netdevice <root
NETDEVICE(7)                        Linux Programmer's Manual                        NETDEVICE(7)

NAME
       netdevice - low-level access to Linux network devices

SYNOPSIS
       #include 
       #include 

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.  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 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.  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 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 .  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 4.04 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 http://www.kernel.org/doc/man-pages/.

Linux                                       2014-01-24                               NETDEVICE(7)

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