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 fam-
       ily 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 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 compatibility, 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 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
	      contains the ARPHRD_* device type, sa_data the L2 hardware address starting from byte 0.	Setting the hardware address is  a  privi-
	      leged 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 opera-
	      tions.  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 com-
	      patibility.  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.  Other-
	      wise,  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 suc-
	      cess.  There is no reliable way of detecting this condition 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 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 4.15 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								    2017-09-15							      NETDEVICE(7)