xref: /dragonfly/lib/libc/net/getifaddrs.3 (revision cfd1aba3) 
1.\"	$KAME: getifaddrs.3,v 1.4 2000/05/17 14:13:14 itojun Exp $
2.\"	BSDI	getifaddrs.3,v 2.5 2000/02/23 14:51:59 dab Exp
3.\"
4.\" Copyright (c) 1995, 1999
5.\"	Berkeley Software Design, Inc.  All rights reserved.
6.\"
7.\" Redistribution and use in source and binary forms, with or without
8.\" modification, are permitted provided that the following conditions
9.\" are met:
10.\" 1. Redistributions of source code must retain the above copyright
11.\"    notice, this list of conditions and the following disclaimer.
12.\"
13.\" THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16.\" ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23.\" SUCH DAMAGE.
24.\"
25.\" $FreeBSD: src/lib/libc/net/getifaddrs.3,v 1.10 2005/02/09 18:03:13 ru Exp $
26.\"
27.Dd February 24, 2014
28.Dt GETIFADDRS 3
29.Os
30.Sh NAME
31.Nm getifaddrs
32.Nd get interface addresses
33.Sh LIBRARY
34.Lb libc
35.Sh SYNOPSIS
36.In sys/types.h
37.In sys/socket.h
38.In ifaddrs.h
39.Ft int
40.Fn getifaddrs "struct ifaddrs **ifap"
41.Ft void
42.Fn freeifaddrs "struct ifaddrs *ifp"
43.Sh DESCRIPTION
44The
45.Fn getifaddrs
46function stores a reference to a linked list of the network interfaces
47on the local machine in the memory referenced by
48.Fa ifap .
49The list consists of
50.Nm ifaddrs
51structures, as defined in the include file
52.In ifaddrs.h .
53The
54.Nm ifaddrs
55structure contains at least the following entries:
56.Bd -literal
57    struct ifaddrs   *ifa_next;         /* Pointer to next struct */
58    char             *ifa_name;         /* Interface name */
59    u_int             ifa_flags;        /* Interface flags */
60    struct sockaddr  *ifa_addr;         /* Interface address */
61    struct sockaddr  *ifa_netmask;      /* Interface netmask */
62    struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
63    void             *ifa_data;         /* Address specific data */
64.Ed
65.Pp
66The
67.Fa ifa_next
68field contains a pointer to the next structure on the list.
69This field is
70.Dv NULL
71in last structure on the list.
72.Pp
73The
74.Fa ifa_name
75field contains the interface name.
76.Pp
77The
78.Fa ifa_flags
79field contains the interface flags, as set by
80.Xr ifconfig 8
81utility.
82.Pp
83The
84.Fa ifa_addr
85field references either the address of the interface or the link level
86address of the interface, if one exists, otherwise it is NULL.
87(The
88.Fa sa_family
89field of the
90.Fa ifa_addr
91field should be consulted to determine the format of the
92.Fa ifa_addr
93address.)
94.Pp
95The
96.Fa ifa_netmask
97field references the netmask associated with
98.Fa ifa_addr ,
99if one is set, otherwise it is NULL.
100.Pp
101The
102.Fa ifa_dstaddr
103field references the destination address on a P2P interface,
104if one exists, otherwise it is NULL.
105.Pp
106The
107.Fa ifa_broadaddr
108field,
109which should only be referenced for non-P2P interfaces,
110references the broadcast address associated with
111.Fa ifa_addr ,
112if one exists, otherwise it is NULL.
113It is really just another name for
114.Fa ifa_dstaddr .
115.Pp
116The
117.Fa ifa_data
118field references address family specific data.
119For
120.Dv AF_LINK
121addresses it contains a pointer to the
122.Vt struct if_data
123(as defined in include file
124.In net/if.h )
125which contains various interface attributes and statistics.
126For all other address families, it contains a pointer to the
127.Vt struct ifa_data
128(as defined in include file
129.In net/if.h )
130which contains per-address interface statistics.
131.Pp
132The data returned by
133.Fn getifaddrs
134is dynamically allocated and should be freed using
135.Fn freeifaddrs
136when no longer needed.
137.Sh RETURN VALUES
138.Rv -std getifaddrs
139.Sh ERRORS
140The
141.Fn getifaddrs
142may fail and set
143.Va errno
144for any of the errors specified for the library routines
145.Xr ioctl 2 ,
146.Xr socket 2 ,
147.Xr malloc 3
148or
149.Xr sysctl 3 .
150.Sh SEE ALSO
151.Xr ioctl 2 ,
152.Xr socket 2 ,
153.Xr sysctl 3 ,
154.Xr networking 4 ,
155.Xr ifconfig 8
156.Sh HISTORY
157The
158.Nm
159implementation first appeared in BSDi
160.Bsx .
161.Sh BUGS
162If both
163.In net/if.h
164and
165.In ifaddrs.h
166are being included,
167.In net/if.h
168.Em must
169be included before
170.In ifaddrs.h .
171