ioctl 命令

缺乏、安全感 2022-05-17 05:04 202阅读 0赞

**引言**

文件描述符是低层的输入和输出接口。描述符可以表示到设备、管道或套接字的连接，这些连接用于与另一个进程或普通文件进行通信。*I/O 控制* (ioctl) 函数调用可以用来对特殊文件的基础设备参数进行操作。它们可以完成与打开的文件描述符相关联的控制功能。这些命令涉及文件、流、普通数据链路控制以及其他各种设备。

本文将讨论 AIX® Version 5.3 中提供的与网络操作和套接字相关的命令。在下列文件中列出了与套接字相关的命令和结构：

*  `sys/ioctl.h`
 *  `net/if_arp.h`
 *  `net/if.h`
 *  `net/netopt.h`
 *  `netinet/in.h`

应用程序开发人员可以使用这些命令，并且在 AIX Version 5.3 的文档中对这些命令进行了详细的描述。本文说明了有关 Internet Protocol Version 6 (IPv6) 地址和 Internet Protocol Version 4 (IPv4) 堆栈的常用命令的典型用法。

**使用 ioctl 套接字控制选项**

通常，网络程序需要了解系统中所有有关网络接口和 IP 地址的可用信息。现在，未来的应用程序可以支持 IPv4 和 IPv6 双协议栈。ioctl 结构需要对指针进行遍历和操作，以处理 IPv4 和 IPv6 地址在长度上的差别（除了使用合适的套接字结构 sockaddr\_in6 或 sockaddr\_storage 之外）。

AIX Version 5.3 提供了很多 ioctl 套接字控制选项，以提取各种有关网络接口的信息。这些 ioctl 命令用于查询接口的状态并对其属性进行操作。下面的部分中包含了一些有用的命令的代码段。有关 ioctl 命令的完整列表，请参见[参考资料][Link 1]部分。

**ioctl 命令所使用的结构**

下面的清单介绍了一些最重要的结构，使用 ioctl 套接字命令时常常用到这些结构。

**清单 1. struct ifreq (/usr/include/net/if.h)**

<table style="font-size:0.8em; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
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   <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:2px; padding-right:2px; padding-bottom:5px; padding-left:2px"> <pre style="width:694px; margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">				
/* Interface request structure used for socket
 * ioctl's.  All interface ioctl's must have parameter
 * definitions which begin with ifr_name.  The
 * remainder may be interface specific.
 */
struct  ifreq {
#ifndef IFNAMSIZ
#define IFNAMSIZ        16
#endif
        char    ifr_name[IFNAMSIZ]; 
        union {
                struct  sockaddr ifru_addr;
                struct  sockaddr ifru_dstaddr;
                struct  sockaddr ifru_broadaddr;
                __ulong32_t     ifru_flags;
                int     ifru_metric;
                caddr_t ifru_data;
                u_short ifru_site6;
                __ulong32_t   ifru_mtu;
                int     ifru_baudrate;
        } ifr_ifru;

<strong>Following macros are provided for convenience</strong>

#define ifr_addr        ifr_ifru.ifru_addr      /* address */
#define ifr_dstaddr     ifr_ifru.ifru_dstaddr   /* other end of p-to-p link */
#define ifr_broadaddr   ifr_ifru.ifru_broadaddr /* broadcast address */
#define ifr_flags       ifr_ifru.ifru_flags     /* flags */
#define ifr_metric      ifr_ifru.ifru_metric    /* metric */
#define ifr_data        ifr_ifru.ifru_data      /* for use by interface */
#define ifr_site6       ifr_ifru.ifru_site6     /* IPv6 site index */
#define ifr_mtu         ifr_ifru.ifru_mtu       /* mtu of interface */
#define ifr_isno        ifr_ifru.ifru_data      /* pointer to if_netopts */
#define ifr_baudrate    ifr_ifru.ifru_baudrate  /* baudrate of interface */
};
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

