kernel-netlink: Support extended table IDs for custom routes

[strongswan.git] / src / libcharon / plugins / kernel_netlink / kernel_netlink_net.c

/*
 * Copyright (C) 2008-2019 Tobias Brunner
 * Copyright (C) 2005-2008 Martin Willi
 * HSR Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

/*
 * Copyright (C) 2010 secunet Security Networks AG
 * Copyright (C) 2010 Thomas Egerer
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <sys/socket.h>
#include <sys/utsname.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/if_addrlabel.h>
#include <unistd.h>
#include <errno.h>
#include <net/if.h>
#ifdef HAVE_LINUX_FIB_RULES_H
#include <linux/fib_rules.h>
#endif

#include "kernel_netlink_net.h"
#include "kernel_netlink_shared.h"

#include <daemon.h>
#include <utils/debug.h>
#include <threading/mutex.h>
#include <threading/rwlock.h>
#include <threading/rwlock_condvar.h>
#include <threading/spinlock.h>
#include <collections/hashtable.h>
#include <collections/linked_list.h>
#include <processing/jobs/callback_job.h>

/** delay before firing roam events (ms) */
#define ROAM_DELAY 100

/** delay before reinstalling routes (ms) */
#define ROUTE_DELAY 100

/** maximum recursion when searching for addresses in get_route() */
#define MAX_ROUTE_RECURSION 2

#ifndef ROUTING_TABLE
#define ROUTING_TABLE 0
#endif

#ifndef ROUTING_TABLE_PRIO
#define ROUTING_TABLE_PRIO 0
#endif

/** multicast groups (for groups > 31 setsockopt has to be used) */
#define nl_group(group) (1 << (group - 1))

ENUM(rt_msg_names, RTM_NEWLINK, RTM_GETRULE,
        "RTM_NEWLINK",
        "RTM_DELLINK",
        "RTM_GETLINK",
        "RTM_SETLINK",
        "RTM_NEWADDR",
        "RTM_DELADDR",
        "RTM_GETADDR",
        "31",
        "RTM_NEWROUTE",
        "RTM_DELROUTE",
        "RTM_GETROUTE",
        "35",
        "RTM_NEWNEIGH",
        "RTM_DELNEIGH",
        "RTM_GETNEIGH",
        "RTM_NEWRULE",
        "RTM_DELRULE",
        "RTM_GETRULE",
);

typedef struct addr_entry_t addr_entry_t;

/**
 * IP address in an iface_entry_t
 */
struct addr_entry_t {

        /** the ip address */
        host_t *ip;

        /** address flags */
        u_char flags;

        /** scope of the address */
        u_char scope;

        /** number of times this IP is used, if virtual (i.e. managed by us) */
        u_int refcount;

        /** TRUE once it is installed, if virtual */
        bool installed;
};

/**
 * destroy a addr_entry_t object
 */
static void addr_entry_destroy(addr_entry_t *this)
{
        this->ip->destroy(this->ip);
        free(this);
}

typedef struct iface_entry_t iface_entry_t;

/**
 * A network interface on this system, containing addr_entry_t's
 */
struct iface_entry_t {

        /** interface index */
        int ifindex;

        /** name of the interface */
        char ifname[IFNAMSIZ];

        /** interface flags, as in netdevice(7) SIOCGIFFLAGS */
        u_int flags;

        /** list of addresses as host_t */
        linked_list_t *addrs;

        /** TRUE if usable by config */
        bool usable;
};

/**
 * destroy an interface entry
 */
static void iface_entry_destroy(iface_entry_t *this)
{
        this->addrs->destroy_function(this->addrs, (void*)addr_entry_destroy);
        free(this);
}

CALLBACK(iface_entry_by_index, bool,
        iface_entry_t *this, va_list args)
{
        int ifindex;

        VA_ARGS_VGET(args, ifindex);
        return this->ifindex == ifindex;
}

CALLBACK(iface_entry_by_name, bool,
        iface_entry_t *this, va_list args)
{
        char *ifname;

        VA_ARGS_VGET(args, ifname);
        return streq(this->ifname, ifname);
}

/**
 * check if an interface is up
 */
static inline bool iface_entry_up(iface_entry_t *iface)
{
        return (iface->flags & IFF_UP) == IFF_UP;
}

/**
 * check if an interface is up and usable
 */
static inline bool iface_entry_up_and_usable(iface_entry_t *iface)
{
        return iface->usable && iface_entry_up(iface);
}

typedef struct addr_map_entry_t addr_map_entry_t;

/**
 * Entry that maps an IP address to an interface entry
 */
struct addr_map_entry_t {
        /** The IP address */
        host_t *ip;

        /** The address entry for this IP address */
        addr_entry_t *addr;

        /** The interface this address is installed on */
        iface_entry_t *iface;
};

/**
 * Hash a addr_map_entry_t object, all entries with the same IP address
 * are stored in the same bucket
 */
static u_int addr_map_entry_hash(addr_map_entry_t *this)
{
        return chunk_hash(this->ip->get_address(this->ip));
}

