如何获取当前配置的IPV6地址的前缀长度（掩码）

来源：互联网发布：招商证券交易软件编辑：程序博客网时间：2024/06/05 00:12

首先问个问题：IPV6是否有掩码？

答：有

GOOGLE上查了一圈没有找到好的方法，字节摸索了一套可行的方法，同分享：

下述程序打印处掩码长度，由此判断前缀长度，good！

       #include <sys/socket.h>       #include <netdb.h>       #include <ifaddrs.h>       #include <stdio.h>       #include <stdlib.h>       #include <unistd.h>       #include <net/if.h>       #include <netinet/in.h>        #include <sys/types.h>       int       main(int argc, char *argv[])       {           struct ifaddrs *ifaddr, *ifa;           int family, s;           char host[NI_MAXHOST];   char host_netmask[NI_MAXHOST];   struct sockaddr_in6  *pip6 = NULL;           int i;           if (getifaddrs(&ifaddr) == -1) {               perror("getifaddrs");               exit(EXIT_FAILURE);           }           /* Walk through linked list, maintaining head pointer so we              can free list later */           for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {               if (ifa->ifa_addr == NULL)                   continue;               family = ifa->ifa_addr->sa_family;               /* Display interface name and family (including symbolic                  form of the latter for the common families) */               printf("%s  address family: %d%s\n",                       ifa->ifa_name, family,                       (family == AF_PACKET) ? " (AF_PACKET)" :                       (family == AF_INET) ?   " (AF_INET)" :                       (family == AF_INET6) ?  " (AF_INET6)" : "");               /* For an AF_INET* interface address, display the address */               if (family == AF_INET || family == AF_INET6) {                   s = getnameinfo(ifa->ifa_addr,                           (family == AF_INET) ? sizeof(struct sockaddr_in) :                                                 sizeof(struct sockaddr_in6),                           host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);                   if (s != 0) {                       printf("getnameinfo() failed: %s\n", gai_strerror(s));                       exit(EXIT_FAILURE);                   }   getnameinfo(ifa->ifa_netmask,                               (family == AF_INET)? sizeof(struct sockaddr_in): sizeof(struct sockaddr_in6),                                host_netmask, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);   if(AF_INET6==family)   {pip6 = (struct sockaddr_in6 *)(ifa->ifa_netmask);char *p = (char *)&(pip6->sin6_addr);                        for(i=0;i<16;i++)                        {printf("%d ",*p);p++;}   }                   printf("\taddress: <%s>\n", host);                   printf("\tnetmaks: <%s>\n", host_netmask);               }           }           freeifaddrs(ifaddr);           exit(EXIT_SUCCESS);       }