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Linux 下 可以使用ioctl()函數 以及 結構體 struct ifreq 結構體struct ifconf來擷取網絡接口的各種資訊。
ioctl
首先看ioctl()用法 ioctl()原型如下：
#include <sys/ioctl.h> int ioctl(int fd, int request, ...); 參數： fd ： 檔案描述符 request： 表示要請求的資訊。如IP位址、網絡掩碼等 ... ： 後面的可變參數根據request而定
比如我們請求所有網絡接口的清單：
struct ifconf IoCtlReq;
...
ioctl( Sock, SIOCGIFCONF, &IoCtlReq )
其中 IoCtlReq 是一個
與接口相關的request如下表所示（ 來源： < http://baike.baidu.com/view/1081282.htm?fr=aladdin > ）：
| 接 口 | SIOCGIFCONF SIOCSIFADDR SIOCGIFADDR SIOCSIFFLAGS SIOCGIFFLAGS SIOCSIFDSTADDR SIOCGIFDSTADDR SIOCGIFBRDADDR SIOCSIFBRDADDR SIOCGIFNETMASK SIOCSIFNETMASK SIOCGIFMETRIC SIOCSIFMETRIC SIOCGIFMTU SIOCxxx | 擷取所有接口的清單 設定接口位址 擷取接口位址 設定接口标志 擷取接口标志 設定點到點位址 擷取點到點位址 擷取廣播位址 設定廣播位址 擷取子網路遮罩 設定子網路遮罩 擷取接口的測度 設定接口的測度 擷取接口MTU （還有很多取決于系統的實作） | 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 |
關于ioctl的詳細解釋清查閱本博其它博文
struct ifreq
結構體 struct ifreq用來儲存某個接口的資訊。
// if.h
/*
* 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 {
#define IFHWADDRLEN 6
union
{
char ifrn_name[IFNAMSIZ]; /* if name, e.g. "en0" */
} ifr_ifrn;
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
struct sockaddr ifru_broadaddr;
struct sockaddr ifru_netmask;
struct sockaddr ifru_hwaddr;
short ifru_flags;
int ifru_ivalue;
int ifru_mtu;
struct ifmap ifru_map;
char ifru_slave[IFNAMSIZ]; /* Just fits the size */
char ifru_newname[IFNAMSIZ];
void __user * ifru_data;
struct if_settings ifru_settings;
} ifr_ifru;
};
#define ifr_name ifr_ifrn.ifrn_name /* interface name */
#define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */
#define ifr_addr ifr_ifru.ifru_addr /* address */
#define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-p lnk */
#define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
#define ifr_netmask ifr_ifru.ifru_netmask /* interface net mask */
#define ifr_flags ifr_ifru.ifru_flags /* flags */
#define ifr_metric ifr_ifru.ifru_ivalue /* metric */
#define ifr_mtu ifr_ifru.ifru_mtu /* mtu */
#define ifr_map ifr_ifru.ifru_map /* device map */
#define ifr_slave ifr_ifru.ifru_slave /* slave device */
#define ifr_data ifr_ifru.ifru_data /* for use by interface */
#define ifr_ifindex ifr_ifru.ifru_ivalue /* interface index */
#define ifr_bandwidth ifr_ifru.ifru_ivalue /* link bandwidth */
#define ifr_qlen ifr_ifru.ifru_ivalue /* Queue length */
#define ifr_newname ifr_ifru.ifru_newname /* New name */
#define ifr_settings ifr_ifru.ifru_settings /* Device/proto settings*/
ifr_name 辨別了某一接口。
可以通過ioctl擷取該接口的資訊。如：
ioctl(Sock, SIOCGIFNETMASK, &IfReq);//擷取網絡接口位址掩碼 該代碼需要先對IfReq->ifr_name指派，然後擷取與 IfReq->ifr_name向比對的網絡接口 的位址掩碼
struct ifconf
結構體struct ifconf通常用來儲存所有接口資訊
// if.h
/*
* Structure used in SIOCGIFCONF request.
