lib/netdev.c

/*
 * TUN interface functions.
 * Copyright (C) 2002, 2003, 2004 Mondru AB.
 * Copyright (C) 2017-2018 by Harald Welte <laforge@gnumonks.org>
 *
 * The contents of this file may be used under the terms of the GNU
 * General Public License Version 2, provided that the above copyright
 * notice and this permission notice is included in all copies or
 * substantial portions of the software.
 *
 */

/*
 * netdev.c: Contains generic network device related functionality.
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <errno.h>
#include <net/route.h>
#include <net/if.h>

#if defined(__linux__)
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

#elif defined (__FreeBSD__)
#include <net/if_var.h>
#include <netinet/in_var.h>

#elif defined (__APPLE__)
#include <net/if.h>

#else
#error  "Unknown platform!"
#endif

#include "netdev.h"
#include "syserr.h"

#if defined(__linux__)

#include <linux/ipv6.h>

static int netdev_nlattr(struct nlmsghdr *n, int nsize, int type, void *d, int dlen)
{
	int len = RTA_LENGTH(dlen);
	int alen = NLMSG_ALIGN(n->nlmsg_len);
	struct rtattr *rta = (struct rtattr *)(((void *)n) + alen);
	if (alen + len > nsize)
		return -1;
	rta->rta_len = len;
	rta->rta_type = type;
	memcpy(RTA_DATA(rta), d, dlen);
	n->nlmsg_len = alen + len;
	return 0;
}
#endif

static int netdev_sifflags(const char *devname, int flags)
{
	struct ifreq ifr;
	int fd;

	memset(&ifr, '\0', sizeof(ifr));
	ifr.ifr_flags = flags;
	strncpy(ifr.ifr_name, devname, IFNAMSIZ);
	ifr.ifr_name[IFNAMSIZ - 1] = 0;	/* Make sure to terminate */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}
	if (ioctl(fd, SIOCSIFFLAGS, &ifr)) {
		SYS_ERR(DTUN, LOGL_ERROR, errno,
			"ioctl(SIOCSIFFLAGS) failed");
		close(fd);
		return -1;
	}
	close(fd);
	return 0;
}

int netdev_setaddr4(const char *devname, struct in_addr *addr,
		    struct in_addr *dstaddr, struct in_addr *netmask)
{
	struct ifreq ifr;
	int fd;

	memset(&ifr, '\0', sizeof(ifr));
	ifr.ifr_addr.sa_family = AF_INET;
	ifr.ifr_dstaddr.sa_family = AF_INET;

#if defined(__linux__)
	ifr.ifr_netmask.sa_family = AF_INET;

#elif defined(__FreeBSD__) || defined (__APPLE__)
	((struct sockaddr_in *)&ifr.ifr_addr)->sin_len =
	    sizeof(struct sockaddr_in);
	((struct sockaddr_in *)&ifr.ifr_dstaddr)->sin_len =
	    sizeof(struct sockaddr_in);
#endif

	strncpy(ifr.ifr_name, devname, IFNAMSIZ);
	ifr.ifr_name[IFNAMSIZ - 1] = 0;	/* Make sure to terminate */

	/* Create a channel to the NET kernel. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	if (addr) {		/* Set the interface address */
		memcpy(&((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr, addr,
		       sizeof(*addr));
		if (ioctl(fd, SIOCSIFADDR, (void *)&ifr) < 0) {
			if (errno != EEXIST) {
				SYS_ERR(DTUN, LOGL_ERROR, errno,
					"ioctl(SIOCSIFADDR) failed");
			} else {
				SYS_ERR(DTUN, LOGL_NOTICE, errno,
					"ioctl(SIOCSIFADDR): Address already exists");
			}
			close(fd);
			return -1;
		}
	}

	if (dstaddr) {		/* Set the destination address */
		memcpy(&((struct sockaddr_in *)&ifr.ifr_dstaddr)->sin_addr,
		       dstaddr, sizeof(*dstaddr));
		if (ioctl(fd, SIOCSIFDSTADDR, (caddr_t) & ifr) < 0) {
			SYS_ERR(DTUN, LOGL_ERROR, errno,
				"ioctl(SIOCSIFDSTADDR) failed");
			close(fd);
			return -1;
		}
	}

	if (netmask) {		/* Set the netmask */
#if defined(__linux__)
		memcpy(&((struct sockaddr_in *)&ifr.ifr_netmask)->sin_addr,
		       netmask, sizeof(*netmask));

