NAME
getifaddrs
—
get interface addresses
SYNOPSIS
#include
<sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
int
getifaddrs
(struct
ifaddrs **ifap);
void
freeifaddrs
(struct
ifaddrs *ifap);
DESCRIPTION
The
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 */ 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 */
- ifa_next
- Contains a pointer to the next structure on the list. This field is set to
NULL
in the last structure on the list. - ifa_name
- Contains the interface name.
- ifa_flags
- Contains the interface flags, as set by ifconfig(8).
- ifa_addr
- 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.) - ifa_netmask
- References the netmask associated with ifa_addr, if
one is set, otherwise it is
NULL
. - ifa_broadaddr
- This 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
. - ifa_dstaddr
- This field, which should only be referenced for P2P interfaces, references
the destination address on a P2P interface, if one exists, otherwise it is
NULL
. - ifa_data
- References address family specific data. For
AF_LINK
addresses it contains a pointer to thestruct if_data
(as defined in include file ⟨net/if.h⟩) which contains various interface attributes and statistics. For all other address families, ifa_data isNULL
.
The data returned by
getifaddrs
()
is dynamically allocated and should be freed using
freeifaddrs
()
when no longer needed.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.
ERRORS
The 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).
SEE ALSO
HISTORY
The getifaddrs
() function first appeared
in BSDI BSD/OS. The function has been available on
OpenBSD since OpenBSD
2.7.
BUGS
If both ⟨net/if.h⟩ and ⟨ifaddrs.h⟩ are being included, ⟨net/if.h⟩ must be included before ⟨ifaddrs.h⟩.