本文介绍使用PF_PACKET和SOCK_RAW发送自己定义type以太网数据包，使用wireshare抓包能够获取到数据包，为Linux内核添加网络协议做铺垫。

先上码：

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>           // close()

#include <string.h>           // strcpy, memset(), and memcpy()

#include <netdb.h>            // struct addrinfo

#include <sys/types.h>        // needed for socket(), uint8_t, uint16_t, uint32_t

#include <sys/socket.h>       // needed for socket()

#include <netinet/in.h>       // IPPROTO_ICMP, INET_ADDRSTRLEN

#include <netinet/ip.h>       // struct ip and IP_MAXPACKET (which is 65535)

#include <netinet/ip_icmp.h>  // struct icmp, ICMP_ECHO

#include <arpa/inet.h>        // inet_pton() and inet_ntop()

#include <sys/ioctl.h>        // macro ioctl is defined

#include <bits/ioctls.h>      // defines values for argument "request" of ioctl.

#include <net/if.h>           // struct ifreq

#include <linux/if_ether.h>   // ETH_P_IP = 0x0800, ETH_P_IPV6 = 0x86DD

#include <linux/if_packet.h>  // struct sockaddr_ll (see man 7 packet)

#include <net/ethernet.h>



#include <errno.h>            // errno, perror()

#define ETH_P_DEAN 0x8874 //自己定义的以太网协议type



int main (int argc, char **argv)

{

    int i, datalen,frame_length, sd, bytes;

    char *interface="eth1";;

    uint8_t data[IP_MAXPACKET];

    uint8_t src_mac[6];

    uint8_t dst_mac[6];;

    uint8_t ether_frame[IP_MAXPACKET];

    struct sockaddr_ll device;

    struct ifreq ifr;



    // Submit request for a socket descriptor to look up interface.

    if ((sd = socket (PF_PACKET, SOCK_RAW, htons (ETH_P_ALL))) < 0) {//第一次创建socket是为了获取本地网卡信息

        perror ("socket() failed to get socket descriptor for using ioctl() ");

        exit (EXIT_FAILURE);

    }



    // Use ioctl() to look up interface name and get its MAC address.

    memset (&ifr, 0, sizeof (ifr));

    snprintf (ifr.ifr_name, sizeof (ifr.ifr_name), "%s", interface);

    if (ioctl (sd, SIOCGIFHWADDR, &ifr) < 0) {

        perror ("ioctl() failed to get source MAC address ");

        return (EXIT_FAILURE);

    }

    close (sd);



    // Copy source MAC address.

    memcpy (src_mac, ifr.ifr_hwaddr.sa_data, 6);



    // Report source MAC address to stdout.

    printf ("MAC address for interface %s is ", interface);

    for (i=0; i<5; i++) {

        printf ("%02x:", src_mac[i]);

    }

    printf ("%02x\n", src_mac[5]);



    // Find interface index from interface name and store index in

    // struct sockaddr_ll device, which will be used as an argument of sendto().

    memset (&device, 0, sizeof (device));

    if ((device.sll_ifindex = if_nametoindex (interface)) == 0) {

        perror ("if_nametoindex() failed to obtain interface index ");

        exit (EXIT_FAILURE);

    }

    printf ("Index for interface %s is %i\n", interface, device.sll_ifindex);



    // Set destination MAC address: you need to fill these out

    dst_mac[0] = 0x10;//设置目的网卡地址

    dst_mac[1] = 0x78;

    dst_mac[2] = 0xd2;

    dst_mac[3] = 0xc6;

    dst_mac[4] = 0x2f;

    dst_mac[5] = 0x89;



    // Fill out sockaddr_ll.

    device.sll_family = AF_PACKET;

    memcpy (device.sll_addr, src_mac, 6);

    device.sll_halen = htons (6);



    // 发送的data，长度能够随意，可是抓包时看到最小数据长度为46，这是以太网协议规定以太网帧数据域部分最小为46字节，不足的自己主动补零处理

    datalen = 12;

    data[0] = 'h';

    data[1] = 'e';

    data[2] = 'l';

    data[3] = 'l';

    data[4] = 'o';

    data[5] = ' ';

    data[6] = 'w';

    data[7] = 'o';

    data[8] = 'r';

    data[9] = 'l';

    data[10] = 'd';

    data[11] = '!';



    // Fill out ethernet frame header.

    frame_length = 6 + 6 + 2   + datalen;

    // Destination and Source MAC addresses

    memcpy (ether_frame, dst_mac, 6);

    memcpy (ether_frame + 6, src_mac, 6);



    ether_frame[12] = ETH_P_DEAN / 256;

    ether_frame[13] = ETH_P_DEAN % 256;



    // data

    memcpy (ether_frame + 14 , data, datalen);

    

    // Submit request for a raw socket descriptor.

    if ((sd = socket (PF_PACKET, SOCK_RAW, htons (ETH_P_ALL))) < 0) {//创建正真发送的socket

        perror ("socket() failed ");

        exit (EXIT_FAILURE);

    }

    // Send ethernet frame to socket.

    if ((bytes = sendto (sd, ether_frame, frame_length, 0, (struct sockaddr *) &device, sizeof (device))) <= 0) {

        perror ("sendto() failed");

        exit (EXIT_FAILURE);

    }

    printf ("send num=%d,read num=%d\n",frame_length,bytes);     

    // Close socket descriptor.

    close (sd);





    return (EXIT_SUCCESS);

}



抓包获取：

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下一章我们在Linux使用dev_add_pack加入此type的协议探測。

感谢David Buchan的网页提供的參考代码：

http://www.pdbuchan.com/rawsock/rawsock.html