#elif defined(__FreeBSD__) || defined (__APPLE__)
		((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr.s_addr =
		    netmask->s_addr;
#endif

		if (ioctl(fd, SIOCSIFNETMASK, (void *)&ifr) < 0) {
			SYS_ERR(DTUN, LOGL_ERROR, errno,
				"ioctl(SIOCSIFNETMASK) failed");
			close(fd);
			return -1;
		}
	}

	close(fd);

	/* On linux the route to the interface is set automatically
	   on FreeBSD we have to do this manually */

	/* TODO: How does it work on Solaris? */

	netdev_sifflags(devname, IFF_UP | IFF_RUNNING);

#if defined(__FreeBSD__) || defined (__APPLE__)
	netdev_addroute(dstaddr, addr, &this->netmask);
#endif

	return 0;
}

int netdev_setaddr6(const char *devname, struct in6_addr *addr, struct in6_addr *dstaddr,
		    size_t prefixlen)
{
	struct in6_ifreq ifr;
	int fd;

	memset(&ifr, 0, sizeof(ifr));

#if defined(__linux__)
	ifr.ifr6_prefixlen = prefixlen;
	ifr.ifr6_ifindex = if_nametoindex(devname);
	if (ifr.ifr6_ifindex == 0) {
		SYS_ERR(DTUN, LOGL_ERROR, 0, "Error getting ifindex for %s\n", devname);
		return -1;
	}
#elif defined(__FreeBSD__) || defined (__APPLE__)
	strncpy(ifr.ifr_name, devname, IFNAMSIZ);
#endif

	/* Create a channel to the NET kernel */
	if ((fd = socket(AF_INET6, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, 0, "socket() failed");
		return -1;
	}

#if defined(__linux__)
	if (addr) {
		memcpy(&ifr.ifr6_addr, addr, sizeof(*addr));
		if (ioctl(fd, SIOCSIFADDR, (void *) &ifr) < 0) {
			if (errno != EEXIST) {
				SYS_ERR(DTUN, LOGL_ERROR, 0, "ioctl(SIOCSIFADDR) failed");
			} else {
				SYS_ERR(DTUN, LOGL_NOTICE, 0, "ioctl(SIOCSIFADDR): Address already exists");
			}
			close(fd);
			return -1;
		}
	}

#if 0
	/* FIXME: looks like this is not possible/necessary for IPv6? */
	if (dstaddr) {
		memcpy(&ifr.ifr6_addr, dstaddr, sizeof(*dstaddr));
		if (ioctl(fd, SIOCSIFDSTADDR, (caddr_t *) &ifr) < 0) {
			SYS_ERR(DTUN, LOGL_ERROR, "ioctl(SIOCSIFDSTADDR) failed");
			close(fd);
			return -1;
		}
	}
#endif

#elif defined(__FreeBSD__) || defined (__APPLE__)
	if (addr)
		memcpy(&ifr.ifr_ifru.ifru_addr, addr, sizeof(ifr.ifr_ifru.ifru_addr));
	if (dstaddr)
		memcpy(&ifr.ifr_ifru.ifru_dstaddr, dstaddr, sizeof(ifr.ifr_ifru.ifru_dstaddr));

	if (ioctl(fd, SIOCSIFADDR_IN6, (struct ifreq *)&ifr) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, 0, "ioctl(SIOCSIFADDR_IN6) failed");
		close(fd);
		return -1;
	}
#endif

	close(fd);

	/* On linux the route to the interface is set automatically
	   on FreeBSD we have to do this manually */

	/* TODO: How does it work on Solaris? */

	netdev_sifflags(devname, IFF_UP | IFF_RUNNING);

#if 0	/* FIXME */
//#if defined(__FreeBSD__) || defined (__APPLE__)
	netdev_addroute6(dstaddr, addr, prefixlen);
#endif

	return 0;
}

int netdev_addaddr4(const char *devname, struct in_addr *addr,
		    struct in_addr *dstaddr, struct in_addr *netmask)
{

