使用函数getifaddrs来枚举网卡IP,当中使用到的结构体例如以下所看到的:
struct ifaddrs
{
struct ifaddrs *ifa_next; /* Next item in list */
char *ifa_name; /* Name of interface */
unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */
struct sockaddr *ifa_addr; /* Address of interface */
struct sockaddr *ifa_netmask; /* Netmask of interface */
union
{
struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */
struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */
} ifa_ifu;
#define ifa_broadaddr ifa_ifu.ifu_broadaddr
#define ifa_dstaddr ifa_ifu.ifu_dstaddr
void *ifa_data; /* Address-specific data */
};
ifa_next指向链表的下一个成员。
ifa_name是接口名称,以0结尾的字符串。比方eth0,lo;
ifa_flags是接口的标识位(比方当IFF_BROADCAST或IFF_POINTOPOINT设置到此标识位时,影响联合体变量ifu_broadaddr存储广播地址或ifu_dstaddr记录点对点地址);
ifa_netmask存储该接口的子网掩码。结构体变量存储广播地址或点对点地址(见括弧介绍ifa_flags);
ifa_data存储了该接口协议族的特殊信息,它一般是NULL(一般不关注他)。
函数getifaddrs(int getifaddrs (struct ifaddrs **__ifap))获取本地网络接口信息,将之存储于链表中,链表头结点指针存储于__ifap中带回,函数执行成功返回0,失败返回-1,且为errno赋值。
编程实现本机IP地址获取:
#include <stdio.h>
#include <sys/types.h>
#include <ifaddrs.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
int main (int argc, const char * argv[]) {
struct ifaddrs * ifAddrStruct=NULL;
struct ifaddrs * ifa=NULL;
void * tmpAddrPtr=NULL;
getifaddrs(&ifAddrStruct);
for (ifa = ifAddrStruct; ifa != NULL; ifa = ifa->ifa_next) {
if (ifa ->ifa_addr->sa_family==AF_INET) { // check it is IP4
// is a valid IP4 Address
tmpAddrPtr=&((struct sockaddr_in *)ifa->ifa_addr)->sin_addr;
char addressBuffer[INET_ADDRSTRLEN];
inet_ntop(AF_INET, tmpAddrPtr, addressBuffer, INET_ADDRSTRLEN);
printf("%s IP Address %s\n", ifa->ifa_name, addressBuffer);
} else if (ifa->ifa_addr->sa_family==AF_INET6) { // check it is IP6
// is a valid IP6 Address
tmpAddrPtr=&((struct sockaddr_in6 *)ifa->ifa_addr)->sin6_addr;
char addressBuffer[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, tmpAddrPtr, addressBuffer, INET6_ADDRSTRLEN);
printf("%s IP Address %s\n", ifa->ifa_name, addressBuffer);
}
}
if (ifAddrStruct!=NULL) freeifaddrs(ifAddrStruct);
return 0;
}
在server上执行,获得的结果例如以下图: