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NAME    [Toc]    [Back]

       netdevice - Low level access to Linux network devices.

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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 sockaddrifr_addr;
		   struct sockaddrifr_dstaddr;
		   struct sockaddrifr_broadaddr;
		   struct sockaddrifr_netmask;
		   struct sockaddrifr_hwaddr;
		   short   ifr_flags;
		   int	   ifr_ifindex;
		   int	   ifr_metric;
		   int	   ifr_mtu;
		   struct ifmapifr_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    [Toc]    [Back]

       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    [Toc]    [Back]
	      Given the ifr_ifindex, return  the  name	of  the  interface  in
	      ifr_name.   This	is  the only ioctl which returns its result in

       SIOCGIFINDEX    [Toc]    [Back]
	      Retrieve the interface index of the interface into  ifr_ifindex.

	      Get  or  set the active flag word of the device.	ifr_flags contains
 a bitmask 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

	      Setting  the active flag word is a privileged operation, but any
	      process may read it.

	      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

	      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.

	      Get  or  set  the hardware address of a device using ifr_hwaddr.
	      The hardware address is specified in a struct sockaddr.  sa_fam-
	      ily  contains  the ARPHRD_* device type, sa_data the L2 hardware
	      address starting from byte 0.  Setting the hardware address is a
	      privileged operation.

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

	      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.

	      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.

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

       SIOCSIFNAME    [Toc]    [Back]
	      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    [Toc]    [Back]
	      Return  a  list  of  interface (transport layer) addresses. This
	      currently means only addresses of the AF_INET (IPv4) family  for
	      compatibility.   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 no 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    [Toc]    [Back]

       Strictly seen, 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    [Toc]    [Back]

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

	      #ifndef ifr_newname
	      #define ifr_newname     ifr_ifru.ifru_slave

SEE ALSO    [Toc]    [Back]

       ip(7), proc(7), rtnetlink(7)

Linux Man Page			  1999-05-02			  NETDEVICE(7)
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