linux下c获取网卡信息

谁借莪１个温暖的怀抱￠ 2021-09-21 07:08 492阅读 0赞

在Linux下开发网络程序时，经常会遇到需要取本地网络接口名、IP、广播地址、子网掩码或者MAC地址等信息的需求，最常见的办法是配合宏SIOCGIFHWADDR、SIOCGIFADDR、SIOCGIFBRDADDR与SIOCGIFNETMASK作为参数调用函数ioctl分别获得MAC地址、IP地址、广播地址与子网掩码来实现。一次性获取此类信息的C语言代码实现如下。

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

1 #include <stdio.h>
      2 #include <string.h>
      3 #include <net/if.h>
      4 #include <sys/ioctl.h>
      5 #include <arpa/inet.h>
      6 #include <errno.h>
      7 
      8 int getLocalInfo(void)
      9 {
     10     int fd;
     11     int interfaceNum = 0;
     12     struct ifreq buf[16];
     13     struct ifconf ifc;
     14     struct ifreq ifrcopy;
     15     char mac[16] = {0};
     16     char ip[32] = {0};
     17     char broadAddr[32] = {0};
     18     char subnetMask[32] = {0};
     19 
     20     if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
     21     {
     22         perror("socket");
     23 
     24         close(fd);
     25         return -1;
     26     }
     27 
     28     ifc.ifc_len = sizeof(buf);
     29     ifc.ifc_buf = (caddr_t)buf;
     30     if (!ioctl(fd, SIOCGIFCONF, (char *)&ifc))
     31     {
     32         interfaceNum = ifc.ifc_len / sizeof(struct ifreq);
     33         printf("interface num = %dn", interfaceNum);
     34         while (interfaceNum-- > 0)
     35         {
     36             printf("ndevice name: %sn", buf[interfaceNum].ifr_name);
     37 
     38             //ignore the interface that not up or not runing  
     39             ifrcopy = buf[interfaceNum];
     40             if (ioctl(fd, SIOCGIFFLAGS, &ifrcopy))
     41             {
     42                 printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
     43 
     44                 close(fd);
     45                 return -1;
     46             }
     47 
     48             //get the mac of this interface  
     49             if (!ioctl(fd, SIOCGIFHWADDR, (char *)(&buf[interfaceNum])))
     50             {
     51                 memset(mac, 0, sizeof(mac));
     52                 snprintf(mac, sizeof(mac), "%02x%02x%02x%02x%02x%02x",
     53                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[0],
     54                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[1],
     55                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[2],
     56 
     57                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[3],
     58                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[4],
     59                     (unsigned char)buf[interfaceNum].ifr_hwaddr.sa_data[5]);
     60                 printf("device mac: %sn", mac);
     61             }
     62             else
     63             {
     64                 printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
     65                 close(fd);
     66                 return -1;
     67             }
     68 
     69             //get the IP of this interface  
     70 
     71             if (!ioctl(fd, SIOCGIFADDR, (char *)&buf[interfaceNum]))
     72             {
     73                 snprintf(ip, sizeof(ip), "%s",
     74                     (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_addr))->sin_addr));
     75                 printf("device ip: %sn", ip);
     76             }
     77             else
     78             {
     79                 printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
     80                 close(fd);
     81                 return -1;
     82             }
     83 
     84             //get the broad address of this interface  
     85 
     86             if (!ioctl(fd, SIOCGIFBRDADDR, &buf[interfaceNum]))
     87             {
     88                 snprintf(broadAddr, sizeof(broadAddr), "%s",
     89                     (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_broadaddr))->sin_addr));
     90                 printf("device broadAddr: %sn", broadAddr);
     91             }
     92             else
     93             {
     94                 printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
     95                 close(fd);
     96                 return -1;
     97             }
     98  99 
    100             //get the subnet mask of this interface  
    101             if (!ioctl(fd, SIOCGIFNETMASK, &buf[interfaceNum]))
    102             {
    103                 snprintf(subnetMask, sizeof(subnetMask), "%s",
    104                     (char *)inet_ntoa(((struct sockaddr_in *)&(buf[interfaceNum].ifr_netmask))->sin_addr));
    105                 printf("device subnetMask: %sn", subnetMask);
    106             }
    107             else
    108             {
    109                 printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
    110                 close(fd);
    111                 return -1;
    112 
    113             }
    114         }
    115     }
    116     else
    117     {
    118         printf("ioctl: %s [%s:%d]n", strerror(errno), __FILE__, __LINE__);
    119         close(fd);
    120         return -1;
    121     }
    122   
    123     close(fd);
    124 
    125     return 0;
    126 }
    127   
    128 int main(void)
    129 {
    130     getLocalInfo();
    131 
    132     return 0;
    133 }

