Linux提供了一系列网络接口操作相关的命令集,其中,一些传统的工具,如net-tools软件包中的ifconfig(8),arp(8),route(8)等都是通过ioctl(2)系统调用实现
本篇介绍使用ioctl(2)进行网络接口参数的获取与设置
函数原型
#include <sys/ioctl.h>
int ioctl(int d, int request, ...);
第一个参数fd指定一个由open(2)/socket(2)创建的文件描述符
第二个参数request指定操作的类型,即对该文件描述符执行何种操作
第三个参数为一块内存区域,通常依赖于request指定的操作类型
接口参数与操作的相关定义
内核版本:2.6.32.5
ioctl(2)使用struct ifreq与/或struct ifconf结构执行网络接口相关的操作,这两个结构的地址作为ioctl(2)的第三个参数
/* include/linux/if.h */
#define IFNAMSIZ 16
#define IFALIASZ 256
struct ifreq
{
#define IFHWADDRLEN 6
union
{
char ifrn_name[IFNAMSIZ];
} ifr_ifrn;
union {
struct sockaddr ifru_addr;
struct sockaddr ifru_dstaddr;
struct sockaddr ifru_broadaddr;
struct sockaddr ifru_netmask;
struct sockaddr ifru_hwaddr;
short ifru_flags;
int ifru_ivalue;
int ifru_mtu;
struct ifmap ifru_map;
char ifru_slave[IFNAMSIZ];
char ifru_newname[IFNAMSIZ];
void __user * ifru_data;
struct if_settings ifru_settings;
} ifr_ifru;
};
#define ifr_name ifr_ifrn.ifrn_name /* interface name */
#define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */
#define ifr_addr ifr_ifru.ifru_addr /* address */
#define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-p lnk */
#define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */
#define ifr_netmask ifr_ifru.ifru_netmask /* interface net mask */
#define ifr_flags ifr_ifru.ifru_flags /* flags */
#define ifr_metric ifr_ifru.ifru_ivalue /* metric */
#define ifr_mtu ifr_ifru.ifru_mtu /* mtu */
#define ifr_map ifr_ifru.ifru_map /* device map */
#define ifr_slave ifr_ifru.ifru_slave /* slave device */
#define ifr_data ifr_ifru.ifru_data /* for use by interface */
#define ifr_ifindex ifr_ifru.ifru_ivalue /* interface index */
#define ifr_bandwidth ifr_ifru.ifru_ivalue /* link bandwidth */
#define ifr_qlen ifr_ifru.ifru_ivalue /* Queue length */
#define ifr_newname ifr_ifru.ifru_newname /* New name */
#define ifr_settings ifr_ifru.ifru_settings /* Device/proto settings*/
struct ifconf
{
int ifc_len;
union
{
char __user *ifcu_buf;
struct ifreq __user *ifcu_req;
} ifc_ifcu;
};
#define ifc_buf ifc_ifcu.ifcu_buf /* buffer address */
#define ifc_req ifc_ifcu.ifcu_req /* array of structures */
操作类型,ioctl(2)的第二个参数
/* include/linux/sockios.h */
/* Socket configuration controls. */
#define SIOCGIFNAME 0x8910 /* get iface name */
#define SIOCSIFLINK 0x8911 /* set iface channel */
#define SIOCGIFCONF 0x8912 /* get iface list */
#define SIOCGIFFLAGS 0x8913 /* get flags */
#define SIOCSIFFLAGS 0x8914 /* set flags */
#define SIOCGIFADDR 0x8915 /* get PA address */
#define SIOCSIFADDR 0x8916 /* set PA address */
#define SIOCGIFDSTADDR 0x8917 /* get remote PA address */
#define SIOCSIFDSTADDR 0x8918 /* set remote PA address */
#define SIOCGIFBRDADDR 0x8919 /* get broadcast PA address */
#define SIOCSIFBRDADDR 0x891a /* set broadcast PA address */
#define SIOCGIFNETMASK 0x891b /* get network PA mask */
#define SIOCSIFNETMASK 0x891c /* set network PA mask */
#define SIOCGIFMETRIC 0x891d /* get metric */
#define SIOCSIFMETRIC 0x891e /* set metric */
