeof(datagram));
   memset(udpPayLoad,0,sizeof(udpPayLoad));
   memset(&sin,0,sizeof(struct sockaddr_in));

   strcpy(udpPayLoad,"<<<<Aditya>>>>");

   sin.sin_family = AF_INET;
   sin.sin_port   = htons(atoi(argv[4]));

   /* fill the Ip header */

    ipH->ip_hl         = 5;
    ipH->ip_v          = 4;
    ipH->ip_tos        = 0;
    ipH->ip_len        = sizeof(CustIpHeader) + sizeof(CustUdpHeader) + strlen(udpPayLoad);
    ipH->ip_id         = htonl(54321);
    ipH->ip_off        = 0;
    ipH->ip_p          = 17;
    ipH->ip_ttl        = 65;
    ipH->ip_sum        = 0;
    ipH->ip_src.s_addr = inet_addr(argv[1]);
    ipH->ip_dst.s_addr = inet_addr(argv[3]);

  /* fill the Udp header */

    udpH->uh_sport     = htons(atoi(argv[2]));
    udpH->uh_dport     = htons(atoi(argv[4]));
    udpH->uh_len       = sizeof(CustUdpHeader) + strlen(udpPayLoad);
    udpH->uh_check     = 0;

   printf("Checksum = %u\n",udpH->uh_check);
  /* copy udpPayLoad */
    strcpy(datagram+sizeof(CustIpHeader)+sizeof(CustUdpHeader),udpPayLoad);
   #if 1
    printf("Datagram %p,UdpPayload %p\n",(void *)datagram,(void *)datagram+sizeof(CustIpHeader)+sizeof(CustUdpHeader));
    printf("IpHeader %p, UdpHeader %p\n",(void *)ipH,udpH);
   #endif

  /* fill in the checksum */

   ipH->ip_sum = csum((U16 *)datagram,ipH->ip_len >> 1);

   printf("Checksum = %u\n",ipH->ip_sum);


  if ((sockFd = socket(PF_INET,SOCK_RAW,IPPROTO_UDP)) < 0)
      {
         perror("socket:create");
         RETURN(RFAILED);
      }
  /* doing the IP_HDRINCL call */

    if (setsockopt(sockFd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one)) < 0)
     {
        perror("Client:setsockopt");
     }


   while(1)
    {
      if ( sendto(sockFd,
                  datagram,
                  ipH->ip_len,
                  0,
                  (struct sockaddr *)&sin,
                  sizeof (sin)) < 0)
           { perror("Client:sendto"); }

      else
           printf(".");

    }

   RETURN(ROK);
  }

IP和UDP标头是：

typedef struct _ipheader
 {
   U8 ip_hl:4,ip_v:4; /* ip_hl: the ip header length in 32bit octets.
                       * ip_v : ip version (always 4 for our case).
                       */

   U8 ip_tos;         /* reliability of the service. 0x00 is Normal */

   U16 ip_len;        /* totoal length including ip header,icmp/tcp/udp header
                       * and payload size in bytes
                       */

   U16 ip_id;         /* sequence no. used for reassembly of fragmented IP packets */

   U16 ip_off;        /* the fragment offset used for reassembly of fragmented packets */

   U16 ip_p;          /* the transport layer protocol. can be tcp (6), udp(17) */


   U8 ip_ttl;         /* time to live */

   U16 ip_sum;        /* the datagram checksum for the whole IP packet */

   struct in_addr ip_src;        /* the source IP address, converted to a long format */

   struct in_addr ip_dst;        /* the desitnation IP address, converted to a long format */
 }CustIpHeader; /* total ip header length: 20 bytes */



typedef struct _udpheader
{

 U16 uh_sport;      /* The source port that a client bind()s to */
 U16 uh_dport;      /* The desination port that a server bind()s to*/
 U16 uh_len;        /* The length of udp header and payload data in bytes */
 U16 uh_check;      /* The checksum of header and data */

}CustUdpHeader; /* total udp header length: 8 bytes (=64 bits) */

我以root用户身份运行，因此权限不是问题。

语言：C

Os：Linux

Answer 1

我让wireshark在慢速系统上运行。数据包确实正在发送，但Wireshark只能在6分钟左右的间隙后显示它们。转向更快的系统有所帮助。因此，我自己就此结束了。

Answer 2

这可以帮助您开始使用http://www.securitytube.net/Raw-Sockets-Basics-Presentation-video.aspx。

如果你使用libcap / wincap我会帮助你。但是上面的视频可以帮助您入门。

原始套接字不发送

2 个答案: