Inet – Comtrol eCos User Manual

Page 533

Chapter 38. TCP/IP Library Reference

struct if_nameindex *

if_nameindex(void);

void

if_freenameindex(struct if_nameindex *ptr);

DESCRIPTION

These functions map interface indexes to interface names (such as

“lo0”), and vice versa.

The if_nametoindex() function converts an interface name specified by the

ifname argument to an interface index (positive integer value).

If the

specified interface does not exist, 0 will be returned.

if_indextoname() converts an interface index specified by the ifindex

argument to an interface name.

The ifname argument must point to a

buffer of at least IF_NAMESIZE bytes into which the interface name corre-

sponding to the specified index is returned.

(IF_NAMESIZE is also

defined in

net/if.h> and its value includes a terminating null byte at

the end of the interface name.)

This pointer is also the return value of

the function.

If there is no interface corresponding to the specified

index, NULL is returned.

if_nameindex() returns an array of if_nameindex structures.

if_nametoindex is also defined in

net/if.h>, and is as follows:

struct if_nameindex {

unsigned int

if_index;

/* 1, 2, ... */

char

*if_name;

/* null terminated name: "le0", ... */

};

The end of the array of structures is indicated by a structure with an

if_index of 0 and an if_name of NULL.

The function returns a null

pointer on error.

The memory used for this array of structures along

with the interface names pointed to by the if_name members is obtained

dynamically.

This memory is freed by the if_freenameindex() function.

if_freenameindex() takes a pointer that was returned by if_nameindex() as

argument (ptr), and it reclaims the region allocated.

DIAGNOSTICS

if_nametoindex() returns 0 on error, positive integer on success.

if_indextoname() and if_nameindex() return NULL on errors.