'\" t
-.\" Don't change the first line, it tells man that tbl is needed.
.\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>.
+.\"
+.\" %%%LICENSE_START(VERBATIM_ONE_PARA)
.\" Permission is granted to distribute possibly modified copies
.\" of this page provided the header is included verbatim,
.\" and in case of nontrivial modification author and date
.\" of the modification is added to the header.
+.\" %%%LICENSE_END
+.\"
.\" $Id: netdevice.7,v 1.10 2000/08/17 10:09:54 ak Exp $
.\"
.\" Modified, 2004-11-25, mtk, formatting and a few wording fixes
.\" Modified, 2011-11-02, <bidulock@openss7.org>, added many basic
.\" but missing ioctls, such as SIOCGIFADDR.
.\"
-.TH NETDEVICE 7 2012-04-26 "Linux" "Linux Programmer's Manual"
+.TH NETDEVICE 7 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
netdevice \- low-level access to Linux network devices
.SH SYNOPSIS
.SH DESCRIPTION
This man page describes the sockets interface which is used to configure
network devices.
-
+.PP
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
+Most of them pass an
.I ifreq
structure:
-
+.PP
.in +4n
-.nf
+.EX
struct ifreq {
char ifr_name[IFNAMSIZ]; /* Interface name */
union {
char *ifr_data;
};
};
-
-struct ifconf {
- int ifc_len; /* size of buffer */
- union {
- char *ifc_buf; /* buffer address */
- struct ifreq *ifc_req; /* array of structures */
- };
-};
-.fi
+.EE
.in
-
+.PP
Normally, the user specifies which device to affect by setting
.I ifr_name
to the name of the interface.
All other members of the structure may
share memory.
.SS Ioctls
-If an ioctl is marked as privileged then using it requires an effective
+If an ioctl is marked as privileged, then using it requires an effective
user ID of 0 or the
.B CAP_NET_ADMIN
capability.
-If this is not the case
+If this is not the case,
.B EPERM
will be returned.
.TP
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)
-
-
.TE
.ad
+.PP
Setting the active flag word is a privileged operation, but any
process may read it.
.TP
IFF_SLAVE_NEEDARP:Interface needs ARPs for validation.
IFF_ISATAP:Interface is RFC4214 ISATAP interface.
.TE
-.sp
+.PP
Setting the extended (private) interface flags is a privileged operation.
.TP
.BR SIOCGIFADDR ", " SIOCSIFADDR
Get or set the interface's hardware parameters using
.IR ifr_map .
Setting the parameters is a privileged operation.
-
+.IP
.in +4n
-.nf
+.EX
struct ifmap {
unsigned long mem_start;
unsigned long mem_end;
unsigned char dma;
unsigned char port;
};
-.fi
+.EE
.in
-
+.IP
The interpretation of the ifmap structure depends on the device driver
and the architecture.
.TP
to
.IR ifr_newname .
This is a privileged operation.
-It is only allowed when the interface
+It is allowed only when the interface
is not up.
.TP
.B SIOCGIFCONF
means only addresses of the
.B AF_INET
(IPv4) family for compatibility.
-The user passes a
+Unlike the others, this ioctl passes an
.I ifconf
-structure as argument to the ioctl.
-It contains a pointer to an array of
-.I ifreq
-structures in
+structure:
+.IP
+.in +4n
+.EX
+struct ifconf {
+ int ifc_len; /* size of buffer */
+ union {
+ char *ifc_buf; /* buffer address */
+ struct ifreq *ifc_req; /* array of structures */
+ };
+};
+.EE
+.in
+.IP
+If
.I ifc_req
-and its length in bytes in
+is NULL,
+.B SIOCGIFCONF
+returns the necessary buffer size in bytes
+for receiving all available addresses in
.IR ifc_len .
-The kernel fills the ifreqs with all current L3 interface addresses that
-are running:
+Otherwise,
+.I ifc_req
+contains a pointer to an array of
+.I ifreq
+structures to be filled with all currently active L3 interface addresses.
+.I ifc_len
+contains the size of the array in bytes.
+Within each
+.I ifreq
+structure,
.I ifr_name
-contains the interface name (eth0:1 etc.),
+will receive the interface name, and
.I ifr_addr
the address.
-The kernel returns with the actual length in
+The actual number of bytes transferred is returned in
.IR ifc_len .
-If
+.IP
+If the size specified by
.I ifc_len
-is equal to the original length the buffer probably has overflowed
-and you should retry with a bigger buffer to get all addresses.
-When no error occurs the ioctl returns 0;
-otherwise \-1.
-Overflow is not an error.
+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
+.B SIOCGIFCONF
+with
+.I ifc_req
+set to NULL, or to retry the call with a bigger buffer whenever
+.I ifc_len
+upon return differs by less than
+.I sizeof(struct ifreq)
+from its original value.
+.IP
+If an error occurs accessing the
+.I ifconf
+or
+.I ifreq
+structures,
+.B EFAULT
+will be returned.
.\" Slaving isn't supported in 2.2
.\" .
.\" .TP
.\" .IR ifr_slave .
.\" Setting the slave device is a privileged operation.
.\" .PP
-.\" FIXME add amateur radio stuff.
+.\" FIXME . add amateur radio stuff.
.PP
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
+For configuring IP addresses, see
.BR ip (7).
.PP
-In addition some devices support private ioctls.
+In addition, some devices support private ioctls.
These are not described here.
.SH NOTES
Strictly speaking,
.B SIOCGIFCONF
-and the other ioctls that only accept or return
+and the other ioctls that accept or return only
.B AF_INET
socket addresses,
-are IP specific and belong in
+are IP-specific and belong in
.BR ip (7).
-.LP
+.PP
The names of interfaces with no addresses or that don't have the
.B IFF_RUNNING
flag set can be found via
.IR /proc/net/dev .
-.LP
+.PP
Local IPv6 IP addresses can be found via
.I /proc/net
or via
macro in
.IR <net/if.h> .
Add the following to your program as a workaround:
-.sp
+.PP
.in +4n
-.nf
+.EX
#ifndef ifr_newname
#define ifr_newname ifr_ifru.ifru_slave
#endif
-.fi
+.EE
.in
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR proc (5),
.BR capabilities (7),
.BR ip (7),
projects / thirdparty / man-pages.git / blobdiff