**清单 2. struct ifconf (/usr/include/net/if.h)**

<strong>Following macros are provided for convenience</strong>

#define ifc_buf ifc_ifcu.ifcu_buf       /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req       /* array of structures returned */
};
      </pre> </td> 
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[回页首][Link 2]

**代码示例**

下面的[表 1][1] 介绍了一些接口检索命令。该信息来源于 IBM System p™ 和 AIX。

**表 1. 接口检索命令 **

<table style="font-size:0.8em; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); border-top-width:0px; border-top-style:initial; border-top-color:initial; margin-bottom:8px; width:708px; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> ioctl 命令</th> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> 描述</th> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGSIZIFCONF" style="color:rgb(153,102,153)" rel="nofollow">SIOCGSIZIFCONF</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> 获得获取 SIOCGIFCONF 返回的所有接口的配置信息所需的内存。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">		
ioctl(fd, SIOCGSIZIFCONF, (caddr_t)&amp;ifconfsize);

int ifconfsize;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> </td> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGIFADDR" style="color:rgb(153,102,153)" rel="nofollow">SIOCGIFADDR<br> <br> SIOCSIFADDR</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> SIOCGIFADDR 获取接口地址，而 SIOCSIFADDR 设置接口地址。<code style="font-size:small!important">ifr.ifr_addr</code>&nbsp;字段返回地址。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, SIOCGIFADDR, (caddr_t)&amp;ifr, sizeof(struct ifreq));

ioctl(fd, SIOCSIFADDR, (caddr_t)&amp;ifr, sizeof(struct ifreq));

struct ifreq ifr;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> </td> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGIFCONF" style="color:rgb(153,102,153)" rel="nofollow">SIOCGIFCONF</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> 返回系统中配置的所有接口的配置信息。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, SIOCGIFCONF, (caddr_t)&amp;ifc);

struct ifconf ifconf;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> </td> 
  </tr> 
 </tbody> 
</table>

**SIOCGSIZIFCONF**

下面的代码段可以获取用来填充所有配置接口的信息所需的缓冲区大小。

**清单 3. 使用 SIOCGSIZIFCONF 获得所需的缓冲区大小**

main
{
    struct ifconf ifc;
    int sd;
    sd=socket(AF_INET6,SOCK_DGRAM,0);
    printf("Size of memory needed = %d\n",get_interface_size(sd));
}
 
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

上面代码的输出是：

**SIOCGIFCONF 和 SIOCGIFADDR**

SIOCGIFCONF 和 SIOCGIFADDR 命令可以用来检索接口的地址。SIOCGIFCONF 可以用来获取所有配置接口的信息，SIOCGIFADDR 可以用来检索特定接口的地址。

**清单 4. 使用 SIOCGIFCONF 获取配置信息**

<table style="font-size:0.8em; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
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  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:2px; padding-right:2px; padding-bottom:5px; padding-left:2px"> <pre style="width:694px; margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">					
/*This function uses loops to find out buffer size instead of SIOCGSIZIFCONF 
  allocates the buffer and gets the information list*/
int alloc_buffer_size(int sd,struct ifconf *ifc){
    int ret=-1,bsz=sizeof(struct ifreq);
    int prevsz=bsz;
    ifc-&gt;ifc_req=NULL;
    ifc-&gt;ifc_len=bsz;
    do{
       ifc-&gt;ifc_req=(struct ifreq *)realloc(ifc-&gt;ifc_req,bsz);
       if(!ifc-&gt;ifc_req){
         perror("Malloc failed :");
         return ret;
       }
       ifc-&gt;ifc_len=bsz;
       ret=ioctl(sd,SIOCGIFCONF,(caddr_t)ifc);
       if(ret==-1){
          perror("Error getting size of interface :");
          return ret;
       }
      if(prevsz==ifc-&gt;ifc_len)
        break;
      else{
         bsz*=2;
         prevsz=(0==ifc-&gt;ifc_len ? bsz : ifc-&gt;ifc_len) ;
      }
    }while(1);
    ifc-&gt;ifc_req=(struct ifreq *)realloc(ifc-&gt;ifc_req,prevsz);
    return ifc-&gt;ifc_len;
}

