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RedHat 9 (Linux i386) - man page for netdevice (redhat section 7)

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

       netdevice - Low level access to Linux network devices.

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

       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.

       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.

	      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.

	      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

	      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.

	      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

	      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.

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

	      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

	      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

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

	      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.

	      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  no

       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.

       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).

       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

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

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

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