GETIFADDRS(3) | Library Functions Manual | GETIFADDRS(3)

# 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 *ifp);

# 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 */

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 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.

# EXAMPLES

The following example program prints a list of all addresses configured on the system.

    #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;
    }

# 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

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

# HISTORY

The getifaddrs implementation first appeared in BSD/OS.

# BUGS

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

April 7, 2013 | NetBSD 7.2