tst_if_index_to_name - Maps an interface index into its corresponding name
To check if ifindex is an interface index then the function shall return the value supplied in ifname, which points to a buffer now containing the interface name.
./tst_if_index_to_name [-tooloption ...] -tooloption : v6api tool option
1. The argument ifindex is the interface index of lo, shall return ifname "lo" 2. The argument ifindex is the interface index of Link0, shall return "Link0 name"
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RFC 3493
4.2 Index-to-Name
The second function maps an interface index into its corresponding name.
#include <net/if.h>
char *if_indextoname(unsigned int ifindex, char *ifname);
When this function is called, the ifname argument shall point to a buffer of at least IF_NAMESIZE bytes. The function shall place in this buffer the name of the interface with index ifindex. (IF_NAMESIZE is also defined in <net/if.h> and its value includes a terminating null byte at the end of the interface name.) If ifindex is an interface index, then the function shall return the value supplied in ifname, which points to a buffer now containing the interface name. Otherwise, the function shall return a NULL pointer and set errno to indicate the error. If there is no interface corresponding to the specified index, errno is set to ENXIO. If there was a system error (such as running out of memory), errno would be set to the proper value (e.g., ENOMEM).