1 /* ifaddrs.h -- declarations for getting network interface addresses 2 Copyright (C) 2002-2022 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 */ 74