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一 实战前准备
1 准备两台虚拟机
A机配置
| 网卡 |
IP |
MAC |
| enp0s3 |
192.168.0.110 |
08:00:27:60:7b:7f |
| enp0s8 |
192.168.0.104 |
08:00:27:87:45:35 |
B机配置
| 网卡 |
IP |
MAC |
| enp0s3 |
192.168.0.120 |
08:00:27:0c:3b:d3 |
二 接收端
1 代码
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <sys/ioctl.h>
#include <arpa/inet.h> //for htons
#include <netinet/if_ether.h> //for ethhdr
#define LEN 60
void print_str16(unsigned char buf[], size_t len)
{
int i;
unsigned char c;
if (buf == NULL || len <= 0)
return;
for (i = 0; i < len; i++) {
c = buf[i];
printf("%02x", c);
}
printf("\n");
}
void print_sockaddr_ll(struct sockaddr_ll *sa)
{
if (sa == NULL)
return;
printf("sll_family:%d\n", sa->sll_family);
printf("sll_protocol:%#x\n", ntohs(sa->sll_protocol));
printf("sll_ifindex:%#x\n", sa->sll_ifindex);
printf("sll_hatype:%d\n", sa->sll_hatype);
printf("sll_pkttype:%d\n", sa->sll_pkttype);
printf("sll_halen:%d\n", sa->sll_halen);
printf("sll_addr:"); print_str16(sa->sll_addr, sa->sll_halen);
}
int main()
{
int result = 0, fd, n, count = 0;
char buf[LEN];
struct sockaddr_ll sa_recv;
struct ifreq ifr;
socklen_t sa_len = 0;
//char if_name[] = "eno16777736";
struct ethhdr *eth; //定义以太网头结构体指针
//创建套接字，自定义协议0x8902
fd = socket(PF_PACKET, SOCK_RAW, htons(0x8902));
if (fd < 0) {
perror("socket error\n");
return errno;
}
// 开始等待接收数据
while (1) {
memset(buf, 0, sizeof(buf));
// 第5个和第6个参数没有用NULL，这样可以获得对端（发送端）的物理地址sockaddr_ll的内容
n = recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *)&sa_recv, &sa_len);
//n = recvfrom(fd, buf, sizeof(buf), 0, NULL, NULL); //如果不需要打印sa_recv内容，用NULL也可以
if (n < 0) {
printf("sendto error, %d\n", errno);
return errno;
}
printf("******************* recvfrom msg %d ****************\n", ++count);
print_str16((unsigned char*)buf, n); //打印数据帧的内容
eth = (struct ethhdr*)buf;
//从eth里提取目的mac、源mac、协议号
printf("proto=0x%04x,dst mac addr:%02x:%02x:%02x:%02x:%02x:%02x\n", ntohs(eth->h_proto), eth->h_dest[0], eth->h_dest[1], eth->h_dest[2], eth->h_dest[3], eth->h_dest[4], eth->h_dest[5]);
printf("proto=0x%04x,src mac addr:%02x:%02x:%02x:%02x:%02x:%02x\n", ntohs(eth->h_proto), eth->h_source[0], eth->h_source[1], eth->h_source[2], eth->h_source[3], eth->h_source[4], eth->h_source[5]);
// 打印sockaddr_ll的内容
print_sockaddr_ll(&sa_recv);
printf("sa_len:%d\n", sa_len);
}
return 0;
}2 编译并运行
[root@localhost test]# g++ recv.cpp -o recv
[root@localhost test]# ./recv三 发送端
1 代码
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netpacket/packet.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <sys/ioctl.h>
#include <arpa/inet.h> //for htons
#define LEN 60
void print_str16(unsigned char buf[], size_t len)
{
int i;
unsigned char c;
if (buf == NULL || len <= 0)
return;