#if defined(__linux__)
	struct {
		struct nlmsghdr n;
		struct ifaddrmsg i;
		char buf[TUN_NLBUFSIZE];
	} req;

	struct sockaddr_nl local;
	socklen_t addr_len;
	int fd;
	int status;

	struct sockaddr_nl nladdr;
	struct iovec iov;
	struct msghdr msg;

	memset(&req, 0, sizeof(req));
	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
	req.n.nlmsg_type = RTM_NEWADDR;
	req.i.ifa_family = AF_INET;
	req.i.ifa_prefixlen = 32;	/* 32 FOR IPv4 */
	req.i.ifa_flags = 0;
	req.i.ifa_scope = RT_SCOPE_HOST;	/* TODO or 0 */
	req.i.ifa_index = if_nametoindex(devname);
	if (!req.i.ifa_index) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "Unable to get ifindex for %s", devname);
		return -1;
	}

	netdev_nlattr(&req.n, sizeof(req), IFA_ADDRESS, addr, sizeof(*addr));
	if (dstaddr)
		netdev_nlattr(&req.n, sizeof(req), IFA_LOCAL, dstaddr, sizeof(*dstaddr));

	if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	memset(&local, 0, sizeof(local));
	local.nl_family = AF_NETLINK;
	local.nl_groups = 0;

	if (bind(fd, (struct sockaddr *)&local, sizeof(local)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "bind() failed");
		close(fd);
		return -1;
	}

	addr_len = sizeof(local);
	if (getsockname(fd, (struct sockaddr *)&local, &addr_len) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno,
			"getsockname() failed");
		close(fd);
		return -1;
	}

	if (addr_len != sizeof(local)) {
		SYS_ERR(DTUN, LOGL_ERROR, 0,
			"Wrong address length %d", addr_len);
		close(fd);
		return -1;
	}

	if (local.nl_family != AF_NETLINK) {
		SYS_ERR(DTUN, LOGL_ERROR, 0,
			"Wrong address family %d", local.nl_family);
		close(fd);
		return -1;
	}

	iov.iov_base = (void *)&req.n;
	iov.iov_len = req.n.nlmsg_len;

	msg.msg_name = (void *)&nladdr;
	msg.msg_namelen = sizeof(nladdr);
	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	memset(&nladdr, 0, sizeof(nladdr));
	nladdr.nl_family = AF_NETLINK;
	nladdr.nl_pid = 0;
	nladdr.nl_groups = 0;

	req.n.nlmsg_seq = 0;
	req.n.nlmsg_flags |= NLM_F_ACK;

	status = sendmsg(fd, &msg, 0);
	if (status != req.n.nlmsg_len) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "sendmsg() failed, returned %d", status);
		close(fd);
		return -1;
	}

	status = netdev_sifflags(devname, IFF_UP | IFF_RUNNING);
	if (status == -1) {
		close(fd);
		return -1;
	}


	close(fd);
	return 0;

#elif defined (__FreeBSD__) || defined (__APPLE__)

	int fd;
	struct ifaliasreq areq;

	memset(&areq, 0, sizeof(areq));

	/* Set up interface name */
	strncpy(areq.ifra_name, devname, IFNAMSIZ);
	areq.ifra_name[IFNAMSIZ - 1] = 0;	/* Make sure to terminate */

	((struct sockaddr_in *)&areq.ifra_addr)->sin_family = AF_INET;
	((struct sockaddr_in *)&areq.ifra_addr)->sin_len =
	    sizeof(areq.ifra_addr);
	((struct sockaddr_in *)&areq.ifra_addr)->sin_addr.s_addr = addr->s_addr;

	((struct sockaddr_in *)&areq.ifra_mask)->sin_family = AF_INET;
	((struct sockaddr_in *)&areq.ifra_mask)->sin_len =
	    sizeof(areq.ifra_mask);
	((struct sockaddr_in *)&areq.ifra_mask)->sin_addr.s_addr =
	    netmask->s_addr;

