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.
| 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) |
| 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.
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.
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.
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).
#ifndef ifr_newname #define ifr_newname ifr_ifru.ifru_slave #endif