gen.subproj/getifaddrs.3

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