#define SIOCGIFMEM 0x891f /* get memory address (BSD) */
#define SIOCSIFMEM 0x8920 /* set memory address (BSD) */
#define SIOCGIFMTU 0x8921 /* get MTU size */
#define SIOCSIFMTU 0x8922 /* set MTU size */
#define SIOCSIFNAME 0x8923 /* set interface name */
#define SIOCSIFHWADDR 0x8924 /* set hardware address */
#define SIOCGIFENCAP 0x8925 /* get/set encapsulations */
#define SIOCSIFENCAP 0x8926
#define SIOCGIFHWADDR 0x8927 /* Get hardware address */
#define SIOCGIFSLAVE 0x8929 /* Driver slaving support */
#define SIOCSIFSLAVE 0x8930
#define SIOCADDMULTI 0x8931 /* Multicast address lists */
#define SIOCDELMULTI 0x8932
#define SIOCGIFINDEX 0x8933 /* name -> if_index mapping */
#define SIOGIFINDEX SIOCGIFINDEX /* misprint compatibility :-) */
#define SIOCSIFPFLAGS 0x8934 /* set/get extended flags set */
#define SIOCGIFPFLAGS 0x8935
#define SIOCDIFADDR 0x8936 /* delete PA address */
#define SIOCSIFHWBROADCAST 0x8937 /* set hardware broadcast addr */
#define SIOCGIFCOUNT 0x8938 /* get number of devices */
...
#define SIOCETHTOOL 0x8946 /* Ethtool interface */
结构字段与操作类型的含义在大都在注释中已注明
一般步骤
通过ioctl(2)执行网络接口参数的获取/设置的一般步骤为:
通过socket(2)创建IP套接字;由于ioctl(2)此时是与内核通信,因此对套接字的通信域与类型没有强制要求,通信域可以为AF_INET/AF_LOCAL,类型可以为SOCK_DGRAM/SOCK_STREAM/SOCK_RAW等
初始化struct ifconf与/或struct ifreq结构
对套接字描述符调用ioctl(2),执行相应类型的SIO操作
获取返回至truct ifconf与/或struct ifreq结构中的相关信息
示例程序
本地网络接口信息:eth0网线已连接且已配置IPv4地址,eth1网线未连接且未配置IPv4地址
# ip l
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:ed:9d:28 brd ff:ff:ff:ff:ff:ff
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
link/ether 00:0c:29:ed:9d:32 brd ff:ff:ff:ff:ff:ff
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:ed:9d:28 brd ff:ff:ff:ff:ff:ff
inet 192.168.56.139/24 brd 192.168.56.255 scope global eth0
inet6 fe80::20c:29ff:feed:9d28/64 scope link
valid_lft forever preferred_lft forever
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
link/ether 00:0c:29:ed:9d:32 brd ff:ff:ff:ff:ff:ff
1 . 通过SIOCGIFCONF操作获取系统中所有的网络接口
/* list_network_interfaces_ioctl.c */
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <string.h>
#define BUFSIZE 1024
int main(int argc, char *argv[])
{
int sfd, if_count, i;
struct ifconf ifc;
struct ifreq ifr[10];
char ipaddr[INET_ADDRSTRLEN] = {'\0'};
memset(&ifc, 0, sizeof(struct ifconf));
sfd = socket(AF_INET, SOCK_DGRAM, 0);
ifc.ifc_len = 10 * sizeof(struct ifreq);
ifc.ifc_buf = (char *)ifr;
/* SIOCGIFCONF is IP specific. see netdevice(7) */
ioctl(sfd, SIOCGIFCONF, (char *)&ifc);
if_count = ifc.ifc_len / (sizeof(struct ifreq));
for (i = 0; i < if_count; i++) {
printf("Interface %s : ", ifr[i].ifr_name);
inet_ntop(AF_INET,
&(((struct sockaddr_in *)&(ifr[i].ifr_addr))->sin_addr),
ipaddr, INET_ADDRSTRLEN);
printf("%s\n", ipaddr);
}
close(sfd);
exit(EXIT_SUCCESS);
}
编译并运行
# gcc list_network_interfaces_ioctl.c -g -o list_network_interfaces_ioctl
# ./list_network_interfaces_ioctl
Interface lo : 127.0.0.1
Interface eth0 : 192.168.56.139
SIOCGIFCONF操作需要同时使用struct ifconf与struct ifreq
