C/C++详解实现二层转发

void ethping(char *destination, char* interface){
    //创建原始套接字。 指定接口名称
    struct RawSocket* rawsocket = new_RawSocket(interface);
    //数据包数据缓冲区
    unsigned char buf[1024];
    //定义数据包。 投射以匹配以太网帧的格式
    struct ethhdr_frame* eth_packet = (struct ethhdr_frame*)buf;
    //存储发送方和接收方的 MAC 地址。 协议类型是可选的，并且指定了 0x0806。
    //根据指定的接口名称获取发送者的MAC地址
    memset(buf, 0x0, sizeof(eth_packet));
    set_macaddr_from_string(destination, eth_packet->h_dest);
    set_macaddr_from_ifname(interface, eth_packet->h_source);
	eth_packet->h_proto = 0x0806;
    //在payload中设置字符串“Hello”
    char* data = "Hello";
    memcpy(eth_packet->payload, data, sizeof(data)); 
    //绑定指定接口上的socket
    rawsocket->bind_rawsocket(rawsocket);
    int send_size = send(rawsocket->socket, &buf, sizeof(buf), 0);
    printf("%dbyte send.\n", send_size);
    //关闭原始套接字
    rawsocket->close_rawsocket(rawsocket);
}
int main(int argc, char *argv[]){
    if(argc != 3){
        printf("usage: %s <destination> <interface>", argv[0]);
        exit(0);
    }
    char *destination = argv[1];
    char *if_name = argv[2];
    ethping(destination, if_name);
    return 0;
}

void start_daemon(char *interface){
    //创建原始套接字（指定接收器接口名称）
    struct RawSocket* rawsocket = new_RawSocket(interface);
    int len;
    //使用 bind 绑定到接口
    rawsocket->bind_rawsocket(rawsocket);
    while(1){
        int len = rawsocket->recv_rawsocket(rawsocket);
        struct ethhdr_frame *data = (struct ethhdr_frame*)(rawsocket->buf);
        fflush(stdout);
        //显示接收到的数据包的内容
        if(len > 0){
            printf("src: ");
            print_macaddr(data->h_source);
            printf(", ");
            printf("dst: ");
            print_macaddr(data->h_dest);
            printf(", ");
            printf("type: ");
            printf("%02x", (uint16_t)data->h_proto);
            printf(", ");
            printf("payload: ");
            printf("%s", data->payload);
            printf("\n");
        }
    }
}
int main(int argc, char *argv[]){
    if(argc != 2){
        printf("usage: %s <interface>", argv[0]);
        exit(0);
    }
    char *if_name = argv[1];
    start_daemon(if_name);
    return 0;
}