	/* For some reason FreeBSD uses ifra_broadcast for specifying dstaddr */
	((struct sockaddr_in *)&areq.ifra_broadaddr)->sin_family = AF_INET;
	((struct sockaddr_in *)&areq.ifra_broadaddr)->sin_len =
	    sizeof(areq.ifra_broadaddr);
	((struct sockaddr_in *)&areq.ifra_broadaddr)->sin_addr.s_addr =
	    dstaddr->s_addr;

	/* Create a channel to the NET kernel. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	if (ioctl(fd, SIOCAIFADDR, (void *)&areq) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno,
			"ioctl(SIOCAIFADDR) failed");
		close(fd);
		return -1;
	}

	close(fd);
	return 0;

#endif

}

int netdev_addaddr6(const char *devname, struct in6_addr *addr,
		    struct in6_addr *dstaddr, int prefixlen)
{

#if defined(__linux__)
	struct {
		struct nlmsghdr n;
		struct ifaddrmsg i;
		char buf[TUN_NLBUFSIZE];
	} req;

	struct sockaddr_nl local;
	socklen_t addr_len;
	int fd;
	int status;

	struct sockaddr_nl nladdr;
	struct iovec iov;
	struct msghdr msg;

	memset(&req, 0, sizeof(req));
	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
	req.n.nlmsg_type = RTM_NEWADDR;
	req.i.ifa_family = AF_INET6;
	req.i.ifa_prefixlen = 64;	/* 64 FOR IPv6 */
	req.i.ifa_flags = 0;
	req.i.ifa_scope = RT_SCOPE_HOST;	/* TODO or 0 */
	req.i.ifa_index = if_nametoindex(devname);
	if (!req.i.ifa_index) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "Unable to get ifindex for %s", devname);
		return -1;
	}

	netdev_nlattr(&req.n, sizeof(req), IFA_ADDRESS, addr, sizeof(*addr));
	if (dstaddr)
		netdev_nlattr(&req.n, sizeof(req), IFA_LOCAL, dstaddr, sizeof(*dstaddr));

	if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	memset(&local, 0, sizeof(local));
	local.nl_family = AF_NETLINK;
	local.nl_groups = 0;

	if (bind(fd, (struct sockaddr *)&local, sizeof(local)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "bind() failed");
		close(fd);
		return -1;
	}

	addr_len = sizeof(local);
	if (getsockname(fd, (struct sockaddr *)&local, &addr_len) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno,
			"getsockname() failed");
		close(fd);
		return -1;
	}

	if (addr_len != sizeof(local)) {
		SYS_ERR(DTUN, LOGL_ERROR, 0,
			"Wrong address length %d", addr_len);
		close(fd);
		return -1;
	}

	if (local.nl_family != AF_NETLINK) {
		SYS_ERR(DTUN, LOGL_ERROR, 0,
			"Wrong address family %d", local.nl_family);
		close(fd);
		return -1;
	}

	iov.iov_base = (void *)&req.n;
	iov.iov_len = req.n.nlmsg_len;

	msg.msg_name = (void *)&nladdr;
	msg.msg_namelen = sizeof(nladdr);
	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_flags = 0;

	memset(&nladdr, 0, sizeof(nladdr));
	nladdr.nl_family = AF_NETLINK;
	nladdr.nl_pid = 0;
	nladdr.nl_groups = 0;

	req.n.nlmsg_seq = 0;
	req.n.nlmsg_flags |= NLM_F_ACK;

	status = sendmsg(fd, &msg, 0);
	if (status != req.n.nlmsg_len) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "sendmsg() failed, returned %d", status);
		close(fd);
		return -1;
	}

	status = netdev_sifflags(devname, IFF_UP | IFF_RUNNING);
	if (status == -1) {
		close(fd);
		return -1;
	}


	close(fd);
	return 0;

#elif defined (__FreeBSD__) || defined (__APPLE__)

	int fd;
	struct ifaliasreq areq;

	memset(&areq, 0, sizeof(areq));

	/* Set up interface name */
	strncpy(areq.ifra_name, devname, IFNAMSIZ);
	areq.ifra_name[IFNAMSIZ - 1] = 0;	/* Make sure to terminate */

