man7/netdevice.7

   1 '\" t
   2 .\" Don't change the first line, it tells man that tbl is needed.
   3 .\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>.
   4 .\" Permission is granted to distribute possibly modified copies
   5 .\" of this page provided the header is included verbatim,
   6 .\" and in case of nontrivial modification author and date
   7 .\" of the modification is added to the header.
   8 .\" $Id: netdevice.7,v 1.10 2000/08/17 10:09:54 ak Exp $
   9 .\"
  10 .\" Modified, 2004-11-25, mtk, formatting and a few wording fixes
  11 .\"
  12 .TH NETDEVICE  7 1999-05-02 "Linux Man Page" "Linux Programmer's Manual"
  13 .SH NAME
  14 netdevice \- Low level access to Linux network devices
  15 .SH SYNOPSIS
  16 .B "#include <sys/ioctl.h>"
  17 .br
  18 .B "#include <net/if.h>"
  19 .SH DESCRIPTION
  20 This man page describes the sockets interface which is used to configure
  21 network devices.
  22
  23 Linux supports some standard ioctls to configure network devices.
  24 They can be used on any socket's file descriptor regardless of the
  25 family or type.
  26 They pass an
  27 .B ifreq
  28 structure:
  29
  30 .nf
  31 struct ifreq {
  32     char ifr_name[IFNAMSIZ]; /* Interface name */
  33     union {
  34         struct sockaddr ifr_addr;
  35         struct sockaddr ifr_dstaddr;
  36         struct sockaddr ifr_broadaddr;
  37         struct sockaddr ifr_netmask;
  38         struct sockaddr ifr_hwaddr;
  39         short           ifr_flags;
  40         int             ifr_ifindex;
  41         int             ifr_metric;
  42         int             ifr_mtu;
  43         struct ifmap    ifr_map;
  44         char            ifr_slave[IFNAMSIZ];
  45         char            ifr_newname[IFNAMSIZ];
  46         char *          ifr_data;
  47     };
  48 };
  49
  50 struct ifconf {
  51     int                ifc_len; /* size of buffer */
  52     union {
  53         char *         ifc_buf; /* buffer address */
  54         struct ifreq * ifc_req; /* array of structures */
  55     };
  56 };
  57 .fi
  58
  59 Normally, the user specifies which device to affect by setting
  60 .B ifr_name
  61 to the name of the interface.
  62 All other members of the structure may
  63 share memory.
  64 .SH IOCTLS
  65 If an ioctl is marked as privileged then using it requires an effective
  66 user ID of 0 or the
  67 .B CAP_NET_ADMIN
  68 capability.
  69 If this is not the case
  70 .B EPERM
  71 will be returned.
  72 .TP
  73 .B SIOCGIFNAME
  74 Given the
  75 .BR ifr_ifindex ,
  76 return the name of the interface in
  77 .BR ifr_name .
  78 This is the only ioctl which returns its result in
  79 .BR ifr_name .
  80 .TP
  81 .B SIOCGIFINDEX
  82 Retrieve the interface index of the interface into
  83 .BR ifr_ifindex .
  84 .TP
  85 .BR SIOCGIFFLAGS ", " SIOCSIFFLAGS
  86 Get or set the active flag word of the device.
  87 .B ifr_flags
  88 contains a bitmask of the following values:
  89 .TS
  90 tab(:);
  91 c s
  92 l l.
  93 Device flags
  94 IFF_UP:Interface is running.
  95 IFF_BROADCAST:Valid broadcast address set.
  96 IFF_DEBUG:Internal debugging flag.
  97 IFF_LOOPBACK:Interface is a loopback interface.
  98 IFF_POINTOPOINT:Interface is a point-to-point link.
  99 IFF_RUNNING:Resources allocated.
 100 IFF_NOARP:No arp protocol, L2 destination address not set.
 101 IFF_PROMISC:Interface is in promiscuous mode.
 102 IFF_NOTRAILERS:Avoid use of trailers.
 103 IFF_ALLMULTI:Receive all multicast packets.
 104 IFF_MASTER:Master of a load balancing bundle.
 105 IFF_SLAVE:Slave of a load balancing bundle.
 106 IFF_MULTICAST:Supports multicast
 107 IFF_PORTSEL:Is able to select media type via ifmap.
 108 IFF_AUTOMEDIA:Auto media selection active.
 109 IFF_DYNAMIC:T{
 110 The addresses are lost when the interface goes down.
 111 T}
 112 .TE
 113 Setting the active flag word is a privileged operation, but any
 114 process may read it.
 115 .TP
 116 .BR SIOCGIFMETRIC ", " SIOCSIFMETRIC
 117 Get or set the metric of the device using
 118 .BR ifr_metric .
 119 This is currently not implemented; it sets
 120 .B ifr_metric
 121 to 0 if you attempt to read it and returns
 122 .B EOPNOTSUPP
 123 if you attempt to set it.
 124 .TP
 125 .BR SIOCGIFMTU ", " SIOCSIFMTU
 126 Get or set the MTU (Maximum Transfer Unit) of a device using
 127 .BR ifr_mtu .
