用c语言写一个二层通信代码

以下是一个简单的使用 C 语言实现的二层通信代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#include <netinet/if_ether.h>
#include <netinet/in.h>
#include <unistd.h>

#define BUFFER_SIZE 65536

int main(int argc, char *argv[]) {
    int sock, length;
    struct sockaddr_in server_addr;
    char buffer[BUFFER_SIZE];

    // 创建原始套接字
    sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    if (sock < 0) {
        perror("socket() failed");
        exit(EXIT_FAILURE);
    }

    // 绑定网卡
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", "eth0");
    if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0) {
        perror("ioctl() failed");
        close(sock);
        exit(EXIT_FAILURE);
    }
    struct sockaddr_ll sll;
    memset(&sll, 0, sizeof(sll));
    sll.sll_family = AF_PACKET;
    sll.sll_ifindex = ifr.ifr_ifindex;
    sll.sll_protocol = htons(ETH_P_ALL);
    if (bind(sock, (struct sockaddr*) &sll, sizeof(sll)) < 0) {
        perror("bind() failed");
        close(sock);
        exit(EXIT_FAILURE);
    }

    // 接收数据帧并打印 MAC 地址
    while (1) {
        length = recv(sock, buffer, BUFFER_SIZE, 0);
        if (length < 0) {
            perror("recv() failed");
            close(sock);
            exit(EXIT_FAILURE);
        }
        struct ether_header *eth_hdr = (struct ether_header *) buffer;
        printf("Source: %02x:%02x:%02x:%02x:%02x:%02x\n",
               eth_hdr->ether_shost[0], eth_hdr->ether_shost[1],
               eth_hdr->ether_shost[2], eth_hdr->ether_shost[3],
               eth_hdr->ether_shost[4], eth_hdr->ether_shost[5]);
        printf("Destination: %02x:%02x:%02x:%02x:%02x:%02x\n",
               eth_hdr->ether_dhost[0], eth_hdr->ether_dhost[1],
               eth_hdr->ether_dhost[2], eth_hdr->ether_dhost[3],
               eth_hdr->ether_dhost[4], eth_hdr->ether_dhost[5]);
    }

    close(sock);
    return 0;
}

这个程序使用了 Linux 的原始套接字来接收二层数据帧，并打印出源 MAC 地址和目的 MAC 地址。需要注意的是，这个程序需要 root 权限才能运行，并且需要修改 `eth0` 为你的网卡名称。