用libcap实现发包
时间: 2024-05-06 09:20:18 浏览: 18
Libcap是一个库,用于在Linux中访问网络接口。可以使用libcap库来发送和捕获网络数据包。下面是一个简单的例子,用于使用libcap库发送一个基本的UDP数据包。
首先,需要安装libcap库。在Ubuntu系统上,可以使用以下命令进行安装:
```
sudo apt-get install libcap-dev
```
接下来,创建一个名为send_packet.c的文件,并添加以下代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <netinet/if_ether.h>
#include <net/if.h>
#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <linux/filter.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/ip.h>
#define SRC_IP "192.168.1.1"
#define DEST_IP "192.168.1.2"
#define SRC_PORT 1234
#define DEST_PORT 5678
#define DATA "Hello, world!"
/* UDP packet structure */
struct udp_packet {
struct udphdr udp_header;
char data[1024];
};
/* IP header checksum calculation */
unsigned short checksum(unsigned short *ptr, int length) {
unsigned int sum = 0;
for (sum = 0; length > 1; length -= 2) {
sum += *ptr++;
}
if (length == 1) {
sum += *(unsigned char*)ptr;
}
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
return ~sum;
}
int main() {
int sockfd;
struct sockaddr_ll socket_address;
int ifindex;
struct ifreq ifr;
struct iphdr *iph;
struct udphdr *udph;
struct udp_packet packet;
int packet_size;
char *interface_name = "eth0";
char *src_ip = SRC_IP;
char *dest_ip = DEST_IP;
int src_port = SRC_PORT;
int dest_port = DEST_PORT;
/* Open socket */
sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_IP));
if (sockfd == -1) {
perror("socket");
exit(EXIT_FAILURE);
}
/* Get interface index */
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, interface_name, IFNAMSIZ-1);
if (ioctl(sockfd, SIOCGIFINDEX, &ifr) == -1) {
perror("ioctl");
exit(EXIT_FAILURE);
}
ifindex = ifr.ifr_ifindex;
/* Bind socket to interface */
memset(&socket_address, 0, sizeof(socket_address));
socket_address.sll_family = AF_PACKET;
socket_address.sll_ifindex = ifindex;
socket_address.sll_protocol = htons(ETH_P_IP);
if (bind(sockfd, (struct sockaddr*)&socket_address, sizeof(socket_address)) == -1) {
perror("bind");
exit(EXIT_FAILURE);
}
/* Prepare IP header */
iph = (struct iphdr*)&packet;
iph->ihl = 5;
iph->version = 4;
iph->tos = 0;
iph->id = htons(54321);
iph->frag_off = htons(0);
iph->ttl = 255;
iph->protocol = IPPROTO_UDP;
iph->saddr = inet_addr(src_ip);
iph->daddr = inet_addr(dest_ip);
iph->tot_len = htons(sizeof(struct iphdr) + sizeof(struct udphdr) + strlen(DATA));
iph->check = checksum((unsigned short*)iph, sizeof(struct iphdr));
/* Prepare UDP header */
udph = (struct udphdr*)((char*)iph + sizeof(struct iphdr));
udph->source = htons(src_port);
udph->dest = htons(dest_port);
udph->len = htons(sizeof(struct udphdr) + strlen(DATA));
udph->check = 0;
/* Prepare UDP data */
memcpy(packet.data, DATA, strlen(DATA));
/* Send packet */
packet_size = sizeof(struct iphdr) + sizeof(struct udphdr) + strlen(DATA);
if (sendto(sockfd, &packet, packet_size, 0, (struct sockaddr*)&socket_address, sizeof(socket_address)) == -1) {
perror("sendto");
exit(EXIT_FAILURE);
}
printf("Packet sent successfully.\n");
close(sockfd);
return 0;
}
```
在上面的代码中,我们使用了Linux的原始套接字来发送一个UDP数据包。我们首先打开一个原始套接字,然后将其绑定到一个特定的网络接口上。然后,我们构造一个UDP数据包,将其放置在一个IP数据包中,并将其发送到目标主机。
在本例中,我们使用了eth0作为网络接口,并将数据包发送到192.168.1.2的5678端口。我们使用了数据“Hello, world!”作为UDP数据。
编译和运行上述代码:
```
gcc -o send_packet send_packet.c -lcap
sudo ./send_packet
```
这将发送一个UDP数据包到目标主机,并在控制台上输出“Packet sent successfully.”。
请注意,在Linux中,必须以root权限运行程序才能使用原始套接字。