for (i = 0; i < len; i++) {
c = buf[i];
printf("%02x", c);
}
printf("\n");
}
int main()
{
int result = 0;
int fd, n, count = 3, nsend = 0; //count表示发送3个数据包
char buf[LEN];
struct sockaddr_ll sa;
struct ifreq ifr;
char if_name[] = "enp0s3"; //本机要发送数据的网卡名称
//对应enp0s3 ，192.168.0.110的网卡
char dst_mac[6] = { 0x08,0x00,0x27,0x60,0x7b,0x7f };
char src_mac[6];
short type = htons(0x8902);
memset(&sa, 0, sizeof(struct sockaddr_ll));
memset(buf, 0, sizeof(buf));
//创建套接字
fd = socket(PF_PACKET, SOCK_RAW, htons(0x8902));
if (fd < 0) {
printf("socket error, %d\n", errno);
return errno;
}
//获得网卡索引号
strcpy(ifr.ifr_name, if_name);
result = ioctl(fd, SIOCGIFINDEX, &ifr);
if (result != 0) {
printf("get mac index error, %d\n", errno);
return errno;
}
sa.sll_ifindex = ifr.ifr_ifindex; //赋值给物理层地址
//得到源MAC地址，即本机要发送数据的网卡MAC地址
result = ioctl(fd, SIOCGIFHWADDR, &ifr);
if (result != 0) {
printf("get mac addr error, %d\n", errno);
return errno;
}
memcpy(src_mac, ifr.ifr_hwaddr.sa_data, 6);
//设置数据给以太网帧头
memcpy(buf, dst_mac, 6);
memcpy(buf + 6, src_mac, 6);
memcpy(buf + 12, &type, 2);
print_str16((unsigned char*)buf, sizeof(buf)); //打印发要送的数据帧
//准备发送数据
while (count-- > 0) {
n = sendto(fd, buf, sizeof(buf), 0, (struct sockaddr *)&sa, sizeof(struct sockaddr_ll));
if (n < 0) {
printf("sendto error, %d\n", errno);
return errno;
}
printf("sendto msg %d, len %d\n", ++nsend, n);
}
return 0;
}2 编译并运行
[root@localhost test]# ./send
080027607b7f0800270c3bd3890200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
sendto msg 1, len 60
sendto msg 2, len 60
sendto msg 3, len 60此时接收端收到结果如下：
[root@localhost test]# ./recv
******************* recvfrom msg 1 ****************
080027607b7f0800270c3bd3890200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
proto=0x8902,dst mac addr:08:00:27:60:7b:7f
proto=0x8902,src mac addr:08:00:27:0c:3b:d3
sll_family:0
sll_protocol:0
sll_ifindex:0
sll_hatype:0
sll_pkttype:0
sll_halen:0
sll_addr:sa_len:18
******************* recvfrom msg 2 ****************
080027607b7f0800270c3bd3890200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
proto=0x8902,dst mac addr:08:00:27:60:7b:7f
proto=0x8902,src mac addr:08:00:27:0c:3b:d3
sll_family:17
sll_protocol:0x8902
sll_ifindex:0x2
sll_hatype:1
sll_pkttype:0
sll_halen:6
sll_addr:0800270c3bd3
sa_len:18
******************* recvfrom msg 3 ****************
080027607b7f0800270c3bd3890200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
proto=0x8902,dst mac addr:08:00:27:60:7b:7f
proto=0x8902,src mac addr:08:00:27:0c:3b:d3
sll_family:17
sll_protocol:0x8902
sll_ifindex:0x2
sll_hatype:1
sll_pkttype:0
sll_halen:6
sll_addr:0800270c3bd3
sa_len:18四 说明
默认情况下，从任何接口收到符合指定协议（包括自定义协议号）的所有数据报文都会被传送到原始PACKET套接口，而使用bind系统调用并以一个sockaddr_ll结构体对象将PACKET套接口与某个网络接口相绑定，可以使我们的PACKET原始套接字只接收指定接口的数据报文。