</pre> </td> 
  </tr> 
 </tbody> 
</table>

在使用 `ifreq` 结构中的配置信息填充了列表之后，可以对其进行遍历以检索所需的数据。根据调用之后该结构中填充的套接字地址的长度，可以对这个指针进行移动。下面的[清单 5][5] 显示了上面代码的列表中获得的系统中可用的 IP。

**清单 5. 从配置列表中检索信息**

/* This function prints all the configured IPs on the
 * system given the ifconf structure allocated previously*/
void print_ips(struct ifconf *ifc){
     char *cp,*cplim,addr[INET6_ADDRSTRLEN];
     struct ifreq *ifr=ifc-&gt;ifc_req;
     cp=(char *)ifc-&gt;ifc_req;
     cplim=cp+ifc-&gt;ifc_len;
     for(;cp&lt;cplim;cp+=(sizeof(ifr-&gt;ifr_name) + SIZE(ifr-&gt;ifr_addr))){
        /* NOTE: You cannot just increment cp with sizeof(struct ifreq)
         * as structures returned are of different length.
         */
        ifr=(struct ifreq *)cp;
        printf("%s :",ifr-&gt;ifr_name);
        getip(ifr,addr);
        printf("%s\n",addr);
     }
      return ;
}
main
{
    struct ifconf ifc;
    int sd;
    sd=socket(AF_INET6,SOCK_DGRAM,0);
    alloc_buffer_size(sd,&amp;ifc);
    print_ips(&amp;ifc);
}
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

上面代码的输出是：

**清单 6. 使用 SIOCGIFADDR 获取接口地址**

<table style="font-size:0.8em; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:2px; padding-right:2px; padding-bottom:5px; padding-left:2px"> <pre style="width:694px; margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">					
/* Given a ifreq structure this function returns its IP address */
void getip(struct ifreq *ifr,char *addr){
  struct sockaddr *sa;
  sa=(struct sockaddr *)&amp;(ifr-&gt;ifr_addr);
  switch(sa-&gt;sa_family){
    case AF_INET6:
      inet_ntop(AF_INET6,(struct in6_addr *)&amp;(((struct sockaddr_in6 *)sa)-&gt;sin6_addr),
         addr,INET6_ADDRSTRLEN);
      break;
    default : strcpy(addr,inet_ntoa(((struct sockaddr_in *)sa)-&gt;sin_addr));
    }
   return;
}

main
{
  char netaddr[INET_ADDRSTRLEN];
  int sd;
  sd=socket(AF_INET,SOCK_DGRAM,0);
  strcpy(ifr.ifr_name,"en0");
  if((ioctl(sd,SIOCGIFADDR,(caddr_t)&amp;ifr,sizeof(struct ifreq)))&lt;0)
     perror("Error : ");
  getip(&amp;ifr,netaddr);
  printf("%s\n",netaddr);
}
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

上面代码的输出是：

下面的[表 2][2] 介绍了接口标志和一些属性检索命令。

**表 2. 接口标志和属性检索命令**

<table style="font-size:0.8em; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); border-top-width:0px; border-top-style:initial; border-top-color:initial; margin-bottom:8px; width:708px; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> ioctl 命令</th> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> 描述</th> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGIFFLAGS" style="color:rgb(153,102,153)" rel="nofollow">SIOCGIFFLAGS</a>&nbsp;<br> <br> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCSIFFLAGS" style="color:rgb(153,102,153)" rel="nofollow">SIOCSIFFLAGS</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> SIOCGIFFLAGS 可以获取接口标志。 <p style="margin-top:0px; margin-bottom:0px; padding-top:0.3em; padding-right:5px; padding-bottom:0.7em; padding-left:5px; font-size:1em"> SIOCSIFFLAGS 可以设置接口标志。</p> 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, cmd, (caddr_t)&amp;ifr);
struct ifreq ifr;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> </td> 
  </tr> 
 </tbody> 
</table>