/**
 * Compare two addr_map_entry_t objects, two entries are equal if they are
 * installed on the same interface
 */
static bool addr_map_entry_equals(addr_map_entry_t *a, addr_map_entry_t *b)
{
        return a->iface->ifindex == b->iface->ifindex &&
                   a->ip->ip_equals(a->ip, b->ip);
}

/**
 * Used with get_match this finds an address entry if it is installed on
 * an up and usable interface
 */
static bool addr_map_entry_match_up_and_usable(addr_map_entry_t *a,
                                                                                           addr_map_entry_t *b)
{
        return iface_entry_up_and_usable(b->iface) &&
                   a->ip->ip_equals(a->ip, b->ip);
}

/**
 * Used with get_match this finds an address entry if it is installed on
 * any active local interface
 */
static bool addr_map_entry_match_up(addr_map_entry_t *a, addr_map_entry_t *b)
{
        return iface_entry_up(b->iface) && a->ip->ip_equals(a->ip, b->ip);
}

/**
 * Used with get_match this finds an address entry if it is installed on
 * any local interface
 */
static bool addr_map_entry_match(addr_map_entry_t *a, addr_map_entry_t *b)
{
        return a->ip->ip_equals(a->ip, b->ip);
}

typedef struct route_entry_t route_entry_t;

/**
 * Installed routing entry
 */
struct route_entry_t {
        /** Name of the interface the route is bound to */
        char *if_name;

        /** Source ip of the route */
        host_t *src_ip;

        /** Gateway for this route */
        host_t *gateway;

        /** Destination net */
        chunk_t dst_net;

        /** Destination net prefixlen */
        uint8_t prefixlen;
};

/**
 * Clone a route_entry_t object.
 */
static route_entry_t *route_entry_clone(route_entry_t *this)
{
        route_entry_t *route;

        INIT(route,
                .if_name = strdup(this->if_name),
                .src_ip = this->src_ip->clone(this->src_ip),
                .gateway = this->gateway ? this->gateway->clone(this->gateway) : NULL,
                .dst_net = chunk_clone(this->dst_net),
                .prefixlen = this->prefixlen,
        );
        return route;
}

/**
 * Destroy a route_entry_t object
 */
static void route_entry_destroy(route_entry_t *this)
{
        free(this->if_name);
        DESTROY_IF(this->src_ip);
        DESTROY_IF(this->gateway);
        chunk_free(&this->dst_net);
        free(this);
}

/**
 * Hash a route_entry_t object
 */
static u_int route_entry_hash(route_entry_t *this)
{
        return chunk_hash_inc(chunk_from_thing(this->prefixlen),
                                                  chunk_hash(this->dst_net));
}

/**
 * Compare two route_entry_t objects
 */
static bool route_entry_equals(route_entry_t *a, route_entry_t *b)
{
        if (a->if_name && b->if_name && streq(a->if_name, b->if_name) &&
                a->src_ip->ip_equals(a->src_ip, b->src_ip) &&
                chunk_equals(a->dst_net, b->dst_net) && a->prefixlen == b->prefixlen)
        {
                return (!a->gateway && !b->gateway) || (a->gateway && b->gateway &&
                                        a->gateway->ip_equals(a->gateway, b->gateway));
        }
        return FALSE;
}

typedef struct net_change_t net_change_t;

/**
 * Queued network changes
 */
struct net_change_t {
        /** Name of the interface that got activated (or an IP appeared on) */
        char *if_name;
};

/**
 * Destroy a net_change_t object
 */
static void net_change_destroy(net_change_t *this)
{
        free(this->if_name);
        free(this);
}

/**
 * Hash a net_change_t object
 */
static u_int net_change_hash(net_change_t *this)
{
        return chunk_hash(chunk_create(this->if_name, strlen(this->if_name)));
}

/**
 * Compare two net_change_t objects
 */
static bool net_change_equals(net_change_t *a, net_change_t *b)
{
        return streq(a->if_name, b->if_name);
}

typedef struct private_kernel_netlink_net_t private_kernel_netlink_net_t;

/**
 * Private variables and functions of kernel_netlink_net class.
 */
struct private_kernel_netlink_net_t {
        /**
         * Public part of the kernel_netlink_net_t object.
         */
        kernel_netlink_net_t public;

        /**
         * lock to access various lists and maps
         */
        rwlock_t *lock;

        /**
         * condition variable to signal virtual IP add/removal
         */
        rwlock_condvar_t *condvar;

        /**
         * Cached list of interfaces and its addresses (iface_entry_t)
         */
        linked_list_t *ifaces;

        /**
         * Map for IP addresses to iface_entry_t objects (addr_map_entry_t)
         */
        hashtable_t *addrs;

        /**
         * Map for virtual IP addresses to iface_entry_t objects (addr_map_entry_t)
         */
        hashtable_t *vips;

        /**
         * netlink rt socket (routing)
         */
        netlink_socket_t *socket;

