net/getifaddrs.3

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   2 .\"     $KAME: getifaddrs.3,v 1.4 2000/05/17 14:13:14 itojun Exp $
   3 .\"     BSDI    getifaddrs.3,v 2.5 2000/02/23 14:51:59 dab Exp
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  25 .Dd October 12, 1995
  26 .Dt GETIFADDRS 3
  27 .Os
  28 .Sh NAME
  29 .Nm getifaddrs
  30 .Nd get interface addresses
  31 .Sh SYNOPSIS
  32 .In sys/types.h
  33 .In sys/socket.h
  34 .In ifaddrs.h
  35 .Ft int
  36 .Fn getifaddrs "struct ifaddrs **ifap"
  37 .Ft void
  38 .Fn freeifaddrs "struct ifaddrs *ifp"
  39 .Sh DESCRIPTION
  40 The
  41 .Fn getifaddrs
  42 function stores a reference to a linked list of the network interfaces
  43 on the local machine in the memory referenced by
  44 .Fa ifap .
  45 The list consists of
  46 .Nm ifaddrs
  47 structures, as defined in the include file
  48 .Aq Pa ifaddrs.h .
  49 The
  50 .Nm ifaddrs
  51 structure contains at least the following entries:
  52 .Bd -literal
  53     struct ifaddrs   *ifa_next;         /* Pointer to next struct */
  54     char             *ifa_name;         /* Interface name */
  55     u_int             ifa_flags;        /* Interface flags */
  56     struct sockaddr  *ifa_addr;         /* Interface address */
  57     struct sockaddr  *ifa_netmask;      /* Interface netmask */
  58     struct sockaddr  *ifa_broadaddr;    /* Interface broadcast address */
  59     struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */
  60     void             *ifa_data;         /* Address specific data */
  61 .Ed
  62 .Pp
  63 The
  64 .Li ifa_next
  65 field contains a pointer to the next structure on the list.
  66 This field is
  67 .Dv NULL
  68 in last structure on the list.
  69 .Pp
  70 The
  71 .Li ifa_name
  72 field contains the interface name.
  73 .Pp
  74 The
  75 .Li ifa_flags
  76 field contains the interface flags, as set by
  77 .Xr ifconfig 8
  78 utility.
  79 .Pp
  80 The
  81 .Li ifa_addr
  82 field references either the address of the interface or the link level
  83 address of the interface, if one exists, otherwise it is NULL.
  84 (The
  85 .Li sa_family
  86 field of the
  87 .Li ifa_addr
  88 field should be consulted to determine the format of the
  89 .Li ifa_addr
  90 address.)
  91 .Pp
  92 The
  93 .Li ifa_netmask
  94 field references the netmask associated with
  95 .Li ifa_addr ,
  96 if one is set, otherwise it is NULL.
  97 .Pp
  98 The
  99 .Li ifa_broadaddr
 100 field,
 101 which should only be referenced for non-P2P interfaces,
 102 references the broadcast address associated with
 103 .Li ifa_addr ,
 104 if one exists, otherwise it is NULL.
 105 .Pp
 106 The
 107 .Li ifa_dstaddr
 108 field references the destination address on a P2P interface,
 109 if one exists, otherwise it is NULL.
 110 .Pp
 111 The
 112 .Li ifa_data
 113 field references address family specific data.  For
 114 .Dv AF_LINK
 115 addresses it contains a pointer to the
 116 .Fa struct if_data
 117 (as defined in include file
 118 .Aq Pa net/if.h )
 119 which contains various interface attributes and statistics.
 120 For all other address families, it contains a pointer to the
 121 .Fa struct ifa_data
 122 (as defined in include file
 123 .Aq Pa net/if.h )
 124 which contains per-address interface statistics.
 125 .Pp
 126 The data returned by
 127 .Fn getifaddrs
 128 is dynamically allocated and should be freed using
 129 .Fn freeifaddrs
 130 when no longer needed.
 131 .Sh RETURN VALUES
 132 .Rv -std getifaddrs
 133 .Sh ERRORS
 134 The
 135 .Fn getifaddrs
 136 may fail and set
 137 .Va errno
 138 for any of the errors specified for the library routines
 139 .Xr ioctl 2 ,
 140 .Xr socket 2 ,
 141 .Xr malloc 3
 142 or
 143 .Xr sysctl 3 .
 144 .Sh BUGS
 145 If both
 146 .Aq Pa net/if.h
 147 and
 148 .Aq Pa ifaddrs.h
 149 are being included,
 150 .Aq Pa net/if.h
 151 .Em must
 152 be included before
 153 .Aq Pa ifaddrs.h .
 154 .Sh SEE ALSO
 155 .Xr ioctl 2 ,
 156 .Xr socket 2 ,
 157 .Xr sysctl 3 ,
 158 .Xr networking 4 ,
 159 .Xr ifconfig 8
 160 .Sh HISTORY
 161 The
 162 .Nm
 163 implementation first appeared in BSDi
 164 .Bsx .