**SIOCGIFFLAGS**

在使用 [SIOCGIFCONF][] 获取了接口列表之后，您可以使用 SIOCGIFFLAGS-SIOCSIFFLAGS 对来获取和设置接口的属性。接口标志表示为 IFF\_XXX。有关完整的列表，请参阅文件 /usr/include/net/if.h。

下面的示例使用一对接口标志来检索其当前状态，并检查环回。也可以使用其他选项。

**清单 7. 验证接口的状态和类型**

<table style="font-size:0.8em; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:2px; padding-right:2px; padding-bottom:5px; padding-left:2px"> <pre style="width:694px; margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">				
   for(;cp&lt;cplim;){
        ifr=(struct ifreq *)cp;
        cp+=(sizeof(ifr-&gt;ifr_name) + SIZE(ifr-&gt;ifr_addr));
        printf("%-9s  ",ifr-&gt;ifr_name);
        ret=ioctl(sd,SIOCGIFFLAGS,(caddr_t)ifr);
        if(ret==-1){
          perror("Error getting flags for interface :");
          return ;
        }
        if((ifr-&gt;ifr_flags)&amp;IFF_UP)
           printf("UP");
        else printf("DOWN");
        if((ifr-&gt;ifr_flags)&amp;IFF_LOOPBACK)
           printf(",Loopback");
	printf("\n");
     }
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

上面代码的输出是：

**清单 8. 设置接口标志**

sit0: flags=4900041&lt;UP,RUNNING,LINK0,64BIT&gt;
        inet6 ::9.182.192.169/96

<strong>Code to set the interface flag </strong>

int set_interface_flag(int sd,short flag,char *interface){
    struct ifreq ifr;
    int oldflags;
    strcpy(ifr.ifr_name,interface);
    if((ioctl(sd,SIOCGIFFLAGS,(caddr_t)&amp;ifr))==-1){
      perror("Error getting interface flags :");
      return -1;
    }
    printf("Setting new interface flag 0X%x\n",flag);
    ifr.ifr_flags|=flag;
    if((ioctl(sd,SIOCSIFFLAGS,(caddr_t)&amp;ifr))==-1){
      perror("Error setting interface flags :");
      return -1;
    }
    return 0;
}

main
{
    int sd;
    sd=socket(AF_INET6,SOCK_DGRAM,0);
    set_interface_flag(sd,IFF_NOTRAILERS,"sit0");
}
</pre> </td> 
  </tr> 
 </tbody> 
</table>

上面代码的输出是：

$./myprog
Setting new interface flag 0X20

$ifconfig -a
.............
.............
sit0: flags=4900061&lt;UP,<strong>NOTRAILERS</strong>,RUNNING,LINK0,64BIT&gt;
        inet6 ::9.182.192.169/96
.............
.............
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

[表 3][3] 介绍了一些用于网络优化的命令。

**表 3. 用于网络优化的命令**

<table style="font-size:0.8em; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); border-top-width:0px; border-top-style:initial; border-top-color:initial; margin-bottom:8px; width:708px; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> ioctl 命令</th> 
   <th style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; background-color:rgb(247,248,252); font-size:0.7em"> 描述</th> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGIFMTU" style="color:rgb(153,102,153)" rel="nofollow">SIOCGIFMTU</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> SIOCGIFMTU 可以获取接口的最大传输单元 (MTU)。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, cmd, (caddr_t)&amp;ifr);