        /**
         * Netlink rt socket to receive address change events
         */
        int socket_events;

        /**
         * earliest time of the next roam event
         */
        timeval_t next_roam;

        /**
         * roam event due to address change
         */
        bool roam_address;

        /**
         * lock to check and update roam event time
         */
        spinlock_t *roam_lock;

        /**
         * routing table to install routes
         */
        uint32_t routing_table;

        /**
         * priority of used routing table
         */
        uint32_t routing_table_prio;

        /**
         * installed routes
         */
        hashtable_t *routes;

        /**
         * mutex for routes
         */
        mutex_t *routes_lock;

        /**
         * interface changes which may trigger route reinstallation
         */
        hashtable_t *net_changes;

        /**
         * mutex for route reinstallation triggers
         */
        mutex_t *net_changes_lock;

        /**
         * time of last route reinstallation
         */
        timeval_t last_route_reinstall;

        /**
         * whether to react to RTM_NEWROUTE or RTM_DELROUTE events
         */
        bool process_route;

        /**
         * whether to react to RTM_NEWRULE or RTM_DELRULE events
         */
        bool process_rules;

        /**
         * whether to trigger roam events
         */
        bool roam_events;

        /**
         * whether to install IPsec policy routes
         */
        bool install_routes;

        /**
         * whether to actually install virtual IPs
         */
        bool install_virtual_ip;

        /**
         * the name of the interface virtual IP addresses are installed on
         */
        char *install_virtual_ip_on;

        /**
         * whether preferred source addresses can be specified for IPv6 routes
         */
        bool rta_prefsrc_for_ipv6;

        /**
         * whether marks can be used in route lookups
         */
        bool rta_mark;

        /**
         * the mark excluded from the routing rule used for virtual IPs
         */
        mark_t routing_mark;

        /**
         * whether to prefer temporary IPv6 addresses over public ones
         */
        bool prefer_temporary_addrs;

        /**
         * list with routing tables to be excluded from route lookup
         */
        linked_list_t *rt_exclude;

        /**
         * MTU to set on installed routes
         */
        uint32_t mtu;

        /**
         * MSS to set on installed routes
         */
        uint32_t mss;
};

/**
 * Forward declaration
 */
static status_t manage_srcroute(private_kernel_netlink_net_t *this,
                                                                int nlmsg_type, int flags, chunk_t dst_net,
                                                                uint8_t prefixlen, host_t *gateway,
                                                                host_t *src_ip, char *if_name);

/**
 * Clear the queued network changes.
 */
static void net_changes_clear(private_kernel_netlink_net_t *this)
{
        enumerator_t *enumerator;
        net_change_t *change;

        enumerator = this->net_changes->create_enumerator(this->net_changes);
        while (enumerator->enumerate(enumerator, NULL, (void**)&change))
        {
                this->net_changes->remove_at(this->net_changes, enumerator);
                net_change_destroy(change);
        }
        enumerator->destroy(enumerator);
}

/**
 * Act upon queued network changes.
 */
static job_requeue_t reinstall_routes(private_kernel_netlink_net_t *this)
{
        enumerator_t *enumerator;
        route_entry_t *route;

        this->net_changes_lock->lock(this->net_changes_lock);
        this->routes_lock->lock(this->routes_lock);

        enumerator = this->routes->create_enumerator(this->routes);
        while (enumerator->enumerate(enumerator, NULL, (void**)&route))
        {
                net_change_t *change, lookup = {
                        .if_name = route->if_name,
                };
                /* check if a change for the outgoing interface is queued */
                change = this->net_changes->get(this->net_changes, &lookup);
                if (!change)
                {       /* in case src_ip is not on the outgoing interface */
                        if (this->public.interface.get_interface(&this->public.interface,
                                                                                                route->src_ip, &lookup.if_name))
                        {
                                if (!streq(lookup.if_name, route->if_name))
                                {
                                        change = this->net_changes->get(this->net_changes, &lookup);
                                }
                                free(lookup.if_name);
                        }
                }
                if (change)
                {
                        manage_srcroute(this, RTM_NEWROUTE, NLM_F_CREATE | NLM_F_EXCL,
                                                        route->dst_net, route->prefixlen, route->gateway,
                                                        route->src_ip, route->if_name);
                }
        }
        enumerator->destroy(enumerator);
        this->routes_lock->unlock(this->routes_lock);

        net_changes_clear(this);
        this->net_changes_lock->unlock(this->net_changes_lock);
        return JOB_REQUEUE_NONE;
}

/**
 * Queue route reinstallation caused by network changes for a given interface.
 *
 * The route reinstallation is delayed for a while and only done once for
 * several calls during this delay, in order to avoid doing it too often.
 * The interface name is freed.
 */
static void queue_route_reinstall(private_kernel_netlink_net_t *this,
                                                                  char *if_name)
{
        net_change_t *update, *found;
        timeval_t now;
        job_t *job;

