Linux Get network interface information

Linux acquires network interface information needed for the function of the IOCTL (), struct struct ifreq,struct ifconf

1.ioctl () function prototypes and functions

1 #include <sys/ioctl.h>2  3int ioctl (intint  Request, ...); 4 5 // Parameters 6 // int D: is a file descriptor 7 // int Request: Represents the information to be requested. such as IP address, netmask, etc 8//...: variable parameters, depending on request

Here is the request parameter for the IOCTL requests and the data type that the ARG address must point to:

2.struct Ifreq Structural Body

This structure is defined in include/net/if.h, which is used to configure IP addresses, activate interfaces, configure interface information such as MTU

1  /*INTERFACE request structure used for socket IOCTL ' s. All Interface2 The IOCTL ' s must has parameter definitions which begin with Ifr_name.3 The remainder may interface specific. */4  5 structIfreq6 {7# define Ifhwaddrlen68 # define Ifnamsiz if_namesize9 UnionTen        { One      CharIfrn_name[ifnamsiz];/*Interface name, e.g. "En0". */ A } IFR_IFRN; -   - Union the        { -      structsockaddr ifru_addr; -      structsockaddr ifru_dstaddr; -      structsockaddr ifru_broadaddr; +      structsockaddr Ifru_netmask; -      structsockaddr ifru_hwaddr; +       Short intifru_flags; A      intIfru_ivalue; at      intIfru_mtu; -      structIfmap Ifru_map; -      CharIfru_slave[ifnamsiz];/*Just fits the size*/ -      CharIfru_newname[ifnamsiz]; - __caddr_t Ifru_data; - } Ifr_ifru; in    }; -# define Ifr_name Ifr_ifrn.ifrn_name/*Interface Name*/ to# 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. lnk*/ the# 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*/Panax Notoginseng# define Ifr_metric Ifr_ifru.ifru_ivalue/*Metric*/ -# define IFR_MTU IFR_IFRU.IFRU_MTU/*MTU*/ the# define IFR_MAP Ifr_ifru.ifru_map/*Device Map*/ +# define Ifr_slave Ifr_ifru.ifru_slave/*slave Device*/ A# define Ifr_data Ifr_ifru.ifru_data/*For use by interface*/ the# 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 _iot_ifreq _iot (_iots (Char), Ifnamsiz,_iots (Char), -,0,0) -# define _iot_ifreq_short _iot (_iots (Char), Ifnamsiz,_iots ( Short),1,0,0) -# define _iot_ifreq_int _iot (_iots (Char), Ifnamsiz,_iots (int),1,0,0)

3.struct ifconf

The ifreq is included in the ifconf structure. The ifconf structure is usually used to hold information about all interfaces.

1  /*Structure used in siocgifconf request. Used to retrieve interface2 configuration for machine (useful-programs which must know all3 networks accessible). */4  5  structifconf6    {7      intIfc_len;/*Size of buffer. */8 Union9        {Ten __caddr_t ifcu_buf; One      structIfreq *Ifcu_req; A } IFC_IFCU; -    }; -# define IFC_BUF Ifc_ifcu.ifcu_buf/*Buffer address. */ the# define Ifc_req Ifc_ifcu.ifcu_req/*Array of structures. */ -# define _IOT_IFCONF _iot (_iots (structifconf),1,0,0,0,0)/* Not right*/ -  #endif/* Misc. */

The following program is to get the IP address of this machine

1#include <stdio.h>2#include <sys/socket.h>3#include <string.h>4#include <sys/types.h>5#include <netinet/inch.h>6#include <sys/ioctl.h>7#include <net/if.h>8 9 //#define ETH_NAME "eth0"Ten //#define NET_NAME "Wlan1" One  A intMainintargcChar*argv[]) - { -     if(ARGC! =2) { theprintf"using%s <eth_name>\n", argv[0]); -         return 0; -     } -  +     intSock =0; -     structsockaddr_in sin; +     structIfreq IFR;//information to save the interface A  atSock = socket (af_inet, SOCK_DGRAM,0); -     if(Sock = =-1) { -Perror ("Socket"); -         return 1; -     } -  instrcpy (Ifr.ifr_name, argv[1]); -     intRET = IOCTL (sock, SIOCGIFADDR, &AMP;IFR);//siocgifaddr Get interface address to     if(Ret <0) { +Perror ("IOCTL"); -         return 1; the     }     *  $memcpy (&sin, &AMP;IFR.IFR_ADDR,sizeof(sin));//Copy the address to the SOCKADDR_IN structurePanax Notoginsengprintf"%s\n", Inet_ntoa (SIN.SIN_ADDR));//Show -     return 0;  the      +}

The results of the operation are as follows:

Linux Get network interface information