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GETIFADDRS(3) Library Functions Manual GETIFADDRS(3)

getifaddrs, freeifaddrsget interface addresses

#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>

getifaddrs(struct ifaddrs **ifap);

freeifaddrs(struct ifaddrs *ifap);

The () 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 */
Contains a pointer to the next structure on the list. This field is set to NULL in the last structure on the list.
Contains the interface name.
Contains the interface flags, as set by ifconfig(8).
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.)
References the netmask associated with ifa_addr, if one is set, otherwise it is NULL.
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.
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.
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, ifa_data is NULL.

The data returned by () is dynamically allocated and should be freed using () when no longer needed.

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

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).

ioctl(2), socket(2), sysctl(3), networking(4), ifconfig(8)

The getifaddrs() function first appeared in BSDI BSD/OS. The function has been available on OpenBSD since OpenBSD 2.7.

If both <net/if.h> and <ifaddrs.h> are being included, <net/if.h> be included before <ifaddrs.h>.

January 29, 2015 OpenBSD-5.8