        INIT(update,
                .if_name = if_name
        );

        this->net_changes_lock->lock(this->net_changes_lock);
        found = this->net_changes->put(this->net_changes, update, update);
        if (found)
        {
                net_change_destroy(found);
        }
        time_monotonic(&now);
        if (timercmp(&now, &this->last_route_reinstall, >))
        {
                timeval_add_ms(&now, ROUTE_DELAY);
                this->last_route_reinstall = now;

                job = (job_t*)callback_job_create((callback_job_cb_t)reinstall_routes,
                                                                                  this, NULL, NULL);
                lib->scheduler->schedule_job_ms(lib->scheduler, job, ROUTE_DELAY);
        }
        this->net_changes_lock->unlock(this->net_changes_lock);
}

/**
 * check if the given IP is known as virtual IP and currently installed
 *
 * this function will also return TRUE if the virtual IP entry disappeared.
 * in that case the returned entry will be NULL.
 *
 * this->lock must be held when calling this function
 */
static bool is_vip_installed_or_gone(private_kernel_netlink_net_t *this,
                                                                         host_t *ip, addr_map_entry_t **entry)
{
        addr_map_entry_t lookup = {
                .ip = ip,
        };

        *entry = this->vips->get_match(this->vips, &lookup,
                                                                  (void*)addr_map_entry_match);
        if (*entry == NULL)
        {       /* the virtual IP disappeared */
                return TRUE;
        }
        return (*entry)->addr->installed;
}

/**
 * check if the given IP is known as virtual IP
 *
 * this->lock must be held when calling this function
 */
static bool is_known_vip(private_kernel_netlink_net_t *this, host_t *ip)
{
        addr_map_entry_t lookup = {
                .ip = ip,
        };

        return this->vips->get_match(this->vips, &lookup,
                                                                (void*)addr_map_entry_match) != NULL;
}

/**
 * Add an address map entry
 */
static void addr_map_entry_add(hashtable_t *map, addr_entry_t *addr,
                                                           iface_entry_t *iface)
{
        addr_map_entry_t *entry;

        INIT(entry,
                .ip = addr->ip,
                .addr = addr,
                .iface = iface,
        );
        entry = map->put(map, entry, entry);
        free(entry);
}

/**
 * Remove an address map entry
 */
static void addr_map_entry_remove(hashtable_t *map, addr_entry_t *addr,
                                                                  iface_entry_t *iface)
{
        addr_map_entry_t *entry, lookup = {
                .ip = addr->ip,
                .addr = addr,
                .iface = iface,
        };

        entry = map->remove(map, &lookup);
        free(entry);
}

/**
 * Check if an address or net (addr with prefix net bits) is in
 * subnet (net with net_len net bits)
 */
static bool addr_in_subnet(chunk_t addr, int prefix, chunk_t net, int net_len)
{
        static const u_char mask[] = { 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe };
        int byte = 0;

        if (net_len == 0)
        {       /* any address matches a /0 network */
                return TRUE;
        }
        if (addr.len != net.len || net_len > 8 * net.len || prefix < net_len)
        {
                return FALSE;
        }
        /* scan through all bytes in network order */
        while (net_len > 0)
        {
                if (net_len < 8)
                {
                        return (mask[net_len] & addr.ptr[byte]) == (mask[net_len] & net.ptr[byte]);
                }
                else
                {
                        if (addr.ptr[byte] != net.ptr[byte])
                        {
                                return FALSE;
                        }
                        byte++;
                        net_len -= 8;
                }
        }
        return TRUE;
}

/**
 * Check if the given address is in subnet (net with net_len net bits)
 */
static bool host_in_subnet(host_t *host, chunk_t net, int net_len)
{
        chunk_t addr;

        addr = host->get_address(host);
        return addr_in_subnet(addr, addr.len * 8, net, net_len);
}

/**
 * Determine the type or scope of the given unicast IP address.  This is not
 * the same thing returned in rtm_scope/ifa_scope.
 *
 * We use return values as defined in RFC 6724 (referring to RFC 4291).
 */
static u_char get_scope(host_t *ip)
{
        chunk_t addr;

        addr = ip->get_address(ip);
        switch (addr.len)
        {
                case 4:
                        /* we use the mapping defined in RFC 6724, 3.2 */
                        if (addr.ptr[0] == 127)
                        {       /* link-local, same as the IPv6 loopback address */
                                return 2;
                        }
                        if (addr.ptr[0] == 169 && addr.ptr[1] == 254)
                        {       /* link-local */
                                return 2;
                        }
                        break;
                case 16:
                        if (IN6_IS_ADDR_LOOPBACK((struct in6_addr*)addr.ptr))
                        {       /* link-local, according to RFC 4291, 2.5.3 */
                                return 2;
                        }
                        if (IN6_IS_ADDR_LINKLOCAL((struct in6_addr*)addr.ptr))
                        {
                                return 2;
                        }
                        if (IN6_IS_ADDR_SITELOCAL((struct in6_addr*)addr.ptr))
                        {       /* deprecated, according to RFC 4291, 2.5.7 */
                                return 5;
                        }
                        break;
                default:
                        break;
        }
        /* global */
        return 14;
}