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

使用ioctl函数虽然可以获取所有的信息，但是使用起来比较麻烦，如果不需要获取MAC地址，那么使用getifaddrs函数来获取更加方便与简洁。值得一提的是，在MacOS或iOS系统上（如iPhone程序开发），上述iotcl函数没法获得mac地址跟子网掩码，这个使用，使用getifaddrs函数便更有优势了。下面是使用getiaddrs函数获取网卡信息的C语言代码实现。

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

1 #include <stdio.h>  
     2 #include <ifaddrs.h>  
     3 #include <arpa/inet.h>  
     4   
     5 int getSubnetMask()
     6 {
     7     struct sockaddr_in *sin = NULL;
     8     struct ifaddrs *ifa = NULL, *ifList;
     9 
    10     if (getifaddrs(&ifList) < 0)
    11     {
    12         return -1;
    13     }
    14 
    15     for (ifa = ifList; ifa != NULL; ifa = ifa->ifa_next)
    16     {
    17         if(ifa->ifa_addr->sa_family == AF_INET)
    18         {
    19             printf("n>>> interfaceName: %sn", ifa->ifa_name);
    20 
    21             sin = (struct sockaddr_in *)ifa->ifa_addr;
    22             printf(">>> ipAddress: %sn", inet_ntoa(sin->sin_addr));
    23 
    24             sin = (struct sockaddr_in *)ifa->ifa_dstaddr;
    25             printf(">>> broadcast: %sn", inet_ntoa(sin->sin_addr));
    26 
    27             sin = (struct sockaddr_in *)ifa->ifa_netmask;
    28             printf(">>> subnetMask: %sn", inet_ntoa(sin->sin_addr));
    29         }
    30     }
    31 
    32     freeifaddrs(ifList);
    33 
    34     return 0;
    35 }
    36   
    37 int main(void)
    38 {
    39     getSubnetMask();
    40 
    41     return 0;
    42 }

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

ifaddrs结构体定义如下：

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

1 struct ifaddrs   
     2 {   
     3     struct ifaddrs  *ifa_next;    /* Next item in list */   
     4     char            *ifa_name;    /* Name of interface */   
     5     unsigned int     ifa_flags;   /* Flags from SIOCGIFFLAGS */   
     6     struct sockaddr *ifa_addr;    /* Address of interface */   
     7     struct sockaddr *ifa_netmask; /* Netmask of interface */   
     8     union   
     9     {   
    10         struct sockaddr *ifu_broadaddr; /* Broadcast address of interface */   
    11         struct sockaddr *ifu_dstaddr; /* Point-to-point destination address */   
    12     } ifa_ifu;   
    13     #define              ifa_broadaddr ifa_ifu.ifu_broadaddr   
    14     #define              ifa_dstaddr   ifa_ifu.ifu_dstaddr   
    15     void            *ifa_data;    /* Address-specific data */   
    16 };

![复制代码][aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]

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，比如eth0，lo；ifa\_flags是接口的标识位（比如当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，它通常是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。  
    很显然，函数getifaddrs用于获取本机接口信息，比如最典型的获取本机IP地址。

[aHR0cHM6Ly9jb21tb24uY25ibG9ncy5jb20vaW1hZ2VzL2NvcHljb2RlLmdpZg]: /images/20210920/61c779ec90b046ee891b9d87e04f7f93.png