GETIFADDRS(3) | Library Functions Manual | GETIFADDRS(3) |
getifaddrs
, freeifaddrs
—
#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
int
getifaddrs
(struct
ifaddrs **ifap);
void
freeifaddrs
(struct
ifaddrs *ifp);
getifaddrs
() function stores a reference to a linked
list of the network interfaces on the local machine in the memory referenced
by ifap. The list consists of
ifaddrs
structures, as defined in the include file
<ifaddrs.h>
. The
ifaddrs
structure contains at least the following
entries:
struct ifaddrs *ifa_next; /* Pointer to next struct */ char *ifa_name; /* Interface name */ unsigned 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 */ unsigned int ifa_addrflags; /* Address flags */
The ifa_next
field contains a pointer to
the next structure on the list. This field is NULL
in last structure on the list.
The ifa_name
field contains the interface
name.
The ifa_flags
field contains the interface
flags, as set by ifconfig(8)
utility.
The ifa_addr
field references either the
address of the interface or the link level address of the interface, if one
exists, otherwise it is NULL
. (The
sa_family
field of the
ifa_addr
field should be consulted to determine the
format of the ifa_addr
address.)
The ifa_netmask
field references the
netmask associated with ifa_addr
, if one is set,
otherwise it is NULL
.
The ifa_broadaddr
field, which should only
be referenced for non-P2P interfaces, references the broadcast address
associated with ifa_addr
, if one exists, otherwise
it is NULL
.
The ifa_dstaddr
field references the
destination address on a P2P interface, if one exists, otherwise it is
NULL
.
The ifa_data
field references address
family specific data. For AF_LINK
addresses it
contains a pointer to the struct if_data (as defined
in include file ⟨net/if.h⟩) which
contains various interface attributes and statistics. For all other address
families, it is NULL
.
The ifa_addrflags
field contains the
address flags, which are specific to the address family.
The data returned by getifaddrs
() is
dynamically allocated and should be freed using
freeifaddrs
() when no longer needed.
#include <sys/types.h> #include <sys/socket.h> #include <stdio.h> #include <ifaddrs.h> #include <util.h> #include <err.h> #include <stdlib.h> int main(int argc, char *argv[]) { struct ifaddrs *ifa, *a; if (getifaddrs(&ifa) == -1) err(EXIT_FAILURE, "getifaddrs"); for (a = ifa; a; a = a->ifa_next) { char buf[1024]; sockaddr_snprintf(buf, sizeof(buf), "%f %a", a->ifa_addr); printf("%s %x %s\n", a->ifa_name, a->ifa_flags, buf); } freeifaddrs(ifa); return EXIT_SUCCESS; }
getifaddrs
() may fail and set
errno for any of the errors specified for the library
routines ioctl(2),
socket(2),
malloc(3) or
sysctl(3).
getifaddrs
implementation first appeared in
BSD/OS.
ifa_addrflags
was added in
NetBSD 8.0.
<net/if.h>
and
<ifaddrs.h>
are being
included, <net/if.h>
must be included before
<ifaddrs.h>
.
September 15, 2016 | NetBSD 9.0 |