/**
 * Determine the label of the given unicast IP address.
 *
 * We currently only support the default table given in RFC 6724:
 *
 *  Prefix        Precedence Label
 *  ::1/128               50     0
 *  ::/0                  40     1
 *  ::ffff:0:0/96         35     4
 *  2002::/16             30     2
 *  2001::/32              5     5
 *  fc00::/7               3    13
 *  ::/96                  1     3
 *  fec0::/10              1    11
 *  3ffe::/16              1    12
 */
static u_char get_label(host_t *ip)
{
        struct {
                chunk_t net;
                u_char prefix;
                u_char label;
        } priorities[] = {
                /* priority table ordered by prefix */
                /* ::1/128 */
                { chunk_from_chars(0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01), 128, 0 },
                /* ::ffff:0:0/96 */
                { chunk_from_chars(0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00), 96, 4 },
                /* ::/96 */
                { chunk_from_chars(0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 96, 3 },
                /* 2001::/32 */
                { chunk_from_chars(0x20, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 32, 5 },
                /* 2002::/16 */
                { chunk_from_chars(0x20, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 16, 2 },
                /* 3ffe::/16 */
                { chunk_from_chars(0x3f, 0xfe, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 16, 12 },
                /* fec0::/10 */
                { chunk_from_chars(0xfe, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 10, 11 },
                /* fc00::/7 */
                { chunk_from_chars(0xfc, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00), 7, 13 },
        };
        int i;

        for (i = 0; i < countof(priorities); i++)
        {
                if (host_in_subnet(ip, priorities[i].net, priorities[i].prefix))
                {
                        return priorities[i].label;
                }
        }
        /* ::/0 */
        return 1;
}

/**
 * Returns the length of the common prefix in bits up to the length of a's
 * prefix, defined by RFC 6724 as the portion of the address not including the
 * interface ID, which is 64-bit for most unicast addresses (see RFC 4291).
 */
static u_char common_prefix(host_t *a, host_t *b)
{
        chunk_t aa, ba;
        u_char byte, bits = 0, match;

        aa = a->get_address(a);
        ba = b->get_address(b);
        for (byte = 0; byte < 8; byte++)
        {
                if (aa.ptr[byte] != ba.ptr[byte])
                {
                        match = aa.ptr[byte] ^ ba.ptr[byte];
                        for (bits = 8; match; match >>= 1)
                        {
                                bits--;
                        }
                        break;
                }
        }
        return byte * 8 + bits;
}

/**
 * Compare two IP addresses and return TRUE if the second address is the better
 * choice of the two to reach the destination.
 * For IPv6 we approximately follow RFC 6724.
 */
static bool is_address_better(private_kernel_netlink_net_t *this,
                                                          addr_entry_t *a, addr_entry_t *b, host_t *d)
{
        u_char sa, sb, sd, la, lb, ld, pa, pb;

        /* rule 2: prefer appropriate scope */
        if (d)
        {
                sa = get_scope(a->ip);
                sb = get_scope(b->ip);
                sd = get_scope(d);
                if (sa < sb)
                {
                        return sa < sd;
                }
                else if (sb < sa)
                {
                        return sb >= sd;
                }
        }
        if (a->ip->get_family(a->ip) == AF_INET)
        {       /* stop here for IPv4, default to addresses found earlier */
                return FALSE;
        }
        /* rule 3: avoid deprecated addresses (RFC 4862) */
        if ((a->flags & IFA_F_DEPRECATED) != (b->flags & IFA_F_DEPRECATED))
        {
                return a->flags & IFA_F_DEPRECATED;
        }
        /* rule 4 is not applicable as we don't know if an address is a home or
         * care-of addresses.
         * rule 5 does not apply as we only compare addresses from one interface
         */
        /* rule 6: prefer matching label */
        if (d)
        {
                la = get_label(a->ip);
                lb = get_label(b->ip);
                ld = get_label(d);
                if (la == ld && lb != ld)
                {
                        return FALSE;
                }
                else if (lb == ld && la != ld)
                {
                        return TRUE;
                }
        }
        /* rule 7: prefer temporary addresses (WE REVERSE THIS BY DEFAULT!) */
        if ((a->flags & IFA_F_TEMPORARY) != (b->flags & IFA_F_TEMPORARY))
        {
                if (this->prefer_temporary_addrs)
                {
                        return b->flags & IFA_F_TEMPORARY;
                }
                return a->flags & IFA_F_TEMPORARY;
        }
        /* rule 8: use longest matching prefix */
        if (d)
        {
                pa = common_prefix(a->ip, d);
                pb = common_prefix(b->ip, d);
                if (pa != pb)
                {
                        return pb > pa;
                }
        }
        /* default to addresses found earlier */
        return FALSE;
}