 128 Setting the MTU is a privileged operation.
 129 Setting the MTU to
 130 too small values may cause kernel crashes.
 131 .TP
 132 .BR SIOCGIFHWADDR ", " SIOCSIFHWADDR
 133 Get or set the hardware address of a device using
 134 .BR ifr_hwaddr .
 135 The hardware address is specified in a struct
 136 .IR sockaddr .
 137 .I sa_family
 138 contains the ARPHRD_* device type,
 139 .I sa_data
 140 the L2 hardware address starting from byte 0.
 141 Setting the hardware address is a privileged operation.
 142 .TP
 143 .B SIOCSIFHWBROADCAST
 144 Set the hardware broadcast address of a device from
 145 .BR ifr_hwaddr .
 146 This is a privileged operation.
 147 .TP
 148 .BR SIOCGIFMAP ", " SIOCSIFMAP
 149 Get or set the interface's hardware parameters using
 150 .BR ifr_map .
 151 Setting the parameters is a privileged operation.
 152
 153 .nf
 154 struct ifmap {
 155     unsigned long   mem_start;
 156     unsigned long   mem_end;
 157     unsigned short  base_addr;
 158     unsigned char   irq;
 159     unsigned char   dma;
 160     unsigned char   port;
 161 };
 162 .fi
 163
 164 The interpretation of the ifmap structure depends on the device driver
 165 and the architecture.
 166 .TP
 167 .BR SIOCADDMULTI ", " SIOCDELMULTI
 168 Add an address to or delete an address from the device's link layer
 169 multicast filters using
 170 .BR ifr_hwaddr .
 171 These are privileged operations.
 172 See also
 173 .BR packet (7)
 174 for an alternative.
 175 .TP
 176 .BR SIOCGIFTXQLEN ", " SIOCSIFTXQLEN
 177 Get or set the transmit queue length of a device using
 178 .BR ifr_qlen .
 179 Setting the transmit queue length is a privileged operation.
 180 .TP
 181 .B SIOCSIFNAME
 182 Changes the name of the interface specified in
 183 .BR ifr_name
 184 to
 185 .BR ifr_newname .
 186 This is a privileged operation.
 187 It is only allowed when the interface
 188 is not up.
 189 .TP
 190 .B SIOCGIFCONF
 191 Return a list of interface (transport layer) addresses.
 192 This currently
 193 means only addresses of the AF_INET (IPv4) family for compatibility.
 194 The user passes a
 195 .B ifconf
 196 structure as argument to the ioctl.
 197 It contains a pointer to an array of
 198 .I ifreq
 199 structures in
 200 .B ifc_req
 201 and its length in bytes in
 202 .BR ifc_len .
 203 The kernel fills the ifreqs with all current L3 interface addresses that
 204 are running:
 205 .I ifr_name
 206 contains the interface name (eth0:1 etc.),
 207 .I ifr_addr
 208 the address.
 209 The kernel returns with the actual length in
 210 .IR ifc_len .
 211 If
 212 .I ifc_len
 213 is equal to the original length the buffer probably has overflowed
 214 and you should retry with a bigger buffer to get all addresses.
 215 When no error occurs the ioctl returns 0;
 216 otherwise \-1.
 217 Overflow is not an error.
 218 .\" FIXME Slaving isn't supported in 2.2
 219 .\" .
 220 .\" .TP
 221 .\" .BR SIOCGIFSLAVE ", " SIOCSIFSLAVE
 222 .\" Get or set the slave device using
 223 .\" .BR ifr_slave .
 224 .\" Setting the slave device is a privileged operation.
 225 .\" .PP
 226 .\" FIXME add amateur radio stuff.
 227 .PP
 228 Most protocols support their own ioctls to configure protocol specific
 229 interface options.
 230 See the protocol man pages for a description.
 231 For configuring IP addresses see
 232 .BR ip (7).
 233 .PP
 234 In addition some devices support private ioctls.
 235 These are not described here.
 236 .SH NOTES
 237 Strictly speaking,
 238 .B SIOCGIFCONF
 239 is IP specific and belongs in
 240 .BR ip (7).
 241 .LP
 242 The names of interfaces with no addresses or that don't have the
 243 .B IFF_RUNNING
 244 flag set can be found via
 245 .IR /proc/net/dev .
 246 .LP
 247 Local IPv6 IP addresses can be found via /proc/net or via
 248 .BR rtnetlink (7).
 249 .SH BUGS
 250 glibc 2.1 is missing the
 251 .I ifr_newname
 252 macro in net/if.h.
 253 Add the following to your program as a workaround:
 254 .sp
 255 .RS
 256 .nf
 257 #ifndef ifr_newname
 258 #define ifr_newname     ifr_ifru.ifru_slave
 259 #endif
 260 .fi
 261 .RE
 262 .SH "SEE ALSO"
 263 .BR capabilities (7),
 264 .BR ip (7),
 265 .BR proc (7),
 266 .BR rtnetlink (7)