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
", 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
", 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
",frame_length,bytes);
// Close socket descriptor.
close (sd);
return (EXIT_SUCCESS);
}
抓包获取：
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