/**
 * Get a non-virtual IP address on the given interfaces and optionally in a
 * given subnet.
 *
 * If a candidate address is given, we first search for that address and if not
 * found return the address as above.
 * Returned host is a clone, has to be freed by caller.
 *
 * this->lock must be held when calling this function.
 */
static host_t *get_matching_address(private_kernel_netlink_net_t *this,
                                                                        int *ifindex, int family, chunk_t net,
                                                                        uint8_t mask, host_t *dest,
                                                                        host_t *candidate)
{
        enumerator_t *ifaces, *addrs;
        iface_entry_t *iface;
        addr_entry_t *addr, *best = NULL;
        bool candidate_matched = FALSE;

        ifaces = this->ifaces->create_enumerator(this->ifaces);
        while (ifaces->enumerate(ifaces, &iface))
        {
                if (iface->usable && (!ifindex || iface->ifindex == *ifindex))
                {       /* only use matching interfaces not excluded by config */
                        addrs = iface->addrs->create_enumerator(iface->addrs);
                        while (addrs->enumerate(addrs, &addr))
                        {
                                if (addr->refcount ||
                                        addr->ip->get_family(addr->ip) != family)
                                {       /* ignore virtual IP addresses and ensure family matches */
                                        continue;
                                }
                                if (net.ptr && !host_in_subnet(addr->ip, net, mask))
                                {       /* optionally match a subnet */
                                        continue;
                                }
                                if (candidate && candidate->ip_equals(candidate, addr->ip))
                                {       /* stop if we find the candidate */
                                        best = addr;
                                        candidate_matched = TRUE;
                                        break;
                                }
                                else if (!best || is_address_better(this, best, addr, dest))
                                {
                                        best = addr;
                                }
                        }
                        addrs->destroy(addrs);
                        if (ifindex || candidate_matched)
                        {
                                break;
                        }
                }
        }
        ifaces->destroy(ifaces);
        return best ? best->ip->clone(best->ip) : NULL;
}

/**
 * Get a non-virtual IP address on the given interface.
 *
 * If a candidate address is given, we first search for that address and if not
 * found return the address as above.
 * Returned host is a clone, has to be freed by caller.
 *
 * this->lock must be held when calling this function.
 */
static host_t *get_interface_address(private_kernel_netlink_net_t *this,
                                                                         int ifindex, int family, host_t *dest,
                                                                         host_t *candidate)
{
        return get_matching_address(this, &ifindex, family, chunk_empty, 0, dest,
                                                                candidate);
}

/**
 * Get a non-virtual IP address in the given subnet.
 *
 * If a candidate address is given, we first search for that address and if not
 * found return the address as above.
 * Returned host is a clone, has to be freed by caller.
 *
 * this->lock must be held when calling this function.
 */
static host_t *get_subnet_address(private_kernel_netlink_net_t *this,
                                                                  int family, chunk_t net, uint8_t mask,
                                                                  host_t *dest, host_t *candidate)
{
        return get_matching_address(this, NULL, family, net, mask, dest, candidate);
}

/**
 * callback function that raises the delayed roam event
 */
static job_requeue_t roam_event(private_kernel_netlink_net_t *this)
{
        bool address;

        this->roam_lock->lock(this->roam_lock);
        address = this->roam_address;
        this->roam_address = FALSE;
        this->roam_lock->unlock(this->roam_lock);
        charon->kernel->roam(charon->kernel, address);
        return JOB_REQUEUE_NONE;
}

/**
 * fire a roaming event. we delay it for a bit and fire only one event
 * for multiple calls. otherwise we would create too many events.
 */
static void fire_roam_event(private_kernel_netlink_net_t *this, bool address)
{
        timeval_t now;
        job_t *job;

        if (!this->roam_events)
        {
                return;
        }

        time_monotonic(&now);
        this->roam_lock->lock(this->roam_lock);
        this->roam_address |= address;
        if (!timercmp(&now, &this->next_roam, >))
        {
                this->roam_lock->unlock(this->roam_lock);
                return;
        }
        timeval_add_ms(&now, ROAM_DELAY);
        this->next_roam = now;
        this->roam_lock->unlock(this->roam_lock);

        job = (job_t*)callback_job_create((callback_job_cb_t)roam_event,
                                                                          this, NULL, NULL);
        lib->scheduler->schedule_job_ms(lib->scheduler, job, ROAM_DELAY);
}

/**
 * check if an interface with a given index is up and usable
 *
 * this->lock must be locked when calling this function
 */
static bool is_interface_up_and_usable(private_kernel_netlink_net_t *this,
                                                                           int index)
{
        iface_entry_t *iface;

        if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
                                                                 (void**)&iface, index))
        {
                return iface_entry_up_and_usable(iface);
        }
        return FALSE;
}

/**
 * unregister the current addr_entry_t from the hashtable it is stored in
 *
 * this->lock must be locked when calling this function
 */
CALLBACK(addr_entry_unregister, void,
        addr_entry_t *addr, va_list args)
{
        private_kernel_netlink_net_t *this;
        iface_entry_t *iface;