	((struct sockaddr_in6 *)&areq.ifra_addr)->sin6_family = AF_INET6;
	((struct sockaddr_in6 *)&areq.ifra_addr)->sin6_len = sizeof(areq.ifra_addr);
	((struct sockaddr_in6 *)&areq.ifra_addr)->sin6_addr.s6_addr = addr->s6_addr;

	((struct sockaddr_in6 *)&areq.ifra_mask)->sin6_family = AF_INET6;
	((struct sockaddr_in6 *)&areq.ifra_mask)->sin6_len = sizeof(areq.ifra_mask);
	((struct sockaddr_in6 *)&areq.ifra_mask)->sin6_addr.s6_addr = netmask->s6_addr;

	/* For some reason FreeBSD uses ifra_broadcast for specifying dstaddr */
	((struct sockaddr_in6 *)&areq.ifra_broadaddr)->sin6_family = AF_INET6;
	((struct sockaddr_in6 *)&areq.ifra_broadaddr)->sin6_len = sizeof(areq.ifra_broadaddr);
	((struct sockaddr_in6 *)&areq.ifra_broadaddr)->sin6_addr.s6_addr = dstaddr->s6_addr;

	/* Create a channel to the NET kernel. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	if (ioctl(fd, SIOCAIFADDR, (void *)&areq) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno,
			"ioctl(SIOCAIFADDR) failed");
		close(fd);
		return -1;
	}

	close(fd);
	return 0;

#endif

}

static int netdev_route(struct in_addr *dst, struct in_addr *gateway, struct in_addr *mask, int delete)
{

#if defined(__linux__)

	struct rtentry r;
	int fd;

	memset(&r, '\0', sizeof(r));
	r.rt_flags = RTF_UP | RTF_GATEWAY;	/* RTF_HOST not set */

	/* Create a channel to the NET kernel. */
	if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	r.rt_dst.sa_family = AF_INET;
	r.rt_gateway.sa_family = AF_INET;
	r.rt_genmask.sa_family = AF_INET;
	memcpy(&((struct sockaddr_in *)&r.rt_dst)->sin_addr, dst, sizeof(*dst));
	memcpy(&((struct sockaddr_in *)&r.rt_gateway)->sin_addr, gateway,
	       sizeof(*gateway));
	memcpy(&((struct sockaddr_in *)&r.rt_genmask)->sin_addr, mask,
	       sizeof(*mask));

	if (delete) {
		if (ioctl(fd, SIOCDELRT, (void *)&r) < 0) {
			SYS_ERR(DTUN, LOGL_ERROR, errno,
				"ioctl(SIOCDELRT) failed");
			close(fd);
			return -1;
		}
	} else {
		if (ioctl(fd, SIOCADDRT, (void *)&r) < 0) {
			SYS_ERR(DTUN, LOGL_ERROR, errno,
				"ioctl(SIOCADDRT) failed");
			close(fd);
			return -1;
		}
	}
	close(fd);
	return 0;

#elif defined(__FreeBSD__) || defined (__APPLE__)

	struct {
		struct rt_msghdr rt;
		struct sockaddr_in dst;
		struct sockaddr_in gate;
		struct sockaddr_in mask;
	} req;

	int fd;
	struct rt_msghdr *rtm;

	if ((fd = socket(AF_ROUTE, SOCK_RAW, 0)) == -1) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "socket() failed");
		return -1;
	}

	memset(&req, 0x00, sizeof(req));

	rtm = &req.rt;

	rtm->rtm_msglen = sizeof(req);
	rtm->rtm_version = RTM_VERSION;
	if (delete) {
		rtm->rtm_type = RTM_DELETE;
	} else {
		rtm->rtm_type = RTM_ADD;
	}
	rtm->rtm_flags = RTF_UP | RTF_GATEWAY | RTF_STATIC;	/* TODO */
	rtm->rtm_addrs = RTA_DST | RTA_GATEWAY | RTA_NETMASK;
	rtm->rtm_pid = getpid();
	rtm->rtm_seq = 0044;	/* TODO */

	req.dst.sin_family = AF_INET;
	req.dst.sin_len = sizeof(req.dst);
	req.mask.sin_family = AF_INET;
	req.mask.sin_len = sizeof(req.mask);
	req.gate.sin_family = AF_INET;
	req.gate.sin_len = sizeof(req.gate);

	req.dst.sin_addr.s_addr = dst->s_addr;
	req.mask.sin_addr.s_addr = mask->s_addr;
	req.gate.sin_addr.s_addr = gateway->s_addr;

	if (write(fd, rtm, rtm->rtm_msglen) < 0) {
		SYS_ERR(DTUN, LOGL_ERROR, errno, "write() failed");
		close(fd);
		return -1;
	}
	close(fd);
	return 0;
#endif

