系统信息

操作系统：

# lsb_release -ir

Distributor ID: CentOS

Release: 6.7

内核版本：

# uname -r

2.6.32-573.26.1.el6.x86_64

gcc版本：

# gcc --version

gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-16)

Copyright (C) 2010 Free Software Foundation, Inc.

This is free software; see the source for copying conditions. There is NO

warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

glibc版本：

# ldd $(which ls)

linux-vdso.so.1 => (0x00007ffc14d08000)

libselinux.so.1 => /lib64/libselinux.so.1 (0x0000003b2ec00000)

librt.so.1 => /lib64/librt.so.1 (0x0000003b2e400000)

libcap.so.2 => /lib64/libcap.so.2 (0x0000003b2fc00000)

libacl.so.1 => /lib64/libacl.so.1 (0x0000003b36000000)

libc.so.6 => /lib64/libc.so.6 (0x0000003b2d400000)

libdl.so.2 => /lib64/libdl.so.2 (0x0000003b2dc00000)

/lib64/ld-linux-x86-64.so.2 (0x0000003b2d000000)

libpthread.so.0 => /lib64/libpthread.so.0 (0x0000003b2d800000)

libattr.so.1 => /lib64/libattr.so.1 (0x0000003b2f800000)

# /lib64/libc.so.6

GNU C Library stable release version 2.12, by Roland McGrath et al.

Copyright (C) 2010 Free Software Foundation, Inc.

This is free software; see the source for copying conditions.

There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A

PARTICULAR PURPOSE.

Compiled by GNU CC version 4.4.7 20120313 (Red Hat 4.4.7-16).

Compiled on a Linux 2.6.32 system on 2016-02-16.

Available extensions:

The C stubs add-on version 2.1.2.

crypt add-on version 2.1 by Michael Glad and others

GNU Libidn by Simon Josefsson

Native POSIX Threads Library by Ulrich Drepper et al

BIND-8.2.3-T5B

RT using linux kernel aio

libc ABIs: UNIQUE IFUNC

For bug reporting instructions, please see:

.

函数定义

#include

unsigned if_nametoindex(const char *ifname);

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

struct if_nameindex *if_nameindex(void);

void if_freenameindex(struct if_nameindex *ptr);

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

if_nameindex()：返回动态分配的struct if_nameindex结构数组，数组中的每一个元素分别对应一个本地网络接口；struct if_nameindex结构的if_index字段为接口索引，if_name字段为接口名称字符串；索引为0且名称字符串为NULL表示结构数组的末尾；调用出错时，返回NULL，并将errno设置为相应的值

if_freenameindex()：通过if_nameindex()获取完毕接口名称与索引后，调用该函数以释放动态分配的内存区域

以上4个函数在系统的man文档中都可以查看相应的描述，且都是POSIX标准支持的，Linux内核可能未实现这些函数，或已实现但不同于POSIX标准

这些函数的原型声明与定义并未出现在CentOS 6.7的定制内核2.6.32-573.26.1.el6.x86_64以及原版内核2.6.32.5中，而是由系统的glibc-2.12实现：在glibc-2.12.2源码树中，函数的原型声明位于sysdeps/gnu/net/if.h与sysdeps/generic/net/if.h，函数的定义位于sysdeps/unix/sysv/linux/if_index.c中，本质上是对ioctl(2)的SIOCGIFNAME，SIOCGIFCONF，SIOCGIFINDEX等操作以及netlink套接字进行了封装

示例程序

1. if_name_index.c

#include

#include

#include

int main(void)

{

struct if_nameindex *head, *ifni;

ifni = if_nameindex();

head = ifni;

if (head == NULL) {

perror("if_nameindex()");

exit(EXIT_FAILURE);

}

while (ifni->if_index != 0) {

printf("Interfece %d : %s\n", ifni->if_index, ifni->if_name);

ifni++;

}

if_freenameindex(head);

head = NULL;

ifni = NULL;

exit(EXIT_SUCCESS);

}

编译并运行

# gcc if_name_index.c -o if_name_index

# ./if_name_index

Interfece 1 : lo

Interfece 2 : eth0

Interfece 3 : eth1

2. if_index_to_name.c

#include

#include

#include

#include

int main(int argc, char *argv[])

{

if (argc != 2) {

fprintf(stderr, "Usage: %s [interface index]\n", argv[0]);

exit(EXIT_FAILURE);

}

int saved_errno = errno;

char if_name[IFNAMSIZ] = {'\0'};

unsigned int if_index = (unsigned int )atoi(argv[1]);

char *name = if_indextoname(if_index, if_name);

if (name == NULL && errno == ENXIO) {

fprintf(stderr, "Index %d : No such device\n", if_index);

exit(EXIT_FAILURE);

}

errno = saved_errno;

printf("Index %d : %s\n", if_index, if_name);

exit(EXIT_SUCCESS);

}

编译并运行

# gcc if_index_to_name.c -o if_index_to_name

# ./if_index_to_name

Usage: ./if_index_to_name [interface index]

# ./if_index_to_name 1

Index 1 : lo

# ./if_index_to_name 2

Index 2 : eth0

# ./if_index_to_name 3

Index 3 : eth1

# ./if_index_to_name 4

Index 4 : No such device

3. if_name_to_index.c

#include

#include

#include

int main(int argc, char *argv[])

{

if (argc != 2) {

fprintf(stderr, "Usage: %s [interface name]\n", argv[0]);

exit(EXIT_FAILURE);

}

unsigned int if_index;

if_index = if_nametoindex(argv[1]);

if (if_index == 0) {

fprintf(stderr, "Interface %s : No such device\n", argv[1]);

exit(EXIT_FAILURE);

}

printf("Interface %s : %d\n", argv[1], if_index);

exit(EXIT_SUCCESS);

}

编译并运行

# gcc if_name_to_index.c -o if_name_to_index

# ./if_name_to_index eth0

Interface eth0 : 2

# ./if_name_to_index eth3

Interface eth3 : No such device