inet/ifaddrs.h

   1 /* ifaddrs.h -- declarations for getting network interface addresses
   2    Copyright (C) 2002-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _IFADDRS_H
  20 #define _IFADDRS_H      1
  21
  22 #include <features.h>
  23 #include <sys/socket.h>
  24
  25 __BEGIN_DECLS
  26
  27 /* The `getifaddrs' function generates a linked list of these structures.
  28    Each element of the list describes one network interface.  */
  29 struct ifaddrs
  30 {
  31   struct ifaddrs *ifa_next;     /* Pointer to the next structure.  */
  32
  33   char *ifa_name;               /* Name of this network interface.  */
  34   unsigned int ifa_flags;       /* Flags as from SIOCGIFFLAGS ioctl.  */
  35
  36   struct sockaddr *ifa_addr;    /* Network address of this interface.  */
  37   struct sockaddr *ifa_netmask; /* Netmask of this interface.  */
  38   union
  39   {
  40     /* At most one of the following two is valid.  If the IFF_BROADCAST
  41        bit is set in `ifa_flags', then `ifa_broadaddr' is valid.  If the
  42        IFF_POINTOPOINT bit is set, then `ifa_dstaddr' is valid.
  43        It is never the case that both these bits are set at once.  */
  44     struct sockaddr *ifu_broadaddr; /* Broadcast address of this interface. */
  45     struct sockaddr *ifu_dstaddr; /* Point-to-point destination address.  */
  46   } ifa_ifu;
  47   /* These very same macros are defined by <net/if.h> for `struct ifaddr'.
  48      So if they are defined already, the existing definitions will be fine.  */
  49 # ifndef ifa_broadaddr
  50 #  define ifa_broadaddr ifa_ifu.ifu_broadaddr
  51 # endif
  52 # ifndef ifa_dstaddr
  53 #  define ifa_dstaddr   ifa_ifu.ifu_dstaddr
  54 # endif
  55
  56   void *ifa_data;               /* Address-specific data (may be unused).  */
  57 };
  58
  59
  60 /* Create a linked list of `struct ifaddrs' structures, one for each
  61    network interface on the host machine.  If successful, store the
  62    list in *IFAP and return 0.  On errors, return -1 and set `errno'.
  63
  64    The storage returned in *IFAP is allocated dynamically and can
  65    only be properly freed by passing it to `freeifaddrs'.  */
  66 extern int getifaddrs (struct ifaddrs **__ifap) __THROW;
  67
  68 /* Reclaim the storage allocated by a previous `getifaddrs' call.  */
  69 extern void freeifaddrs (struct ifaddrs *__ifa)  __THROW;
  70
  71 __END_DECLS
  72
  73 #endif /* ifaddrs.h */