        VA_ARGS_VGET(args, iface, this);
        if (addr->refcount)
        {
                addr_map_entry_remove(this->vips, addr, iface);
                this->condvar->broadcast(this->condvar);
                return;
        }
        addr_map_entry_remove(this->addrs, addr, iface);
}

/**
 * process RTM_NEWLINK/RTM_DELLINK from kernel
 */
static void process_link(private_kernel_netlink_net_t *this,
                                                 struct nlmsghdr *hdr, bool event)
{
        struct ifinfomsg* msg = NLMSG_DATA(hdr);
        struct rtattr *rta = IFLA_RTA(msg);
        size_t rtasize = IFLA_PAYLOAD (hdr);
        enumerator_t *enumerator;
        iface_entry_t *current, *entry = NULL;
        char *name = NULL;
        bool update = FALSE, update_routes = FALSE;

        while (RTA_OK(rta, rtasize))
        {
                switch (rta->rta_type)
                {
                        case IFLA_IFNAME:
                                name = RTA_DATA(rta);
                                break;
                }
                rta = RTA_NEXT(rta, rtasize);
        }
        if (!name)
        {
                name = "(unknown)";
        }

        this->lock->write_lock(this->lock);
        switch (hdr->nlmsg_type)
        {
                case RTM_NEWLINK:
                {
                        if (!this->ifaces->find_first(this->ifaces, iface_entry_by_index,
                                                                                 (void**)&entry, msg->ifi_index))
                        {
                                INIT(entry,
                                        .ifindex = msg->ifi_index,
                                        .addrs = linked_list_create(),
                                );
                                this->ifaces->insert_last(this->ifaces, entry);
                        }
                        strncpy(entry->ifname, name, IFNAMSIZ);
                        entry->ifname[IFNAMSIZ-1] = '\0';
                        entry->usable = charon->kernel->is_interface_usable(charon->kernel,
                                                                                                                                name);
                        if (event && entry->usable)
                        {
                                if (!(entry->flags & IFF_UP) && (msg->ifi_flags & IFF_UP))
                                {
                                        update = update_routes = TRUE;
                                        DBG1(DBG_KNL, "interface %s activated", name);
                                }
                                if ((entry->flags & IFF_UP) && !(msg->ifi_flags & IFF_UP))
                                {
                                        update = TRUE;
                                        DBG1(DBG_KNL, "interface %s deactivated", name);
                                }
                        }
                        entry->flags = msg->ifi_flags;
                        break;
                }
                case RTM_DELLINK:
                {
                        enumerator = this->ifaces->create_enumerator(this->ifaces);
                        while (enumerator->enumerate(enumerator, &current))
                        {
                                if (current->ifindex == msg->ifi_index)
                                {
                                        if (event && current->usable)
                                        {
                                                update = TRUE;
                                                DBG1(DBG_KNL, "interface %s deleted", current->ifname);
                                        }
                                        /* TODO: move virtual IPs installed on this interface to
                                         * another interface? */
                                        this->ifaces->remove_at(this->ifaces, enumerator);
                                        current->addrs->invoke_function(current->addrs,
                                                                                addr_entry_unregister, current, this);
                                        iface_entry_destroy(current);
                                        break;
                                }
                        }
                        enumerator->destroy(enumerator);
                        break;
                }
        }
        this->lock->unlock(this->lock);

        if (update_routes && event)
        {
                queue_route_reinstall(this, strdup(name));
        }

        if (update && event)
        {
                fire_roam_event(this, TRUE);
        }
}

/**
 * process RTM_NEWADDR/RTM_DELADDR from kernel
 */
static void process_addr(private_kernel_netlink_net_t *this,
                                                 struct nlmsghdr *hdr, bool event)
{
        struct ifaddrmsg* msg = NLMSG_DATA(hdr);
        struct rtattr *rta = IFA_RTA(msg);
        size_t rtasize = IFA_PAYLOAD (hdr);
        host_t *host = NULL;
        iface_entry_t *iface;
        chunk_t local = chunk_empty, address = chunk_empty;
        char *route_ifname = NULL;
        bool update = FALSE, found = FALSE, changed = FALSE;

        while (RTA_OK(rta, rtasize))
        {
                switch (rta->rta_type)
                {
                        case IFA_LOCAL:
                                local.ptr = RTA_DATA(rta);
                                local.len = RTA_PAYLOAD(rta);
                                break;
                        case IFA_ADDRESS:
                                address.ptr = RTA_DATA(rta);
                                address.len = RTA_PAYLOAD(rta);
                                break;
                }
                rta = RTA_NEXT(rta, rtasize);
        }

