ioctl在socket中的一些用法和示例

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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}

屏蔽的代码用于设置IP后, 激活新设置. 多数系统不需要这步操作.
而且这步仅作演示. 真实使用的时候, 至少应该
1. 获取当前ifr.ifr_flags
2. ifr.ifr_flags |= IFF_UP;