linux eth_p_ip

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <linux/if_packet.h>

#define BUF_SIZE 65536

int main() {
    int sockfd;
    struct sockaddr_ll sa;
    char buffer[BUF_SIZE];

    sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_IP));
    if (sockfd < 0) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    memset(&sa, 0, sizeof(sa));
    sa.sll_family = AF_PACKET;
    sa.sll_protocol = htons(ETH_P_IP);
    sa.sll_ifindex = if_nametoindex("eth0"); // 替换为实际的网络接口名称

    if (bind(sockfd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
        perror("bind");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    while (1) {
        ssize_t len = recvfrom(sockfd, buffer, BUF_SIZE, 0, NULL, NULL);
        if (len < 0) {
            perror("recvfrom");
            break;
        }
        printf("Received IPv4 packet of length %zd\n", len);
    }

    close(sockfd);
    return 0;
}