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获取网络接口信息——ioctl()函数与结构体struct ifreq、 struct ifconf
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Linux 下 可以使用ioctl()函数 以及 结构体 struct ifreq 结构体struct ifconf来获取网络接口的各种信息。
ioctl
首先看ioctl()用法
ioctl()原型如下:
#include <sys/ioctl.h>
int ioctl(int fd, int request, ...);
参数:
fd : 文件描述符
request: 表示要请求的信息。如IP地址、网络掩码等
... : 后面的可变参数根据request而定
比如我们请求所有网络接口的清单:
struct ifconf IoCtlReq; ... ioctl( Sock, SIOCGIFCONF, &IoCtlReq )
其中IoCtlReq 是一个
与接口相关的request如下表所示(来源: <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 | 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 |
关于ioctl的详细解释清查阅本博其它博文
struct ifreq
结构体 struct ifreq用来保存某个接口的信息。
// 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 标识了某一接口。
可以通过ioctl获取该接口的信息。如:
ioctl(Sock, SIOCGIFNETMASK, &IfReq);//获取网络接口地址掩码
该代码需要先对IfReq->ifr_name赋值,然后获取与IfReq->ifr_name向匹配的网络接口 的地址掩码
struct ifconf
结构体struct ifconf通常用来保存所有接口信息
// 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 */
该结构体可以用来获取所哟网络接口的名字和信息(不是全部信息,是ip地址)
(图片来自: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];//用来保存所有接口 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 )//获取所有网络接口信息 fprintf(stderr, "Error:%d ioctl IFCONF\n"); printf("Len:%d\n", ioIfConf.ifc_len);// 和前面到len对比,发现ioctl修改里len到大小 //循环打印每个网络接口到信息 { 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; /* 打印ip地址 */ char ipDotBuf[16], subnetDotBuf[16], maskDotBuf[16]; // 保存点分十进制到ip地址 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); /* 打印地址掩码 */ 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); } /* 打印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); } /* 其他信息的打印方式与掩码和MTU相同 */ } } }
运行结果:
windeal@ubuntu:~/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 windeal@ubuntu:~/Windeal/apue$
获取网络接口信息——ioctl()函数与结构体struct ifreq、 struct ifconf
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