NETDEVICE Section: Linux Programmer's Manual (7) Updated: 2 May 2025 Index   NAME netdevice - Low level access to Linux network devices.   SYNOPSIS #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. They 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 ioctl 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 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 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. Setting the active flag word is a privileged operation, but any process may read it. 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. SIOCGIFHWADDR, SIOCSIFHWADDR Get or set the hardware address of a device using ifr_hwaddr. 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. 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_ifindex to ifr_newname. This is a privileged operation. Most protocols support their own ioctls to configure protocol specific interface options. See the protocol man pages for a description. In addition some devices support private ioctls. These are not described here.   Index NAME SYNOPSIS DESCRIPTION IOCTLS This document was created by using the manual pages. Time: 12:14:03 GMT, March 24, 2025