if_nametoindex, if_indextoname——网络接口名与索引值之间的映射

说明

NAME
       if_nametoindex, if_indextoname - mappings between network interface names and indexes

SYNOPSIS
       #include <net/if.h>

       unsigned int if_nametoindex(const char *ifname);

       char *if_indextoname(unsigned int ifindex, char *ifname);

DESCRIPTION
       The  if_nametoindex() function returns the index of the network interface corresponding to the name
       ifname.

       The if_indextoname() function returns the name of the network interface corresponding to the inter‐
       face  index ifindex.  The name is placed in the buffer pointed to by ifname.  The buffer must allow
       for the storage of at least IF_NAMESIZE bytes.

RETURN VALUE
       On success, if_nametoindex() returns the index number of the network  interface;  on  error,  0  is
       returned and errno is set appropriately.

       On  success, if_indextoname() returns ifname; on error, NULL is returned and errno is set appropri‐
       ately.
ERRORS
       if_nametoindex() may fail and set errno if:

       ENODEV No interface found with given name.

       if_indextoname() may fail and set errno if:

       ENXIO  No interface found for the index.

       if_nametoindex() and if_indextoname() may also fail for any of the errors specified  for  socket(2)
       or ioctl(2).

• if_nametoindex()：指定网络接口名称字符串作为参数；若该接口存在，则返回相应的索引，否则返回0
• if_indextoname()：指定网络接口索引以及一块长度至少为IF_NAMESIZE(16)字节的内存区域作为参数；若索引对应的网络接口存在，则在内存区域中返回该接口的名称字符串，否则返回NULL，并将errno设置为相应的值