初始化struct ifconf时,ifc_ifcu指定一个缓冲区的首地址,缓冲区中保存若干个连续的struct ifreq,ifc_len指定该缓冲区的长度;ioctl(2)返回后,内核将为每一个配置了IPv4地址的本地网络接口分配一个struct ifreq并保存到初始化的缓冲区中,struct ifreq中保存单个网络接口的名称及IPv4地址,struct ifconf的ifc_len被更新为初始化缓冲区中实际返回的数据长度
2 . 通过SIOCGIFADDR操作获取指定网络接口的IPv4地址
/* get_interface_ip_address_ioctl.c */
#include <stdio.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
static char *get_ipaddr(const char *);
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Usage: %s [network interface name]\n", argv[0]);
exit(EXIT_FAILURE);
}
char ifname[IFNAMSIZ] = {'\0'};
strncpy(ifname, argv[1], IFNAMSIZ-1);
char *ip = get_ipaddr(ifname);
printf("Interface %s : %s\n", ifname, ip);
return 0;
}
static char *get_ipaddr(const char *dev)
{
int sfd, saved_errno, ret;
struct ifreq ifr;
char *ipaddr;
ipaddr = (char *)malloc(INET_ADDRSTRLEN);
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_addr.sa_family = AF_INET;
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
sfd = socket(AF_INET, SOCK_DGRAM, 0);
errno = saved_errno;
ret = ioctl(sfd, SIOCGIFADDR, &ifr);
if (ret == -1) {
if (errno == 19) {
fprintf(stderr, "Interface %s : No such device.\n", dev);
exit(EXIT_FAILURE);
}
if (errno == 99) {
fprintf(stderr, "Interface %s : No IPv4 address assigned.\n", dev);
exit(EXIT_FAILURE);
}
}
saved_errno = errno;
inet_ntop(AF_INET, &(((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr), ipaddr, INET_ADDRSTRLEN);
close(sfd);
return ipaddr;
}
编译并运行
# gcc get_interface_ip_address_ioctl.c -g -o get_interface_ip_address_ioctl
#
# ./get_interface_ip_address_ioctl eth0
Interface eth0 : 192.168.56.139
#
# ./get_interface_ip_address_ioctl eth1
Interface eth1 : No IPv4 address assigned.
#
# ./get_interface_ip_address_ioctl eth2
Interface eth2 : No such device.
SIOCGIFADDR操作使用struct ifreq中的ifr_ifru.ifru_addr字段;ifr_ifrn.ifrn_name指定为网络接口名称并调用ioctl(SIOCGIFADDR),返回后将ifr_ifru.ifru_addr转换为IPv4套接字地址结构,IPv4地址保存在该结构中的sin_addr字段中
SIOCGIFCONF与SIOCGIFADDR属于IPv4特定的操作,对于未配置IPv4地址的网络接口,ioctl(SIOCGIFCONF)返回时不会分配struct ifreq结构,因而不会返回该接口的名称,而ioctl(SIOCGIFADDR)将以errno值99(Cannot assign requested address)而调用失败
若指定了系统中不存在的网络接口,则errno的值为19(No such device)
SIOCGIFCONF与SIOCGIFADDR无法获取网络接口的IPv6地址,ioctl的内核源码中通过读取/proc/net/if_inet6获取
3 . 通过SIOCGIFHWADDR操作获取指定网络接口的mac地址
/* get_interface_mac_address_ioctl.c */
#include <stdio.h>
#include <stdlib.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <string.h>
#include <netinet/if_ether.h>
#include <net/if_arp.h>
static unsigned char *get_if_mac(const char *);
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Usage: %s [network interface name]\n", argv[0]);
exit(EXIT_FAILURE);
}
char ifname[IFNAMSIZ] = {'\0'};
strncpy(ifname, argv[1], IFNAMSIZ-1);
unsigned char *mac = get_if_mac(ifname);
printf("Interface %s : %.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n",
ifname, *mac, *(mac+1), *(mac+2), *(mac+3), *(mac+4), *(mac+5));
return 0;
}
static unsigned char *get_if_mac(const char *dev)
{
int sfd, ret, saved_errno, i;
unsigned char *mac_addr;
struct ifreq ifr;
