c语言 arp报文发送程序

下面是一个简单的 C 语言 ARP 报文发送程序示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <net/if_arp.h>

#define ARP_REQUEST 1
#define ARP_REPLY 2

struct arp_packet {
    unsigned short hardware_type;
    unsigned short protocol_type;
    unsigned char hardware_size;
    unsigned char protocol_size;
    unsigned short opcode;
    unsigned char sender_mac[6];
    unsigned char sender_ip[4];
    unsigned char target_mac[6];
    unsigned char target_ip[4];
};

void get_mac_address(char *interface, unsigned char *mac) {
    struct ifreq ifr;
    int sock = socket(AF_INET, SOCK_DGRAM, 0);
    strcpy(ifr.ifr_name, interface);
    ioctl(sock, SIOCGIFHWADDR, &ifr);
    memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
    close(sock);
}

void get_ip_address(char *interface, unsigned char *ip) {
    struct ifreq ifr;
    int sock = socket(AF_INET, SOCK_DGRAM, 0);
    strcpy(ifr.ifr_name, interface);
    ioctl(sock, SIOCGIFADDR, &ifr);
    memcpy(ip, &((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr, 4);
    close(sock);
}

void send_arp_request(char *interface, char *target_ip) {
    int sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ARP));
    unsigned char source_mac[6];
    get_mac_address(interface, source_mac);
    unsigned char source_ip[4];
    get_ip_address(interface, source_ip);
    unsigned char broadcast_mac[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
    unsigned char target_ip_addr[4];
    inet_aton(target_ip, (struct in_addr *)target_ip_addr);
    struct arp_packet request;
    request.hardware_type = htons(ARPHRD_ETHER);
    request.protocol_type = htons(ETH_P_IP);
    request.hardware_size = 6;
    request.protocol_size = 4;
    request.opcode = htons(ARP_REQUEST);
    memcpy(request.sender_mac, source_mac, 6);
    memcpy(request.sender_ip, source_ip, 4);
    memset(request.target_mac, 0, 6);
    memcpy(request.target_ip, target_ip_addr, 4);
    struct sockaddr_ll socket_address;
    socket_address.sll_family = PF_PACKET;
    socket_address.sll_protocol = htons(ETH_P_ARP);
    socket_address.sll_ifindex = if_nametoindex(interface);
    socket_address.sll_hatype = ARPHRD_ETHER;
    socket_address.sll_pkttype = PACKET_BROADCAST;
    socket_address.sll_halen = ETH_ALEN;
    memcpy(socket_address.sll_addr, broadcast_mac, 6);
    sendto(sock, &request, sizeof(request), 0, (struct sockaddr *)&socket_address, sizeof(socket_address));
    close(sock);
}

int main(int argc, char **argv) {
    if (argc != 3) {
        printf("Usage: %s <interface> <target_ip>\n", argv[0]);
        return 1;
    }
    send_arp_request(argv[1], argv[2]);
    printf("ARP request sent to %s\n", argv[2]);
    return 0;
}

这个程序使用了 Linux 下的原始套接字接口和 ioctl 函数来获取本机的 MAC 地址和 IP 地址，并利用这些信息构造并发送了一个 ARP 请求报文。需要注意的是，发送 ARP 报文需要有 root 权限。