}

int netdev_addroute(struct in_addr *dst, struct in_addr *gateway, struct in_addr *mask)
{
	return netdev_route(dst, gateway, mask, 0);
}

int netdev_delroute(struct in_addr *dst, struct in_addr *gateway, struct in_addr *mask)
{
	return netdev_route(dst, gateway, mask, 1);
}

#include <ifaddrs.h>

/*! Obtain the local address of a network device
 *  \param[in] devname Target device owning the IP
 *  \param[out] prefix_list List of prefix structures to fill with each IPv4/6 and prefix length found.
 *  \param[in] prefix_size Amount of elements allowed to be fill in the prefix_list array.
 *  \param[in] flags Specify which kind of IP to look for: IP_TYPE_IPv4, IP_TYPE_IPv6_LINK, IP_TYPE_IPv6_NONLINK
 *  \returns The number of ips found following the criteria specified by flags, -1 on error.
 *
 * This function will fill prefix_list with up to prefix_size IPs following the
 * criteria specified by flags parameter. It returns the number of IPs matching
 * the criteria. As a result, the number returned can be bigger than
 * prefix_size. It can be used with prefix_size=0 to get an estimate of the size
 * needed for prefix_list.
 */
int netdev_ip_local_get(const char *devname, struct in46_prefix *prefix_list, size_t prefix_size, int flags)
{
	static const uint8_t ll_prefix[] = { 0xfe,0x80, 0,0, 0,0, 0,0 };
	struct ifaddrs *ifaddr, *ifa;
	struct in46_addr netmask;
	size_t count = 0;
	bool is_ipv6_ll;

	if (getifaddrs(&ifaddr) == -1) {
		return -1;
	}

	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
		if (ifa->ifa_addr == NULL)
			continue;

		if (strcmp(ifa->ifa_name, devname))
			continue;

		if (ifa->ifa_addr->sa_family == AF_INET && (flags & IP_TYPE_IPv4)) {
			struct sockaddr_in *sin4 = (struct sockaddr_in *) ifa->ifa_addr;
			struct sockaddr_in *netmask4 = (struct sockaddr_in *) ifa->ifa_netmask;

			if (count < prefix_size) {
				netmask.len = sizeof(netmask4->sin_addr);
				netmask.v4 = netmask4->sin_addr;
				prefix_list[count].addr.len = sizeof(sin4->sin_addr);
				prefix_list[count].addr.v4 = sin4->sin_addr;
				prefix_list[count].prefixlen = in46a_netmasklen(&netmask);
			}
			count++;
		}

		if (ifa->ifa_addr->sa_family == AF_INET6 && (flags & IP_TYPE_IPv6)) {
			struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) ifa->ifa_addr;
			struct sockaddr_in6 *netmask6 = (struct sockaddr_in6 *) ifa->ifa_netmask;

			is_ipv6_ll = !memcmp(sin6->sin6_addr.s6_addr, ll_prefix, sizeof(ll_prefix));
			if ((flags & IP_TYPE_IPv6_NONLINK) && is_ipv6_ll)
				continue;
			if ((flags & IP_TYPE_IPv6_LINK) && !is_ipv6_ll)
				continue;

			if (count < prefix_size) {
				netmask.len = sizeof(netmask6->sin6_addr);
				netmask.v6 = netmask6->sin6_addr;
				prefix_list[count].addr.len = sizeof(sin6->sin6_addr);
				prefix_list[count].addr.v6 = sin6->sin6_addr;
				prefix_list[count].prefixlen = in46a_netmasklen(&netmask);
			}
			count++;
		}
	}

	freeifaddrs(ifaddr);
	return count;
}