xref: /dragonfly/lib/libc/net/getifaddrs.3 (revision 9f7604d7) 
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25.\" $FreeBSD: src/lib/libc/net/getifaddrs.3,v 1.10 2005/02/09 18:03:13 ru Exp $
26.\" $DragonFly: src/lib/libc/net/getifaddrs.3,v 1.5 2007/08/18 20:48:47 swildner Exp $
27.\"
28.Dd October 12, 1995
29.Dt GETIFADDRS 3
30.Os
31.Sh NAME
32.Nm getifaddrs
33.Nd get interface addresses
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.In sys/types.h
38.In sys/socket.h
39.In ifaddrs.h
40.Ft int
41.Fn getifaddrs "struct ifaddrs **ifap"
42.Ft void
43.Fn freeifaddrs "struct ifaddrs *ifp"
44.Sh DESCRIPTION
45The
46.Fn getifaddrs
47function stores a reference to a linked list of the network interfaces
48on the local machine in the memory referenced by
49.Fa ifap .
50The list consists of
51.Nm ifaddrs
52structures, as defined in the include file
53.In ifaddrs.h .
54The
55.Nm ifaddrs
56structure contains at least the following entries:
57.Bd -literal
58    struct ifaddrs   *ifa_next;         /* Pointer to next struct */
59    char             *ifa_name;         /* Interface name */
60    u_int             ifa_flags;        /* Interface flags */
61    struct sockaddr  *ifa_addr;         /* Interface address */
62    struct sockaddr  *ifa_netmask;      /* Interface netmask */
63    struct sockaddr  *ifa_broadaddr;    /* Interface broadcast address */
64    struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
65    void             *ifa_data;		/* Address specific data */
66.Ed
67.Pp
68The
69.Li ifa_next
70field contains a pointer to the next structure on the list.
71This field is
72.Dv NULL
73in last structure on the list.
74.Pp
75The
76.Li ifa_name
77field contains the interface name.
78.Pp
79The
80.Li ifa_flags
81field contains the interface flags, as set by
82.Xr ifconfig 8
83utility.
84.Pp
85The
86.Li ifa_addr
87field references either the address of the interface or the link level
88address of the interface, if one exists, otherwise it is NULL.
89(The
90.Li sa_family
91field of the
92.Li ifa_addr
93field should be consulted to determine the format of the
94.Li ifa_addr
95address.)
96.Pp
97The
98.Li ifa_netmask
99field references the netmask associated with
100.Li ifa_addr ,
101if one is set, otherwise it is NULL.
102.Pp
103The
104.Li ifa_broadaddr
105field,
106which should only be referenced for non-P2P interfaces,
107references the broadcast address associated with
108.Li ifa_addr ,
109if one exists, otherwise it is NULL.
110.Pp
111The
112.Li ifa_dstaddr
113field references the destination address on a P2P interface,
114if one exists, otherwise it is NULL.
115.Pp
116The
117.Li ifa_data
118field references address family specific data.
119For
120.Dv AF_LINK
121addresses it contains a pointer to the
122.Fa 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.Fa 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