ioctl在socket中的一些用法及示例

時間 2019-11-20

原文原文鏈接

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

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函數 : ioctl(int fd, int request, void * arg)
定義 : <sys/ioctl.h>
功能 : 控制I/O設備, 提供了一種得到設備信息和向設備發送控制參數的手段.
參數 : int fd      文件句柄. 用於socket時, 是socket套接字.
       int request 函數定義的全部操做. 關於socket的操做, 定義在<linux/sockios.h>文件中.
       void *arg    指針的類型依賴於request參數.

如下表格從網上收集了request - arg指針類型的對應關係

類別html	Requestlinux	說明ios	數據類型緩存
套接口異步	SIOCATMARK SIOCSPGRP SIOCGPGRPsocket	是否位於帶外標記設置套接口的進程ID 或進程組ID 獲取套接口的進程ID 或進程組ID函數	int int intui
文件spa	FIONBIN FIOASYNC FIONREAD FIOSETOWN FIOGETOWN.net	設置/ 清除非阻塞I/O 標誌設置/ 清除信號驅動異步I/O 標誌獲取接收緩存區中的字節數設置文件的進程ID 或進程組ID 獲取文件的進程ID 或進程組ID	int int int int int
接口	SIOCGIFCONF SIOCSIFADDR SIOCGIFADDR SIOCSIFFLAGS SIOCGIFFLAGS SIOCSIFDSTADDR SIOCGIFDSTADDR SIOCGIFBRDADDR SIOCSIFBRDADDR SIOCGIFNETMASK SIOCSIFNETMASK SIOCGIFMETRIC SIOCSIFMETRIC SIOCGIFMTU SIOCxxx	獲取全部接口的清單設置接口地址獲取接口地址設置接口標誌獲取接口標誌設置點到點地址獲取點到點地址獲取廣播地址設置廣播地址獲取子網掩碼設置子網掩碼獲取接口的測度設置接口的測度獲取接口MTU （還有不少取決於系統的實現）	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	建立/ 修改ARP 表項獲取ARP 表項刪除ARP 表項	struct arpreq struct arpreq struct arpreq
路由	SIOCADDRT SIOCDELRT	增長路徑刪除路徑	struct rtentry struct rtentry
流	I_xxx

socket最經常使用到的結構體: struct ifreq 定義在<net/if.h>.(包括struct ifconf/ifr_flags等的定義)

1、獲取

如下例程經過ioctl獲取設備"eth0"的IP/掩碼/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);
}

2、設置

如下例程設置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
}

屏蔽的代碼用於設置IP後, 激活新設置. 多數系統不須要這步操做.
並且這步僅做演示. 真實使用的時候, 至少應該
1. 獲取當前ifr.ifr_flags
2. ifr.ifr_flags |= IFF_UP;

以上是ioctl的一些示例, 實戰中靈活使用、觸類旁通.