* Used to retrieve interface configuration
* for machine (useful for programs which
* must know all networks accessible).
*/
struct ifconf {
int ifc_len; /* size of buffer */
union {
char __user *ifcu_buf;
struct ifreq __user *ifcu_req;
} ifc_ifcu;
};
#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req /* array of structures */
該結構體可以用來擷取所喲網絡接口的名字和資訊（不是全部資訊，是ip位址） （圖檔來自： http://tech.sunplusedu.com/space/post-4064.aspx ）
Example：
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <string.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
typedef uint32_t uint32;
#define MAX_IF 10
int
main()
{
struct ifreq ifVec[MAX_IF];//用來儲存所有接口
int sock = -1;
if ( (sock = socket( AF_INET, SOCK_DGRAM, 0 )) < 0 )
fprintf(stderr, "Error:%d, cannot open RAM;\n");
// get if vector
struct ifconf ioIfConf;
ioIfConf.ifc_buf = (void *)ifVec;
ioIfConf.ifc_len = sizeof(ifVec);
printf("Len:%d\n", ioIfConf.ifc_len);
if (ioctl(sock, SIOCGIFCONF, &ioIfConf) < 0 )//擷取所有網絡接口資訊
fprintf(stderr, "Error:%d ioctl IFCONF\n");
printf("Len:%d\n", ioIfConf.ifc_len);// 和前面到len對比，發現ioctl修改裡len到大小
//循環列印每個網絡接口到資訊
{
struct ifreq *ifPt;
struct ifreq *ifEndPt;
ifPt = ifVec;
ifEndPt = (void *)((char *)ifVec + ioIfConf.ifc_len);
for (ifPt = ifVec; ifPt < ifEndPt; ifPt++)
{
struct ifreq ifReq;
if ( ifPt->ifr_addr.sa_family != AF_INET ) {
continue;
}
// Temp keepers of interface params...
uint32 u32_addr, u32_mask;
/* 列印ip位址 */
char ipDotBuf[16], subnetDotBuf[16], maskDotBuf[16]; // 儲存點分十進制到ip位址
u32_addr = ((struct sockaddr_in *)&ifPt->ifr_addr)->sin_addr.s_addr;
inet_ntop(AF_INET, &u32_addr, ipDotBuf, (socklen_t )sizeof(ipDotBuf));
printf("IP Address: %s\n", ipDotBuf);
/* 列印位址掩碼 */
bzero(&ifReq,sizeof(struct ifreq));
memcpy(ifReq.ifr_name, ifPt->ifr_name, sizeof(ifReq.ifr_name));
if (ioctl(sock, SIOCGIFNETMASK, &ifReq ) < 0){
fprintf(stderr, "Error: %d, cannot get mask\n", errno);
}
else{
u32_mask = ((struct sockaddr_in *)&ifReq.ifr_addr)->sin_addr.s_addr;
inet_ntop(AF_INET, &u32_mask, maskDotBuf, (socklen_t )sizeof(maskDotBuf));
printf("Mask: %s\n", maskDotBuf);
}
/* 列印MTU */
bzero(&ifReq,sizeof(struct ifreq));
memcpy(ifReq.ifr_name, ifPt->ifr_name, sizeof(ifReq.ifr_name));
if (ioctl(sock, SIOCGIFMTU, &ifReq ) < 0){
fprintf(stderr, "Error: %d, cannot get MTU\n", errno);
}
else{
printf("SIOCGIFMTU:%d\n", ifReq.ifr_mtu);
}
/* 其他資訊的列印方式與掩碼和MTU相同 */
}
}
}
運作結果：
[email protected]:~/Windeal/apue$ ./exe
Len:320
Len:64
IP Address: 127.0.0.1
Mask: 255.0.0.0
SIOCGIFMTU:16436
IP Address: 172.17.92.198
Mask: 255.255.254.0
SIOCGIFMTU:1500
[email protected]:~/Windeal/apue$