struct ifreq ifr;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> 这个 MTU 值存储在&nbsp;<code style="font-size:small!important">ifr.ifr_mtu</code>&nbsp;字段中。</td> 
  </tr> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGNETOPT1" style="color:rgb(153,102,153)" rel="nofollow">SIOCGNETOPT</a>&nbsp;<br> <a href="http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGNETOPT1" style="color:rgb(153,102,153)" rel="nofollow">SIOCGNETOPT1</a></td> 
   <td style="font-family:arial,nsimsun,sans-serif; border-top-color:rgb(204,204,204); border-top-style:solid; border-top-width:1px; padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:0.7em"> SIOCGNETOPT 可以获取一个网络选项的值。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, cmd, (caddr_t)&amp;oreq);
struct optreq oreq;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> SIOCGNETOPT1 可以获取当前值、缺省值和网络选项的范围。 
    <table style="font-size:0.8em"> 
     <tbody> 
      <tr> 
       <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:8px; padding-right:5px; padding-bottom:8px; padding-left:5px; vertical-align:top; font-size:1em"> <pre style="margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">ioctl(fd, SIOCGNETOPT1, (caddr_t)&amp;oreq);
struct optreq1 oreq;</pre> </td> 
      </tr> 
     </tbody> 
    </table> <br> </td> 
  </tr> 
 </tbody> 
</table>

**SIOCGIFMTU**

**清单 9. 从 ifreq 结构获取 MTU**

**SIOCGNETOPT1**

SIOCGNETOPT1 给出当前值、缺省值和网络选项的范围。

**清单 10. 从 optreq1 结构获取网络选项**

上面代码的输出是：

在 AIX 中，您还可以使用 `no` 命令来管理各种网络优化参数。有关更详细的信息，请参阅相应的 man 页面。

**清单 11. AIX 计算机上“no”命令的输出**

<table style="font-size:0.8em; color:rgb(0,0,0); font-family:Simsun; text-align:left"> 
 <tbody> 
  <tr> 
   <td style="font-family:arial,nsimsun,sans-serif; background-color:rgb(247,247,247)!important; border-top-width:1px; border-right-width:1px; border-bottom-width:1px; border-left-width:1px; border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid; border-top-color:rgb(204,204,204); border-right-color:rgb(204,204,204); border-bottom-color:rgb(204,204,204); border-left-color:rgb(204,204,204); padding-top:2px; padding-right:2px; padding-bottom:5px; padding-left:2px"> <pre style="width:694px; margin-top:0px; margin-bottom:0px; font-family:'Andale Mono','Lucida Console',Monaco,Liberation,fixed,monospace; font-size:11px; overflow-x:auto; overflow-y:auto; background-color:rgb(247,247,247)!important">				
$&gt; no -a|more
               arpqsize = 12
               arpt_killc = 20
              arptab_bsiz = 7
                arptab_nb = 149
                bcastping = 0
      clean_partial_conns = 0
                 delayack = 0
            delayackports = {}
         dgd_packets_lost = 3
            dgd_ping_time = 5
           dgd_retry_time = 5
       directed_broadcast = 0
         extendednetstats = 0
                 fasttimo = 200
........
........
      </pre> </td> 
  </tr> 
 </tbody> 
</table>

[回页首][Link 2]

**总结**

ioctl 命令的功能非常强大，您可以使用它们来访问或修改网络（或其他）设备的可配置参数。它们使用了各种各样的数据结构，应该使用正确的数据来填充这些数据结构，以便实现预期的结果。您将发现在使用 AF\_INET 和 AF\_INET6 系列时存在的区别。本文提供了一小部分常用命令子集的代码示例。要获得 AIX Version 5.3 中完整的命令清单，请转到[参考资料][Link 1]部分。我们希望这些关于 ioctl 的信息对您有用。

[Link 1]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#resources
[Link 2]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#ibm-pcon
[1]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#table1
[5]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#listing5
[2]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#table2
[SIOCGIFCONF]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#SIOCGIFCONF
[3]: http://www.ibm.com/developerworks/cn/aix/library/au-ioctl-socket.html#table3