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NETDEVICE(7)			    Linux Programmer's Manual			     NETDEVICE(7)

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.
	      IFF_LOWER_UP	Driver signals L1 up (since Linux 2.6.17)
	      IFF_DORMANT	Driver signals dormant (since Linux 2.6.17)
	      IFF_ECHO		Echo sent packets (since Linux 2.6.25)

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

       SIOCGIFPFLAGS, SIOCSIFPFLAGS
	      Get  or set extended (private) flags for the device.  ifr_flags contains a bit mask
	      of the following values:

				      Private flags
	      IFF_802_1Q_VLAN	   Interface is 802.1Q VLAN device.
	      IFF_EBRIDGE	   Interface is Ethernet bridging device.
	      IFF_SLAVE_INACTIVE   Interface is inactive bonding slave.
	      IFF_MASTER_8023AD    Interface is 802.3ad bonding master.
	      IFF_MASTER_ALB	   Interface is balanced-alb bonding master.
	      IFF_BONDING	   Interface is a bonding master or slave.
	      IFF_SLAVE_NEEDARP    Interface needs ARPs for validation.
	      IFF_ISATAP	   Interface is RFC4214 ISATAP interface.

	      Setting the extended (private) interface flags is a privileged operation.

       SIOCGIFADDR, SIOCSIFADDR
	      Get or set the address of the device using ifr_addr.  Setting the interface address
	      is  a privileged operation.  For compatibility, only AF_INET addresses are accepted
	      or returned.

       SIOCGIFDSTADDR, SIOCSIFDSTADDR
	      Get or set the destination address of a point-to-point  device  using  ifr_dstaddr.
	      For  compatibility,  only  AF_INET addresses are accepted or returned.  Setting the
	      destination address is a privileged operation.

       SIOCGIFBRDADDR, SIOCSIFBRDADDR
	      Get or set the broadcast address for a device using ifr_brdaddr.	 For  compatibil-
	      ity,  only  AF_INET  addresses  are  accepted  or  returned.  Setting the broadcast
	      address is a privileged operation.

       SIOCGIFNETMASK, SIOCSIFNETMASK
	      Get or set the network mask for a device	using  ifr_netmask.   For  compatibility,
	      only  AF_INET  addresses	are  accepted or returned.  Setting the network mask is a
	      privileged operation.

       SIOCGIFMETRIC, SIOCSIFMETRIC
	      Get or set the metric of the device using ifr_metric.  This is currently not imple-
	      mented; 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 ker-
	      nel 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 contains the ARPHRD_* device type,
	      sa_data the L2 hardware address starting from byte 0.  Setting the hardware address
	      is a privileged operation.

       SIOCSIFHWBROADCAST
	      Set  the	hardware broadcast address of a device from ifr_hwaddr.  This is a privi-
	      leged operation.

       SIOCGIFMAP, SIOCSIFMAP
	      Get or set the interface's hardware parameters using ifr_map.  Setting the  parame-
	      ters 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  fil-
	      ters 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 allowed only 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 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  buf-
	      fer  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 and the other ioctls that accept	or  return  only  AF_INET
       socket addresses, are IP specific and belong 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  pro-
       gram 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 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

Linux					    2012-04-26				     NETDEVICE(7)
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