mac_addr = (unsigned char *)malloc(ETH_ALEN);
sfd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
saved_errno = errno;
ret = ioctl(sfd, SIOCGIFHWADDR, &ifr);
if (ret == -1 && errno == 19) {
fprintf(stderr, "Interface %s : No such device.\n", dev);
exit(EXIT_FAILURE);
}
errno = saved_errno;
if (ifr.ifr_addr.sa_family == ARPHRD_LOOPBACK) {
printf("Interface %s : A Loopback device.\n", dev);
printf("MAC address is always 00:00:00:00:00:00\n");
exit(EXIT_SUCCESS);
}
if (ifr.ifr_addr.sa_family != ARPHRD_ETHER) {
fprintf(stderr, "Interface %s : Not an Ethernet device.\n", dev);
exit(EXIT_FAILURE);
}
memcpy(mac_addr, ifr.ifr_hwaddr.sa_data, ETH_ALEN);
return (unsigned char *)mac_addr;
}
编译并运行
# gcc get_interface_mac_address_ioctl.c -g -o get_interface_mac_address_ioctl
#
# ./get_interface_mac_address_ioctl lo
Interface lo : A Loopback device.
MAC address is always 00:00:00:00:00:00
#
# ./get_interface_mac_address_ioctl eth0
Interface eth0 : 00:0c:29:ed:9d:28
#
# ./get_interface_mac_address_ioctl eth1
Interface eth1 : 00:0c:29:ed:9d:32
#
# ./get_interface_mac_address_ioctl eth2
Interface eth2 : No such device.
SIOCGIFHWADDR操作使用struct ifreq中的ifr_ifru.ifru_hwaddr字段,在ifr_ifrn.ifrn_name中填充指定的网络接口名称后,该接口的mac地址按顺序返回到ifr_ifru.ifru_hwaddr.sa_data数组的前6个字节中
4 . 通过SIOCGIFFLAGS操作获取指定网络接口的标志
/* get_interface_flags_ioctl.c */
#include <stdio.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <netinet/if_ether.h>
#include <net/if_arp.h>
static short get_if_flags(int, char *);
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Usage: %s [network interface name]\n", argv[0]);
exit(EXIT_FAILURE);
}
int sfd;
short flags;
char ifname[IFNAMSIZ] = {'\0'};
strncpy(ifname, argv[1], IFNAMSIZ-1);
sfd = socket(AF_INET, SOCK_DGRAM, 0);
flags = get_if_flags(sfd, ifname);
printf("Interface %s : ", ifname);
if (flags & IFF_UP)
printf("UP ");
if (flags & IFF_RUNNING)
printf("RUNNING ");
if (flags & IFF_LOOPBACK)
printf("LOOPBACK ");
if (flags & IFF_BROADCAST)
printf("BROADCAST ");
if (flags & IFF_MULTICAST)
printf("MULTICAST ");
if (flags & IFF_PROMISC)
printf("PROMISC");
#ifndef IFF_LOWER_UP
#define IFF_LOWER_UP 0x10000
if (flags & IFF_LOWER_UP)
printf("LOWER_UP");
#endif
printf("\n");
close(sfd);
exit(EXIT_SUCCESS);
}
static short get_if_flags(int s, char *dev)
{
int saved_errno, ret;
short if_flags;
struct ifreq ifr;
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
saved_errno = errno;
ret = ioctl(s, SIOCGIFFLAGS, &ifr);
if (ret == -1 && errno == 19) {
fprintf(stderr, "Interface %s : No such device.\n", dev);
exit(EXIT_FAILURE);
}
errno = saved_errno;
if_flags = ifr.ifr_flags;
return if_flags;
}
编译并运行
# gcc get_interface_flags_ioctl.c -g -o get_interface_flags_ioctl
#
# ./get_interface_flags_ioctl lo
Interface lo : UP RUNNING LOOPBACK
#
# ./get_interface_flags_ioctl eth0
Interface eth0 : UP RUNNING BROADCAST MULTICAST
#
# ./get_interface_flags_ioctl eth1
Interface eth1 : UP BROADCAST MULTICAST
#
# ./get_interface_flags_ioctl eth2
Interface eth2 : No such device.
