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 config-
       ure 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.  Most of them 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;
	       };
	   };

       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	effec-
       tive  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  con-
	      tains 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 compati-
	      bility, 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  compatibility,  only	 AF_INET  addresses  are  accepted  or
	      returned.	  Setting the broadcast address is a privileged opera-
	      tion.

       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  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_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
	      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  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.   Unlike  the others, this ioctl passes an ifconf
	      structure:

		  struct ifconf {
		      int		  ifc_len; /* size of buffer */
		      union {
			  char		 *ifc_buf; /* buffer address */
			  struct ifreq	 *ifc_req; /* array of structures */
		      };
		  };

	      If ifc_req is NULL, SIOCGIFCONF  returns	the  necessary	buffer
	      size  in bytes for receiving all available addresses in ifc_len.
	      Otherwise, ifc_req contains a  pointer  to  an  array  of	 ifreq
	      structures  to  be filled with all currently active L3 interface
	      addresses.  ifc_len contains the size of	the  array  in	bytes.
	      Within each ifreq structure, ifr_name will receive the interface
	      name, and ifr_addr the address.	The  actual  number  of	 bytes
	      transferred is returned in ifc_len.

	      If  the  size  specified by ifc_len is insufficient to store all
	      the addresses, the kernel	 will  skip  the  exceeding  ones  and
	      return success.  There is no reliable way of detecting this con-
	      dition once it has occurred.  It	is  therefore  recommended  to
	      either determine the necessary buffer size beforehand by calling
	      SIOCGIFCONF with ifc_req set to NULL, or to retry the call  with
	      a	 bigger	 buffer	 whenever  ifc_len upon return differs by less
	      than sizeof(struct ifreq) from its original value.

	      If an error occurs accessing the	ifconf	or  ifreq  structures,
	      EFAULT will be returned.

       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 fol-
       lowing 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 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2014-01-24			  NETDEVICE(7)