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ioctl在socket中的一些用法及示例

原文： http://blog.chinaunix.net/uid-20692625-id-3172833.html

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函数 : ioctl(int fd, int request, void * arg)
定义 : <sys/ioctl.h>
功能 : 控制I/O设备, 提供了一种获得设备信息和向设备发送控制参数的手段.
参数 : int fd      文件句柄. 用于socket时, 是socket套接字.
       int request 函数定义的所有操作. 关于socket的操作, 定义在<linux/sockios.h>文件中.
       void *arg    指针的类型依赖于request参数.

以下表格从网上收集了request - arg指针类型的对应关系

类别	Request	说明	数据类型
套接口	SIOCATMARK SIOCSPGRP SIOCGPGRP	是否位于带外标记设置套接口的进程ID 或进程组ID 获取套接口的进程ID 或进程组ID	int int int
文件	FIONBIN FIOASYNC FIONREAD FIOSETOWN FIOGETOWN	设置/ 清除非阻塞I/O 标志设置/ 清除信号驱动异步I/O 标志获取接收缓存区中的字节数设置文件的进程ID 或进程组ID 获取文件的进程ID 或进程组ID	int int int int int
接口	SIOCGIFCONF SIOCSIFADDR SIOCGIFADDR SIOCSIFFLAGS SIOCGIFFLAGS SIOCSIFDSTADDR SIOCGIFDSTADDR SIOCGIFBRDADDR SIOCSIFBRDADDR SIOCGIFNETMASK SIOCSIFNETMASK SIOCGIFMETRIC SIOCSIFMETRIC SIOCGIFMTU SIOCxxx	获取所有接口的清单设置接口地址获取接口地址设置接口标志获取接口标志设置点到点地址获取点到点地址获取广播地址设置广播地址获取子网掩码设置子网掩码获取接口的测度设置接口的测度获取接口MTU （还有很多取决于系统的实现）	struct ifconf struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq struct ifreq
ARP	SIOCSARP SIOCGARP SIOCDARP	创建/ 修改ARP 表项获取ARP 表项删除ARP 表项	struct arpreq struct arpreq struct arpreq
路由	SIOCADDRT SIOCDELRT	增加路径删除路径	struct rtentry struct rtentry
流	I_xxx

socket最常用到的结构体: struct ifreq 定义在<net/if.h>.(包括struct ifconf/ifr_flags等的定义)

一、获取

以下例程通过ioctl获取设备"eth0"的IP/掩码/硬件址

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
 
#include "net/if.h"
#include "arpa/inet.h"
#include "linux/sockios.h"
 
int main(int argc,char *argv[])
{
    struct sockaddr_in *addr;
    struct ifreq ifr;
    char*address;
    int sockfd;
 
    char *name = "eth0";
    if( strlen(name) >= IFNAMSIZ)
        printf("device name is error.\n"), exit(0);
         
    strcpy( ifr.ifr_name, name);
         
    sockfd = socket(AF_INET,SOCK_DGRAM,0);
 
    //get inet addr
    if( ioctl( sockfd, SIOCGIFADDR, &ifr) == -1)
        printf("ioctl error.\n"), exit(0);
 
    addr = (struct sockaddr_in *)&(ifr.ifr_addr);
    address = inet_ntoa(addr->sin_addr);
 
    printf("inet addr: %s\n",address);
 
    //get Mask
    if( ioctl( sockfd, SIOCGIFNETMASK, &ifr) == -1)
        printf("ioctl error.\n"), exit(0);
 
    addr = (struct sockaddr_in *)&ifr.ifr_addr;
    address = inet_ntoa(addr->sin_addr);
 
    printf("Mask: %s\n",address);
 
    //get HWaddr 
    u_int8_t hd[6];
    if(ioctl(sockfd, SIOCGIFHWADDR, &ifr) == -1)
        printf("hwaddr error.\n"), exit(0);
 
    memcpy( hd, ifr.ifr_hwaddr.sa_data, sizeof(hd));
    printf("HWaddr: %02X:%02X:%02X:%02X:%02X:%02X\n", hd[0], hd[1], hd[2], hd[3], hd[4], hd[5]);
     
    exit(0);
}

二、设置

以下例程设置eth0的IP地址.

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
 
#include "net/if.h"
#include "arpa/inet.h"
#include "linux/sockios.h"
 
int main(int argc,char *argv[])
{
    char *dev = "eth0";
    char *ip = "192.168.1.252";
     
    struct ifreq ifr;
    if( strlen(dev) >= IFNAMSIZ)
        printf("device name error.\n"), exit(0);
    else
        strcpy( ifr.ifr_name, dev);
     
    int sockfd = socket(AF_INET,SOCK_DGRAM,0);
 
    //get inet addr
    if( ioctl( sockfd, SIOCGIFADDR, &ifr) == -1)
        printf("ioctl error.\n"), exit(0);
     
    struct sockaddr_in *addr = (struct sockaddr_in *)&(ifr.ifr_addr);
    char * address = inet_ntoa(addr->sin_addr);
 
    printf("current inet addr: %s\n",address);
 
    //set inet addr
    struct sockaddr_in *p = (struct sockaddr_in *)&(ifr.ifr_addr);
 
    p->sin_family = AF_INET;
    inet_aton( ip, &(p->sin_addr));
 
    if( ioctl( sockfd, SIOCSIFADDR, &ifr) == -1)
     printf("ioctl error.\n"), exit(0);
    else   
        printf("change inet addr to: %s\n", ip);
 
    //any OS need active dev.
    /*ifr.ifr_flags |= IFF_UP;
    if( ioctl( sockfd, SIOCSIFFLAGS, &ifr) == -1)
        printf("active fault.\n"), exit(0);
    else
        printf("%s[%s] is working...\n", dev, ip);
    */
         
    close(sockfd);
    exit(1);
    //end
}