ifr_ifrn.ifrn_name指定为网络接口名称后,ioctl(SIOCGIFFLAGS)调用将标志返回到ifr_ifru.ifru_flags字段
IFF_RUNNING表示该接口已被激活,且可以正常传输数据
IFF_UP表示giant接口已被激活,但可能无法正常传输数据,如网线未连接的情况
IFF_LOWER_UP表示网络的物理连接已就绪,即网线连接正常;由于struct ifreq的ifr_ifru.ifru_flags类型为short,用16进制表示仅为4位,因而无法获取与设置5位16进制的IFF_LOWER_UP标志(0x10000)
5 .通过SIOCSIFADDR操作设置指定网络接口的IPv4地址
/* set_interface_ip_address_ioctl.c */
#include <stdio.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
static void set_ipaddr(const char *, const char *);
int main(int argc, char *argv[])
{
if (argc != 3) {
fprintf(stderr, "Usage: %s [network interface name] [ip address]\n",
argv[0]);
exit(EXIT_FAILURE);
}
char ifname[IFNAMSIZ] = {'\0'};
strncpy(ifname, argv[1], IFNAMSIZ-1);
char ipaddr[INET_ADDRSTRLEN] = {'\0'};
strncpy(ipaddr, argv[2], INET_ADDRSTRLEN);
set_ipaddr(ifname, ipaddr);
printf("Interface %s : ip address is set to %s\n", ifname, ipaddr);
return 0;
}
static void set_ipaddr(const char *dev, const char *ip)
{
int sfd, saved_errno, ret;
struct ifreq ifr;
struct sockaddr_in sin;
sfd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
inet_pton(AF_INET, ip, &(sin.sin_addr));
memcpy(&ifr.ifr_addr, &sin, sizeof(struct sockaddr));
errno = saved_errno;
ret = ioctl(sfd, SIOCSIFADDR, &ifr);
if (ret == -1) {
if (errno == 19) {
fprintf(stderr, "Interface %s : No such device.\n", dev);
exit(EXIT_FAILURE);
}
if (errno == 99) {
fprintf(stderr, "Interface %s : No IPv4 address assigned.\n", dev);
exit(EXIT_FAILURE);
}
}
saved_errno = errno;
close(sfd);
}
编译并运行
# gcc set_interface_ip_address_ioctl.c -g -o set_interface_ip_address_ioctl
#
# ./set_interface_ip_address_ioctl eth1 10.0.0.1
Interface eth1 : ip address is set to 10.0.0.1
#
# ./get_interface_ip_address_ioctl eth1
Interface eth1 : 10.0.0.1
#
# ./set_interface_ip_address_ioctl eth1 10.0.0.2
Interface eth1 : ip address is set to 10.0.0.2
#
# ./get_interface_ip_address_ioctl eth1
Interface eth1 : 10.0.0.2
与ifconfig(8)相同,多次指定同一网络接口名称设置IP地址时,最后的设置将覆盖先前的设置而生效
6 . 通过SIOCGIFFLAGS操作设置指定网络接口的标志
使用ifconfig(8)将eth1设置为混杂模式,并关闭该接口,然后在程序中关闭混杂模式,并开启该接口
# ifconfig eth1 promisc
#
# ifconfig eth1 down
#
# ./get_interface_flags_ioctl eth1
Interface eth1 : BROADCAST MULTICAST PROMISC
/* set_interface_flags_ioctl.c */
#include <stdio.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
static short get_if_flags(int, struct ifreq*);
static void set_if_flags(int, struct ifreq*);
int main(int argc, char *argv[])
{
if (argc != 2) {
fprintf(stderr, "Usage: %s [network interface name]\n", argv[0]);
exit(EXIT_FAILURE);
}
int sfd;
short flags;
struct ifreq ifr;
char ifname[IFNAMSIZ] = {'\0'};
strncpy(ifname, argv[1], IFNAMSIZ-1);
sfd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
flags = get_if_flags(sfd, &ifr);
ifr.ifr_flags = flags;
/* set IFF_UP if cleared */
if (!(flags & IFF_UP)) {
ifr.ifr_flags |= IFF_UP;
set_if_flags(sfd, &ifr);
printf("Interface %s : UP set.\n", ifname);
}
flags = ifr.ifr_flags;
