1.\" $OpenBSD: getifaddrs.3,v 1.23 2022/03/29 18:15:52 naddy Exp $ 2.\" BSDI getifaddrs.3,v 2.5 2000/02/23 14:51:59 dab Exp 3.\" 4.\" Copyright (c) 1995, 1999 5.\" Berkeley Software Design, Inc. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.Dd $Mdocdate: March 29 2022 $ 25.Dt GETIFADDRS 3 26.Os 27.Sh NAME 28.Nm getifaddrs , 29.Nm freeifaddrs 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 *ifap" 39.Sh DESCRIPTION 40The 41.Fn getifaddrs 42function stores a reference to a linked list of the network interfaces 43on the local machine in the memory referenced by 44.Fa ifap . 45The list consists of 46.Vt ifaddrs 47structures, as defined in the include file 48.In ifaddrs.h . 49The 50.Vt ifaddrs 51structure 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.Bl -tag -width ifa_broadaddr 63.It Fa ifa_next 64Contains a pointer to the next structure on the list. 65This field is set to 66.Dv NULL 67in the last structure on the list. 68.It Fa ifa_name 69Contains the interface name. 70.It Fa ifa_flags 71Contains the interface flags, as set by 72.Xr ifconfig 8 . 73.It Fa ifa_addr 74References either the address of the interface or the link level 75address of the interface, if one exists, otherwise it is 76.Dv NULL . 77(The 78.Fa sa_family 79field of the 80.Fa ifa_addr 81field should be consulted to determine the format of the 82.Fa ifa_addr 83address.) 84.It Fa ifa_netmask 85References the netmask associated with 86.Fa ifa_addr , 87if one is set, otherwise it is 88.Dv NULL . 89.It Fa ifa_broadaddr 90This field, which should only be referenced for non-P2P interfaces, 91references the broadcast address associated with 92.Fa ifa_addr , 93if one exists, otherwise it is 94.Dv NULL . 95.It Fa ifa_dstaddr 96This field, which should only be referenced for P2P interfaces, 97references the destination address on a P2P interface, 98if one exists, otherwise it is 99.Dv NULL . 100.It Fa ifa_data 101References address family specific data. 102For 103.Dv AF_LINK 104addresses it contains a pointer to the 105.Vt struct if_data 106(as defined in include file 107.In net/if.h ) 108which contains various interface attributes and statistics. 109For all other address families, 110.Fa ifa_data 111is 112.Dv NULL . 113.El 114.Pp 115The data returned by 116.Fn getifaddrs 117is dynamically allocated and should be freed using 118.Fn freeifaddrs 119when no longer needed. 120.Sh RETURN VALUES 121.Rv -std 122.Sh ERRORS 123The 124.Fn getifaddrs 125function may fail and set 126.Va errno 127for any of the errors specified for the library routines 128.Xr ioctl 2 , 129.Xr socket 2 , 130.Xr malloc 3 , 131or 132.Xr sysctl 2 . 133.Sh SEE ALSO 134.Xr ioctl 2 , 135.Xr socket 2 , 136.Xr sysctl 2 , 137.Xr netintro 4 , 138.Xr ifconfig 8 139.Sh HISTORY 140The 141.Fn getifaddrs 142function first appeared in BSDI 143.Bsx . 144The function has been available on 145.Ox 146since 147.Ox 2.7 . 148.Sh BUGS 149If both 150.In net/if.h 151and 152.In ifaddrs.h 153are being included, 154.In net/if.h 155.Em must 156be included before 157.In ifaddrs.h . 158