Linux 获取本机IP地址和MAC地址（二）

NAME
       netdevice - Low level access to Linux network devices

SYNOPSIS
       #include <sys/ioctl.h>
       #include <net/if.h>

DESCRIPTION
       This man page describes the sockets interface which is used to configure network devices.

       Linux  supports some standard ioctls to configure network devices.  They can be used on any socket’s file descriptor regardless of the family or
       type.  They pass an ifreq structure:

struct ifreq {               char ifr_name[IFNAMSIZ]; /* Interface name */               union {                   struct sockaddr ifr_addr;                   struct sockaddr ifr_dstaddr;                   struct sockaddr ifr_broadaddr;                   struct sockaddr ifr_netmask;                   struct sockaddr ifr_hwaddr;                   short           ifr_flags;                   int             ifr_ifindex;                   int             ifr_metric;                   int             ifr_mtu;                   struct ifmap    ifr_map;                   char            ifr_slave[IFNAMSIZ];                   char            ifr_newname[IFNAMSIZ];                   char           *ifr_data;               };           };           struct ifconf {               int           ifc_len; /* size of buffer */               union {                   char           *ifc_buf; /* buffer address */                   struct ifreq   *ifc_req; /* array of structures */               };

 

            Normally, the user specifies which device to affect by setting ifr_name to the name of the interface.  All other members of  the  structure  may
       share memory.

   Ioctls
       If  an  ioctl is marked as privileged then using it requires an effective user ID of 0 or the CAP_NET_ADMIN capability.  If this is not the case
       EPERM will be returned.

       SIOCGIFNAME
              Given the ifr_ifindex, return the name of the interface in ifr_name.  This is the only ioctl which returns its result in ifr_name.

       SIOCGIFINDEX
              Retrieve the interface index of the interface into ifr_ifindex.

       SIOCGIFFLAGS, SIOCSIFFLAGS
              Get or set the active flag word of the device.  ifr_flags contains a bit mask of the following values:

                                          Device flags
              IFF_UP            Interface is running.
              IFF_BROADCAST     Valid broadcast address set.
              IFF_DEBUG         Internal debugging flag.
              IFF_LOOPBACK      Interface is a loopback interface.
              IFF_POINTOPOINT   Interface is a point-to-point link.
              IFF_RUNNING       Resources allocated.
              IFF_NOARP         No arp protocol, L2 destination address not set.
              IFF_PROMISC       Interface is in promiscuous mode.
              IFF_NOTRAILERS    Avoid use of trailers.
              IFF_ALLMULTI      Receive all multicast packets.
              IFF_MASTER        Master of a load balancing bundle.
              IFF_SLAVE         Slave of a load balancing bundle.
              IFF_MULTICAST     Supports multicast
              IFF_PORTSEL       Is able to select media type via ifmap.
              IFF_AUTOMEDIA     Auto media selection active.
              IFF_DYNAMIC       The addresses are lost  when  the  interface  goes
                                down.
              Setting the active flag word is a privileged operation, but any process may read it.

       SIOCGIFMETRIC, SIOCSIFMETRIC
              Get  or set the metric of the device using ifr_metric.  This is currently not implemented; it sets ifr_metric to 0 if you attempt to read
       it and returns EOPNOTSUPP if you attempt to set it.

       SIOCGIFMTU, SIOCSIFMTU
              Get or set the MTU (Maximum Transfer Unit) of a device using ifr_mtu.  Setting the MTU is a privileged operation.  Setting the MTU to too
              small values may cause kernel crashes.

       SIOCGIFHWADDR, SIOCSIFHWADDR
              Get  or  set  the hardware address of a device using ifr_hwaddr.  The hardware address is specified in a struct sockaddr.  sa_family con-
              tains the ARPHRD_* device type, sa_data the L2 hardware address starting from byte 0.  Setting the hardware address is a privileged oper-
              ation.

       SIOCSIFHWBROADCAST
              Set the hardware broadcast address of a device from ifr_hwaddr.  This is a privileged operation.

       SIOCGIFMAP, SIOCSIFMAP
              Get or set the interface’s hardware parameters using ifr_map.  Setting the parameters is a privileged operation.

                  struct ifmap {
                      unsigned long   mem_start;
                      unsigned long   mem_end;
                      unsigned short  base_addr;
                      unsigned char   irq;
                      unsigned char   dma;
                      unsigned char   port;
                  };

              The interpretation of the ifmap structure depends on the device driver and the architecture.

       SIOCADDMULTI, SIOCDELMULTI
              Add an address to or delete an address from the device’s link layer multicast filters using ifr_hwaddr.  These are privileged operations.
              See also packet(7) for an alternative.

       SIOCGIFTXQLEN, SIOCSIFTXQLEN
              Get or set the transmit queue length of a device using ifr_qlen.  Setting the transmit queue length is a privileged operation.

       SIOCSIFNAME
              Changes the name of the interface specified in ifr_name to ifr_newname.  This is a privileged operation.  It is  only  allowed  when  the
              interface is not up.
 SIOCGIFCONF
              Return a list of interface (transport layer) addresses.  This currently means only addresses of the AF_INET (IPv4) family for compatibil-
              ity.  The user passes a ifconf structure as argument to the ioctl.  It contains a pointer to an array of ifreq structures in ifc_req  and
              its  length in bytes in ifc_len.  The kernel fills the ifreqs with all current L3 interface addresses that are running: ifr_name contains
              the interface name (eth0:1 etc.), ifr_addr the address.  The kernel returns with the actual length in ifc_len.  If ifc_len  is  equal  to
              the  original  length  the  buffer probably has overflowed and you should retry with a bigger buffer to get all addresses.  When no error
              occurs the ioctl returns 0; otherwise -1.  Overflow is not an error.

       Most protocols support their own ioctls to configure protocol-specific interface options.  See the protocol man pages for  a  description.   For
       configuring IP addresses see ip(7).

       In addition some devices support private ioctls.  These are not described here.

NOTES
       Strictly speaking, SIOCGIFCONF is IP specific and belongs in ip(7).

       The names of interfaces with no addresses or that don’t have the IFF_RUNNING flag set can be found via /proc/net/dev.

       Local IPv6 IP addresses can be found via /proc/net or via rtnetlink(7).

BUGS
       glibc 2.1 is missing the ifr_newname macro in <net/if.h>.  Add the following to your program as a workaround:

           #ifndef ifr_newname
           #define ifr_newname     ifr_ifru.ifru_slave
           #endif

SEE ALSO
       proc(5), capabilities(7), ip(7), rtnetlink(7)

COLOPHON
       This  page  is part of release 3.09 of the Linux man-pages project.  A description of the project, and information about reporting documentation
       bugs, can be found at http://www.kernel.org/doc/man-pages/.

Linux                             1999-05-02                      NETDEVICE(7)