1NETDEVICE(7) Linux Programmer's Manual NETDEVICE(7)
2
6 netdevice - Low level access to Linux network devices
7
9 #include <sys/ioctl.h>
10 #include <net/if.h>
11
13 This man page describes the sockets interface which is used to config‐
14 ure network devices.
15 Linux supports some standard ioctls to configure network devices. They
17 can be used on any socket's file descriptor regardless of the family or
18 type. They pass an ifreq structure:
19 struct ifreq {
21 char ifr_name[IFNAMSIZ]; /* Interface name */
22 union {
23 struct sockaddr ifr_addr;
24 struct sockaddr ifr_dstaddr;
25 struct sockaddr ifr_broadaddr;
26 struct sockaddr ifr_netmask;
27 struct sockaddr ifr_hwaddr;
28 short ifr_flags;
29 int ifr_ifindex;
30 int ifr_metric;
31 int ifr_mtu;
32 struct ifmap ifr_map;
33 char ifr_slave[IFNAMSIZ];
34 char ifr_newname[IFNAMSIZ];
35 char *ifr_data;
36 };
37 };
38 struct ifconf {
40 int ifc_len; /* size of buffer */
41 union {
42 char *ifc_buf; /* buffer address */
43 struct ifreq *ifc_req; /* array of structures */
44 };
45 };
46 Normally, the user specifies which device to affect by setting ifr_name
48 to the name of the interface. All other members of the structure may
49 share memory.
50 Ioctls
52 If an ioctl is marked as privileged then using it requires an effective
53 user ID of 0 or the CAP_NET_ADMIN capability. If this is not the case
54 EPERM will be returned.
55 SIOCGIFNAME
57 Given the ifr_ifindex, return the name of the interface in
58 ifr_name. This is the only ioctl which returns its result in
59 ifr_name.
60 SIOCGIFINDEX
62 Retrieve the interface index of the interface into ifr_ifindex.
63 SIOCGIFFLAGS, SIOCSIFFLAGS
65 Get or set the active flag word of the device. ifr_flags con‐
66 tains a bit mask of the following values:
67 Device flags
69 IFF_UP Interface is running.
70 IFF_BROADCAST Valid broadcast address set.
71 IFF_DEBUG Internal debugging flag.
72 IFF_LOOPBACK Interface is a loopback interface.
73 IFF_POINTOPOINT Interface is a point-to-point link.
74 IFF_RUNNING Resources allocated.
75 IFF_NOARP No arp protocol, L2 destination address not set.
76 IFF_PROMISC Interface is in promiscuous mode.
77 IFF_NOTRAILERS Avoid use of trailers.
78 IFF_ALLMULTI Receive all multicast packets.
79 IFF_MASTER Master of a load balancing bundle.
80 IFF_SLAVE Slave of a load balancing bundle.
81 IFF_MULTICAST Supports multicast
82 IFF_PORTSEL Is able to select media type via ifmap.
83 IFF_AUTOMEDIA Auto media selection active.
84 IFF_DYNAMIC The addresses are lost when the interface goes
85 down.
86 IFF_LOWER_UP Driver signals L1 up (since Linux 2.6.17)
87 IFF_DORMANT Driver signals dormant (since Linux 2.6.17)
88 IFF_ECHO Echo sent packets (since Linux 2.6.25)
89 Setting the active flag word is a privileged operation, but any
92 process may read it.
93 SIOCGIFMETRIC, SIOCSIFMETRIC
95 Get or set the metric of the device using ifr_metric. This is
96 currently not implemented; it sets ifr_metric to 0 if you
97 attempt to read it and returns EOPNOTSUPP if you attempt to set
98 it.
99 SIOCGIFMTU, SIOCSIFMTU
101 Get or set the MTU (Maximum Transfer Unit) of a device using
102 ifr_mtu. Setting the MTU is a privileged operation. Setting
103 the MTU to too small values may cause kernel crashes.
104 SIOCGIFHWADDR, SIOCSIFHWADDR
106 Get or set the hardware address of a device using ifr_hwaddr.
107 The hardware address is specified in a struct sockaddr. sa_fam‐
108 ily contains the ARPHRD_* device type, sa_data the L2 hardware
109 address starting from byte 0. Setting the hardware address is a
110 privileged operation.
111 SIOCSIFHWBROADCAST
113 Set the hardware broadcast address of a device from ifr_hwaddr.
114 This is a privileged operation.
115 SIOCGIFMAP, SIOCSIFMAP
117 Get or set the interface's hardware parameters using ifr_map.
118 Setting the parameters is a privileged operation.
119 struct ifmap {
121 unsigned long mem_start;
122 unsigned long mem_end;
123 unsigned short base_addr;
124 unsigned char irq;
125 unsigned char dma;
126 unsigned char port;
127 };
128 The interpretation of the ifmap structure depends on the device
130 driver and the architecture.
131 SIOCADDMULTI, SIOCDELMULTI
133 Add an address to or delete an address from the device's link
134 layer multicast filters using ifr_hwaddr. These are privileged
135 operations. See also packet(7) for an alternative.
136 SIOCGIFTXQLEN, SIOCSIFTXQLEN
138 Get or set the transmit queue length of a device using ifr_qlen.
139 Setting the transmit queue length is a privileged operation.
140 SIOCSIFNAME
142 Changes the name of the interface specified in ifr_name to
143 ifr_newname. This is a privileged operation. It is only
144 allowed when the interface is not up.
145 SIOCGIFCONF
147 Return a list of interface (transport layer) addresses. This
148 currently means only addresses of the AF_INET (IPv4) family for
149 compatibility. The user passes a ifconf structure as argument
150 to the ioctl. It contains a pointer to an array of ifreq struc‐
151 tures in ifc_req and its length in bytes in ifc_len. The kernel
152 fills the ifreqs with all current L3 interface addresses that
153 are running: ifr_name contains the interface name (eth0:1 etc.),
154 ifr_addr the address. The kernel returns with the actual length
155 in ifc_len. If ifc_len is equal to the original length the buf‐
156 fer probably has overflowed and you should retry with a bigger
157 buffer to get all addresses. When no error occurs the ioctl
158 returns 0; otherwise -1. Overflow is not an error.
159 Most protocols support their own ioctls to configure protocol-specific
161 interface options. See the protocol man pages for a description. For
162 configuring IP addresses see ip(7).
163 In addition some devices support private ioctls. These are not
165 described here.
166
168 Strictly speaking, SIOCGIFCONF is IP specific and belongs in ip(7).
169 The names of interfaces with no addresses or that don't have the
171 IFF_RUNNING flag set can be found via /proc/net/dev.
172 Local IPv6 IP addresses can be found via /proc/net or via rtnetlink(7).
174
176 glibc 2.1 is missing the ifr_newname macro in <net/if.h>. Add the fol‐
177 lowing to your program as a workaround:
178 #ifndef ifr_newname
180 #define ifr_newname ifr_ifru.ifru_slave
181 #endif
182
184 proc(5), capabilities(7), ip(7), rtnetlink(7)
185
187 This page is part of release 3.25 of the Linux man-pages project. A
188 description of the project, and information about reporting bugs, can
189 be found at http://www.kernel.org/doc/man-pages/.
190Linux 2009-01-14 NETDEVICE(7)