# netdevice

## 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.  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;
                   };
               };
    
           **AF_INET6** is an exception.  It passes an _in6_ifreq_ structure:
    
               struct in6_ifreq {
                   struct in6_addr     ifr6_addr;
                   u32                 ifr6_prefixlen;
                   int                 ifr6_ifindex; /* Interface index */
               };
    
           Normally, the user specifies which device to affect by setting
           _ifr_name_ to the name of the interface or _ifr6_ifindex_ to the index
           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**
           **SIOCDIFADDR**
                  Get, set, or delete the address of the device using
                  _ifr_addr_ , or _ifr6_addr_ with _ifr6_prefixlen_.  Setting or
                  deleting the interface address is a privileged operation.
                  For compatibility, **SIOCGIFADDR** returns only **AF_INET**
                  addresses, **SIOCSIFADDR** accepts **AF_INET** and **AF_INET6**
                  addresses, and **SIOCDIFADDR** deletes only **AF_INET6** addresses.
                  A **AF_INET** address can be deleted by setting it to zero via
                  **SIOCSIFADDR**.
    
           **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 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 (network 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



           **SIOCGIFCONF** and the other ioctls that accept or return only
           **AF_INET** socket addresses are IP-specific and perhaps should rather
           be documented 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_.
    
           **AF_INET6** IPv6 addresses can be read from _/proc/net/if_inet6_ or via
           rtnetlink(7).  Adding a new IPv6 address and deleting an existing
           IPv6 address can be done via **SIOCSIFADDR** and **SIOCDIFADDR** or via
           rtnetlink(7).  Retrieving or changing destination IPv6 addresses
           of a point-to-point interface is possible only 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
    


* * *