/* clear IFF_PROMISC if set */
if (flags & IFF_PROMISC) {
ifr.ifr_flags &= ~IFF_PROMISC;
set_if_flags(sfd, &ifr);
printf("Interface %s : PROMISC cleared.\n", ifname);
}
close(sfd);
exit(EXIT_SUCCESS);
}
static short get_if_flags(int s, struct ifreq *ifr)
{
int ret, saved_errno;
short if_flags;
saved_errno = errno;
ret = ioctl(s, SIOCGIFFLAGS, ifr);
if (ret == -1 && errno == 19) {
fprintf(stderr, "Interface %s : No such device.\n", ifr->ifr_name);
exit(EXIT_FAILURE);
}
errno = saved_errno;
if_flags = ifr->ifr_flags;
return if_flags;
}
static void set_if_flags(int s, struct ifreq *ifr)
{
int ret, saved_errno;
saved_errno = errno;
ret = ioctl(s, SIOCSIFFLAGS, ifr);
if (ret == -1) {
fprintf(stderr, "Interface %s : %s\n", ifr->ifr_name, strerror(errno));
exit(EXIT_FAILURE);
}
errno = saved_errno;
}
编译并运行
# gcc set_interface_flags_ioctl.c -g -o set_interface_flags_ioctl
#
# ./set_interface_flags_ioctl eth1
Interface eth1 : UP set.
Interface eth1 : PROMISC cleared.
#
# ./get_interface_flags_ioctl eth1
Interface eth1 : UP BROADCAST MULTICAST
7 .通过SIOCSIFNAME操作更改网络接口的名称
/* change_ifname_ioctl.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
static void change_ifname(char *, char *);
static void shutdown_if_up(char *);
int main(int argc, char *argv[])
{
if (argc != 3) {
fprintf(stderr, "%s [old ifname] [new ifname]\n", argv[0]);
exit(EXIT_FAILURE);
}
char old_ifname[IFNAMSIZ] = {'\0'};
strncpy(old_ifname, argv[1], IFNAMSIZ);
char new_ifname[IFNAMSIZ] = {'\0'};
strncpy(new_ifname, argv[2], IFNAMSIZ);
change_ifname(old_ifname, new_ifname);
printf("Interface name %s has been changed to %s\n", old_ifname, new_ifname);
return 0;
}
void change_ifname(char *old_dev, char *new_dev)
{
int sfd, ret, saved_errno;
struct ifreq ifr;
shutdown_if_up(old_dev);
sfd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, old_dev, IFNAMSIZ);
strncpy(ifr.ifr_newname, new_dev, IFNAMSIZ);
saved_errno = errno;
ret = ioctl(sfd, SIOCSIFNAME, &ifr);
if (ret == -1) {
fprintf(stderr, "Interface %s : %s\n", dev, strerror(errno));
exit(EXIT_FAILURE);
}
errno = saved_errno;
}
static void shutdown_if_up(char *dev)
{
int sfd, ret, saved_errno;
short flags;
struct ifreq ifr;
sfd = socket(AF_INET, SOCK_DGRAM, 0);
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, dev, IFNAMSIZ);
saved_errno = errno;
ret = ioctl(sfd, SIOCGIFFLAGS, &ifr);
if (ret == -1) {
fprintf(stderr, "Interface %s : %s\n", dev, strerror(errno));
exit(EXIT_FAILURE);
}
errno = saved_errno;
flags = ifr.ifr_flags;
if (flags & IFF_UP) {
ifr.ifr_flags &= ~IFF_UP;
saved_errno = errno;
ret = ioctl(sfd, SIOCSIFFLAGS, &ifr);
if (ret == -1) {
fprintf(stderr, "Interface %s : %s\n",dev, strerror(errno));
exit(EXIT_FAILURE);
}
errno = saved_errno;
}
}
将struct ifreq的ifr_ifrn.ifrn_name指定为网络接口名称后,ioctl(SIOCSIFNAME)将指定的新名称写入到ifr_ifru.ifru_newname中;该操作要求网络接口为关闭状态,即(~IFF_UP)
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