一、struct ifconf结构体
- 功能：用来保存所有网络接口的名字和信息（不是全部信息，是ip地址）
// 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 */
- 功能：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*/
| 类别 | Request | 说明 | 数据类型 |
|
接 口 |
SIOCGIFCONF | 获取所有接口的清单 | struct ifconf |
| SIOCSIFADDR | 设置接口地址 | struct ifreq | |
| SIOCGIFADDR | 获取接口地址 | struct ifreq | |
| SIOCSIFFLAGS | 设置接口标志 | struct ifreq | |
| SIOCGIFFLAGS | 获取接口标志 | struct ifreq | |
| SIOCSIFDSTADDR | 设置点到点地址 | struct ifreq | |
| SIOCGIFDSTADDR | 获取点到点地址 | struct ifreq | |
| SIOCGIFBRDADDR | 获取广播地址 | struct ifreq | |
| SIOCSIFBRDADDR | 设置广播地址 | struct ifreq | |
| SIOCGIFNETMASK | 获取子网掩码 | struct ifreq | |
| SIOCSIFNETMASK | 设置子网掩码 | struct ifreq | |
| SIOCGIFMETRIC | 获取接口的测度 | struct ifreq | |
| SIOCSIFMETRIC | 设置接口的测度 | struct ifreq | |
| SIOCGIFMTU | 获取接口MTU | struct ifreq | |
| SIOCxxx | （还有很多取决于系统的实现） |
比如我们请求所有网络接口的清单：
struct ifconf IoCtlReq; ... ioctl(Sock, SIOCGIFCONF, &IoCtlReq );
演示案例：
- 获取"eth0"网卡接口的地址掩码
#include <stdio.h> #include <stdlib.h> #include <sys/ioctl.h> #include <netinet/in.h> #include <arpa/inet.h> #include <sys/socket.h> #include <sys/types.h> #include <net/if.h> #include <unistd.h> #include <string.h> int main() { //此处我们的实验对象为eth0这块网卡 struct ifreq ifr; strcpy (ifr.ifr_name, "eth0"); //打开一个通信socket int sock = -1; if ((sock=socket( AF_INET, SOCK_DGRAM, 0 )) < 0 ) return -1; uint32_t u32_mask; char maskDotBuf[16]; //获取eth0这个借口的掩码 ioctl(sock, SIOCGIFNETMASK, &ifr); //获取掩码地址（这是网络字节序的地址格式） u32_mask = ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr.s_addr; //将网络字节序的掩码地址转换为本地点分二进制字符串格式的 inet_ntop(AF_INET, &u32_mask, maskDotBuf, (socklen_t )sizeof(maskDotBuf)); //打印掩码 printf("Mask: %s\n", maskDotBuf); return 0; }
演示案例：
- 打印主机中所有的网络接口地址及信息
#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 */ } } }
演示案例
- 下面演示在TCP/UDP通信中，通过struct ifreq结构体获取一个指定的接口地址作为本次通信的IP地址
int listen_fd; if (-1 == (listen_fd = socket (AF_INET, SOCK_STREAM, 0))){ return -1; } //获取eth0接口的信息 struct ifreq ifr; strcpy (ifr.ifr_name, "eth0"); if (ioctl (listen_fd, SIOCGIFADDR, &ifr) < 0){ return -1; } struct sockaddr_in myaddr; myaddr.sin_family = AF_INET; myaddr.sin_port = htons (8888); //将eth0接口的IP地址作为本次通信的IP地址 myaddr.sin_addr.s_addr =((struct sockaddr_in *) &(ifr.ifr_addr))->sin_addr.s_addr;
