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.\"     $OpenBSD: getifaddrs.3,v 1.7 2001/10/01 21:58:53 millert Exp $

.\"     BSDI    getifaddrs.3,v 2.5 2000/02/23 14:51:59 dab Exp

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.Dd "October 12, 1995"

.Dt GETIFADDRS 3

.Sh NAME

.Nm getifaddrs

.Nd get interface addresses

.Sh SYNOPSIS

.Fd #include 

.Fd #include 

.Fd #include 

.Ft int

.Fn getifaddrs "struct ifaddrs **ifap"

.Ft void

.Fn freeifaddrs "struct ifaddrs *ifap"

.Sh DESCRIPTION

The

.Fn getifaddrs

function stores a reference to a linked list of the network interfaces

on the local machine in the memory referenced by

.Fa ifap .

The list consists of

.Nm ifaddrs

structures, as defined in the include file

.Aq Pa ifaddrs.h .

The

.Nm ifaddrs

structure contains at least the following entries:

.Bd -literal

    struct ifaddrs   *ifa_next;         /* Pointer to next struct */

    char             *ifa_name;         /* Interface name */

    u_int             ifa_flags;        /* Interface flags */

    struct sockaddr  *ifa_addr;         /* Interface address */

    struct sockaddr  *ifa_netmask;      /* Interface netmask */

    struct sockaddr  *ifa_broadaddr;    /* Interface broadcast address */

    struct sockaddr  *ifa_dstaddr;      /* P2P interface destination */

    void             *ifa_data;         /* Address specific data */

.Ed

.Pp

.Bl -tag -width Ds

.It Fa ifa_next

Contains a pointer to the next structure on the list.

This field is set to

.Dv NULL

in last structure on the list.

.It Fa ifa_name

Contains the interface name.

.It Fa ifa_flags

Contains the interface flags, as set by

.Xr ifconfig 8 .

.It Fa ifa_addr

References either the address of the interface or the link level

address of the interface, if one exists, otherwise it is

.Dv NULL .

(The

.Fa sa_family

field of the

.Fa ifa_addr

field should be consulted to determine the format of the

.Fa ifa_addr

address.)

.It Fa ifa_netmask

References the netmask associated with

.Fa ifa_addr ,

if one is set, otherwise it is

.Dv NULL .

.It Fa ifa_broadaddr

This field, which should only be referenced for non-P2P interfaces,

references the broadcast address associated with

.Fa ifa_addr ,

if one exists, otherwise it is

.Dv NULL .

.It Fa ifa_dstaddr

References the destination address on a P2P interface,

if one exists, otherwise it is

.Dv NULL .

.It Fa ifa_data

References address family specific data.

For

.Dv AF_LINK

addresses it contains a pointer to the

.Li struct if_data

(as defined in include file

.Aq Pa net/if.h )

which contains various interface attributes and statistics.

For all other address families, it contains a pointer to the

.Li struct ifa_data

(as defined in include file

.Aq Pa net/if.h )

which contains per-address interface statistics.

.El

.Pp

The data returned by

.Fn getifaddrs

is dynamically allocated and should be freed using

.Fn freeifaddrs

when no longer needed.

.Sh RETURN VALUES

Upon successful completion, a value of 0 is returned.

Otherwise, a value of \-1 is returned and

.Va errno

is set to indicate the error.

.Sh ERRORS

The

.Fn getifaddrs

may fail and set

.Va errno

for any of the errors specified for the library routines

.Xr ioctl 2 ,

.Xr socket 2 ,

.Xr malloc 3 ,

or

.Xr sysctl 3 .

.Sh BUGS

If both

.Aq Pa net/if.h

and

.Aq Pa ifaddrs.h

are being included,

.Aq Pa net/if.h

.Em must

be included before

.Aq Pa ifaddrs.h .

.Sh SEE ALSO

.Xr ioctl 2 ,

.Xr socket 2 ,

.Xr sysctl 3 ,

.Xr networking 4 ,

.Xr ifconfig 8

.Sh HISTORY

The

.Fn getifaddrs

function first appeared in BSDI BSD/OS.

The function is supplied on

.Ox

since

.Ox 2.7 .