/*=============================================================注意:结构体之间不能直接进行强制转换, 必须先转换成指针类型才可以进行结构体间的类型转换, 这里需要明确的定义就是什么才叫强制转换.强制转换是将内存中一段代码以另一种不同类型的方式进行解读, 因此转换的空间必须与源空间一一对应.而结构体则是由不固定的多种类型变量组合而成, 因此强制转换时并不确定原格式与目标格式确定的对应关系, 例如一个结构体为3个变量, 而另一个则为2个, 那么就无法确定如何分配.因此最简单的让计算机可以理解的方式就是先将结构体转换成指针, 然后将指针转换成目标格式, 再读取转换后的指针, 这样计算机就会按照指针的格式读取特定目标代码段了.
//接口配置结构体#include<net/if.h>struct ifconf { int ifc_len;// 缓冲区的大小 union { caddr_t ifcu_buf; // input from user->kernel struct ifreq *ifcu_req; // return of structures returned 注意:是指针类型, 要指向目标数据 }ifc_ifcu;};#define ifc_buf ifc_ifcu.ifcu_buf //buffer address#define ifc_req ifc_ifcu.ifcu_req //array of structures returned
//接口地址结构体#include<net/if.h>struct ifreq{ char ifr_name[IFNAMSIZ];// interface name, e.g., “le0” union { struct sockaddr ifru_addr; struct sockaddr ifru_dstaddr; struct sockaddr ifru_broadaddr; short ifru_flags; int ifru_metric; caddr_t ifru_data; }ifr_ifru;};#define ifr_addr ifr_ifru.ifru_addr // address#define ifr_dstaddr ifr_ifru.ifru_dstaddr // otner 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
//通用网络地址结构体#include<sys/socket.h>struct sockaddr { unsigned short sa_family; //address family, AF_xxx char sa_data[14]; //14 bytes of protocol address };
//IPV4网络地址结构体#include<netinet/in.h>struct sockaddr_in { short int sin_family; //Address family unsigned short int sin_port; //Port number struct in_addr sin_addr; //Internet address unsigned char sin_zero[8]; //Same size as struct sockaddr};
//网络二进制地址结构体#include<arpa/inet.h>struct in_addr { unsigned long s_addr;};
in_addr_t//网络二进制数格式, 与 struct in_addr 中的 s_addr 一致
#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>
//将点分十进制地址 cp 转换为网络二进制数存入 inpint inet_aton(const char *cp, struct in_addr *inp);
inet_aton() converts the Internet host address cp from the standard/ numbers-and-dots notation into binary data and stores it in the struc-/ ture that inp points to. inet_aton() returns non-zero if the address is/ valid, zero if not.
//将网络二进制数转换为点分十进制char *inet_ntoa(struct in_addr in);
inet_ntoa() function converts the Internet host address in given in/ network byte order to a string in standard numbers-and-dots notation./ The string is returned in a statically allocated buffer, which subse-/ quent calls will overwrite.
//将点分十进制地址 cp 转换为网络二进制数返回in_addr_t inet_addr(const char *cp);
inet_addr() function converts the Internet host address cp from/ numbers-and-dots notation into binary data in network byte order. If/ the input is invalid, INADDR_NONE (usually -1) is returned. This is an/ obsolete interface to inet_aton(), described immediately above; it is/ obsolete because -1 is a valid address (255.255.255.255), and/ inet_aton() provides a cleaner way to indicate error return.
//将点分十进制地址 cp 转换为网络二进制数返回in_addr_t inet_network(const char *cp);
inet_network() function extracts a number suitable for use as an/ Internet address in host byte order from the address cp in numbers-and-/ dots notation. If the input is invalid, -1 is returned.
//从地址返回主机地址部分的主机序列二进制数in_addr_t inet_lnaof(struct in_addr in);
inet_lnaof() function returns the local host address part of the/ Internet address in. The local host address is returned in local host/ byte order.
//从地址返回网络地址部分的主机序列二进制数in_addr_t inet_netof(struct in_addr in);
inet_netof() function returns the network number part of the Inter-/ net Address in. The network number is returned in local host byte/ order.
//根据网络地址和主机地址生成子掩码struct in_addr inet_makeaddr(int net, int host);
inet_makeaddr() function makes an Internet host address in network/ byte order by combining the network number net with the local address/ host in network net, both in local host byte order.=============================================================*/
int main(int argc, char *argv[]){ int inet_sock; struct ifreq ifr; //建立套接字 inet_sock = socket(AF_INET, SOCK_DGRAM, 0); //获得接口地址 bzero(&ifr, sizeof(ifr)); strcpy(ifr.ifr_name, "eth0"); if (ioctl(inet_sock, SIOCGIFADDR, &ifr) < 0) perror("ioctl"); printf("host:%s/n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_addr))->sin_addr)); //获得广播地址 bzero(&ifr, sizeof(ifr)); strcpy(ifr.ifr_name, "eth0"); if (ioctl(inet_sock, SIOCGIFBRDADDR, &ifr) < 0) perror("ioctl"); printf("broadcast:%s/n", inet_ntoa(((struct sockaddr_in*)&(ifr.ifr_addr))->sin_addr)); return 0;}
