xref: /dragonfly/lib/libc/net/getifaddrs.3 (revision fcce2b94) 
1.\"	$FreeBSD: src/lib/libc/net/getifaddrs.3,v 1.1.2.5 2001/12/14 18:33:55 ru Exp $
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26.Dd October 12, 1995
27.Dt GETIFADDRS 3
28.Os
29.Sh NAME
30.Nm getifaddrs
31.Nd get interface addresses
32.Sh SYNOPSIS
33.In sys/types.h
34.In sys/socket.h
35.In ifaddrs.h
36.Ft int
37.Fn getifaddrs "struct ifaddrs **ifap"
38.Ft void
39.Fn freeifaddrs "struct ifaddrs *ifp"
40.Sh DESCRIPTION
41The
42.Fn getifaddrs
43function stores a reference to a linked list of the network interfaces
44on the local machine in the memory referenced by
45.Fa ifap .
46The list consists of
47.Nm ifaddrs
48structures, as defined in the include file
49.In ifaddrs.h .
50The
51.Nm ifaddrs
52structure contains at least the following entries:
53.Bd -literal
54    struct ifaddrs   *ifa_next;         /* Pointer to next struct */
55    char             *ifa_name;         /* Interface name */
56    u_int             ifa_flags;        /* Interface flags */
57    struct sockaddr  *ifa_addr;         /* Interface address */
58    struct sockaddr  *ifa_netmask;      /* Interface netmask */
59    struct sockaddr  *ifa_broadaddr;    /* Interface broadcast address */
60    struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
61    void             *ifa_data;		/* Address specific data */
62.Ed
63.Pp
64The
65.Li ifa_next
66field contains a pointer to the next structure on the list.
67This field is
68.Dv NULL
69in last structure on the list.
70.Pp
71The
72.Li ifa_name
73field contains the interface name.
74.Pp
75The
76.Li ifa_flags
77field contains the interface flags, as set by
78.Xr ifconfig 8
79utility.
80.Pp
81The
82.Li ifa_addr
83field references either the address of the interface or the link level
84address of the interface, if one exists, otherwise it is NULL.
85(The
86.Li sa_family
87field of the
88.Li ifa_addr
89field should be consulted to determine the format of the
90.Li ifa_addr
91address.)
92.Pp
93The
94.Li ifa_netmask
95field references the netmask associated with
96.Li ifa_addr ,
97if one is set, otherwise it is NULL.
98.Pp
99The
100.Li ifa_broadaddr
101field,
102which should only be referenced for non-P2P interfaces,
103references the broadcast address associated with
104.Li ifa_addr ,
105if one exists, otherwise it is NULL.
106.Pp
107The
108.Li ifa_dstaddr
109field references the destination address on a P2P interface,
110if one exists, otherwise it is NULL.
111.Pp
112The
113.Li ifa_data
114field references address family specific data.  For
115.Dv AF_LINK
116addresses it contains a pointer to the
117.Fa struct if_data
118(as defined in include file
119.In net/if.h )
120which contains various interface attributes and statistics.
121For all other address families, it contains a pointer to the
122.Fa struct ifa_data
123(as defined in include file
124.In net/if.h )
125which contains per-address interface statistics.
126.Pp
127The data returned by
128.Fn getifaddrs
129is dynamically allocated and should be freed using
130.Fn freeifaddrs
131when no longer needed.
132.Sh RETURN VALUES
133.Rv -std getifaddrs
134.Sh ERRORS
135The
136.Fn getifaddrs
137may fail and set
138.Va errno
139for any of the errors specified for the library routines
140.Xr ioctl 2 ,
141.Xr socket 2 ,
142.Xr malloc 3
143or
144.Xr sysctl 3 .
145.Sh SEE ALSO
146.Xr ioctl 2 ,
147.Xr socket 2 ,
148.Xr sysctl 3 ,
149.Xr networking 4 ,
150.Xr ifconfig 8
151.Sh HISTORY
152The
153.Nm
154implementation first appeared in BSDi
155.Bsx .
156.Sh BUGS
157If both
158.In net/if.h
159and
160.In ifaddrs.h
161are being included,
162.In net/if.h
163.Em must
164be included before
165.In ifaddrs.h .
166