C 打印出网络掩码

我一直在编写一个程序，其中列出了我的计算机的所有IP地址、网络掩码和接口名称，但我在打印网络掩码时遇到了一个问题。这个问题似乎只发生在IPv6上。代码如下：

int i;
struct ifaddrs *ifap, *ifa;


    getifaddrs(&ifap);
    char *net_mask = NULL; 
    int buffer_size = 200;
    char *ifa_addr = NULL;

    for (ifa = ifap; ifa; ifa = ifa->ifa_next)
    {
        struct sockaddr_in *ifan = (struct sockaddr_in *) ifa->ifa_netmask; //interface netmask
        struct sockaddr_in *ifaa_in = (struct sockaddr_in*)ifa->ifa_addr; //interface address

        //same as above with the exception that it is for ipv6
        struct sockaddr_in6 *ifan6 = (struct sockaddr_in6 *) ifa->ifa_netmask;
        struct sockaddr_in6 *ifaa_in6 = (struct sockaddr_in6*)ifa->ifa_addr;
        char *prevNet_mask = net_mask;
        net_mask = (char*)calloc(buffer_size, sizeof(char*));
        ifa_addr = (char*)calloc(buffer_size, sizeof(char*));

        inet_ntop(ifa->ifa_addr->sa_family,ifa->ifa_addr->sa_family == AF_INET?(void*)&ifan->sin_addr : (void*)&ifan6->sin6_addr, net_mask, buffer_size);
        inet_ntop(ifa->ifa_addr->sa_family, ifa->ifa_addr->sa_family == AF_INET?(void*)&ifaa_in->sin_addr: (void*)&ifaa_in6->sin6_addr ,ifa_addr , buffer_size);
        printf("Interface: %s\tNetMask: %s", ifa->ifa_name, net_mask);

        //space evenly
        int num_spaces = strlen(net_mask) - 40;
        if(num_spaces < 0) num_spaces *= -1;
        for(i = 0; i <num_spaces;i++) printf(" ");

        printf("Address: %s\n",ifa_addr);
    }

---

似乎有些接口的ipv6网络掩码不完整。有人能解释一下为什么会这样吗？

网络掩码不是不完整的，双冒号表示一个或多个连续的零块。

我看不出有什么不对。基本上有两个IPv6掩码（IPv6实际上只使用CIDR表示法）：

/64

和

/128

。您的

/64

掩码在

ffff:ffff:ffff:ffff:：

处正确，而

/128

掩码在

ffff:ffff:ffff:ffff处正确。IPv6将使用这些，并且，可能，
/127
用于点到点链接。@RonMaupin我知道这有点晚了，但我觉得这个问题不值得发表自己的文章。话虽如此，有没有一种方法可以使接口名不是一堆随机字母？例如，我的计算机上的一个接口的名称是isatap.attlocal.net您指的是一个DNS名称。@RonMaupin真的是因为当我使用终端查找我的计算机上的所有接口时，显示的是“隧道适配器isatap.attlocal.net”。我之所以这样说是因为我正在尝试确定哪个接口是我的无线LAN适配器。你的操作系统正在将它附加到它决定调用它的接口的DNS域。接口的名称完全是操作系统的，有时还依赖于用户。用户可以在某些操作系统（如Windows）中更改界面名称（isatap）的内容。
Interface: {BE3A9EA6-72AB-40FD-9036-9AC6BA4D75CF}       NetMask: ffff:ffff:ffff:ffff::                   Address: fe80::9cfb:3ebd:d866:e214
Interface: {BE3A9EA6-72AB-40FD-9036-9AC6BA4D75CF}       NetMask: 255.255.0.0                             Address: 169.254.226.20
Interface: {AA4D555F-C490-40DE-9F61-8E5AB3252389}       NetMask: ffff:ffff:ffff:ffff::                   Address: fe80::e994:389a:9ab4:1e45
Interface: {AA4D555F-C490-40DE-9F61-8E5AB3252389}       NetMask: 255.255.0.0                             Address: 169.254.30.69
Interface: {E1AE93D7-66CC-4651-A470-1445CC777F36}       NetMask: ffff:ffff:ffff:ffff::                   Address: fe80::5837:88eb:5801:273e
Interface: {E1AE93D7-66CC-4651-A470-1445CC777F36}       NetMask: 255.255.0.0                             Address: 169.254.39.62
Interface: {A251C284-7DC3-4F56-AB6A-8A4E4E218B6F}       NetMask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff Address: 2602:306:8390:10f0::43
Interface: {A251C284-7DC3-4F56-AB6A-8A4E4E218B6F}       NetMask: ffff:ffff:ffff:ffff::                   Address: 2602:306:8390:10f0:6810:b0eb:1287:3138
Interface: {A251C284-7DC3-4F56-AB6A-8A4E4E218B6F}       NetMask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff Address: 2602:306:8390:10f0:116d:50d0:4291:c8ab
Interface: {A251C284-7DC3-4F56-AB6A-8A4E4E218B6F}       NetMask: ffff:ffff:ffff:ffff::                   Address: fe80::6810:b0eb:1287:3138
Interface: {A251C284-7DC3-4F56-AB6A-8A4E4E218B6F}       NetMask: 255.255.255.0                           Address: 192.168.1.70
Interface: {D301A0B1-F567-11E5-A797-806E6F6E6963}       NetMask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff Address: ::1
Interface: {D301A0B1-F567-11E5-A797-806E6F6E6963}       NetMask: 255.0.0.0                               Address: 127.0.0.1
Interface: {01CEB8B7-97FE-40AC-A5D4-47A61834A467}       NetMask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff Address: fe80::5efe:c0a8:146
Interface: {4ED4A6C1-0496-4F0B-AD77-395C9F275D41}       NetMask: ffff:ffff:ffff:ffff::                   Address: 2001:0:9d38:90d7:2c9a:771:97c6:fef0
Interface: {4ED4A6C1-0496-4F0B-AD77-395C9F275D41}       NetMask: ffff:ffff:ffff:ffff::                   Address: fe80::2c9a:771:97c6:fef0
Interface: {A8CF5839-BA78-4C69-865E-3BE15F9F9A2C}       NetMask: 0.0.0.0                                 Address: 0.0.0.0