        /* For PPP interfaces, we need the IFA_LOCAL address,
         * IFA_ADDRESS is the peers address. But IFA_LOCAL is
         * not included in all cases (IPv6?), so fallback to IFA_ADDRESS. */
        if (local.ptr)
        {
                host = host_create_from_chunk(msg->ifa_family, local, 0);
        }
        else if (address.ptr)
        {
                host = host_create_from_chunk(msg->ifa_family, address, 0);
        }

        if (host == NULL)
        {       /* bad family? */
                return;
        }

        this->lock->write_lock(this->lock);
        if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
                                                                 (void**)&iface, msg->ifa_index))
        {
                addr_map_entry_t *entry, lookup = {
                        .ip = host,
                        .iface = iface,
                };
                addr_entry_t *addr;

                entry = this->vips->get(this->vips, &lookup);
                if (entry)
                {
                        if (hdr->nlmsg_type == RTM_NEWADDR)
                        {       /* mark as installed and signal waiting threads */
                                entry->addr->installed = TRUE;
                        }
                        else
                        {       /* the address was already marked as uninstalled */
                                addr = entry->addr;
                                iface->addrs->remove(iface->addrs, addr, NULL);
                                addr_map_entry_remove(this->vips, addr, iface);
                                addr_entry_destroy(addr);
                        }
                        /* no roam events etc. for virtual IPs */
                        this->condvar->broadcast(this->condvar);
                        this->lock->unlock(this->lock);
                        host->destroy(host);
                        return;
                }
                entry = this->addrs->get(this->addrs, &lookup);
                if (entry)
                {
                        if (hdr->nlmsg_type == RTM_DELADDR)
                        {
                                found = TRUE;
                                addr = entry->addr;
                                iface->addrs->remove(iface->addrs, addr, NULL);
                                if (iface->usable)
                                {
                                        changed = TRUE;
                                        DBG1(DBG_KNL, "%H disappeared from %s", host,
                                                 iface->ifname);
                                }
                                addr_map_entry_remove(this->addrs, addr, iface);
                                addr_entry_destroy(addr);
                        }
                }
                else
                {
                        if (hdr->nlmsg_type == RTM_NEWADDR)
                        {
                                found = TRUE;
                                changed = TRUE;
                                route_ifname = strdup(iface->ifname);
                                INIT(addr,
                                        .ip = host->clone(host),
                                        .flags = msg->ifa_flags,
                                        .scope = msg->ifa_scope,
                                );
                                iface->addrs->insert_last(iface->addrs, addr);
                                addr_map_entry_add(this->addrs, addr, iface);
                                if (event && iface->usable)
                                {
                                        DBG1(DBG_KNL, "%H appeared on %s", host, iface->ifname);
                                }
                        }
                }
                if (found && (iface->flags & IFF_UP))
                {
                        update = TRUE;
                }
                if (!iface->usable)
                {       /* ignore events for interfaces excluded by config */
                        update = changed = FALSE;
                }
        }
        this->lock->unlock(this->lock);

        if (update && event && route_ifname)
        {
                queue_route_reinstall(this, route_ifname);
        }
        else
        {
                free(route_ifname);
        }
        host->destroy(host);

        /* send an update to all IKE_SAs */
        if (update && event && changed)
        {
                fire_roam_event(this, TRUE);
        }
}

/**
 * process RTM_NEWROUTE and RTM_DELROUTE from kernel
 */
static void process_route(private_kernel_netlink_net_t *this,
                                                  struct nlmsghdr *hdr)
{
        struct rtmsg* msg = NLMSG_DATA(hdr);
        struct rtattr *rta = RTM_RTA(msg);
        size_t rtasize = RTM_PAYLOAD(hdr);
        uint32_t rta_oif = 0;
        host_t *host = NULL;

        /* ignore routes added by us or in the local routing table (local addrs) */
        if (msg->rtm_table && (msg->rtm_table == this->routing_table ||
                                                   msg->rtm_table == RT_TABLE_LOCAL))
        {
                return;
        }
        else if (msg->rtm_flags & RTM_F_CLONED)
        {       /* ignore cached routes, seem to be created a lot for IPv6 */
                return;
        }

        while (RTA_OK(rta, rtasize))
        {
                switch (rta->rta_type)
                {
#ifdef HAVE_RTA_TABLE
                        case RTA_TABLE:
                                /* also check against extended table ID */
                                if (RTA_PAYLOAD(rta) == sizeof(uint32_t) &&
                                        this->routing_table == *(uint32_t*)RTA_DATA(rta))
                                {
                                        return;
                                }
                                break;
#endif /* HAVE_RTA_TABLE */
                        case RTA_PREFSRC:
                                DESTROY_IF(host);
                                host = host_create_from_chunk(msg->rtm_family,
                                                        chunk_create(RTA_DATA(rta), RTA_PAYLOAD(rta)), 0);
                                break;
                        case RTA_OIF:
                                if (RTA_PAYLOAD(rta) == sizeof(rta_oif))
                                {
                                        rta_oif = *(uint32_t*)RTA_DATA(rta);
                                }
                                break;
                }
                rta = RTA_NEXT(rta, rtasize);
        }
        this->lock->read_lock(this->lock);
        if (rta_oif && !is_interface_up_and_usable(this, rta_oif))
        {       /* ignore route changes for interfaces that are ignored or down */
                this->lock->unlock(this->lock);
                DESTROY_IF(host);
                return;
        }
        if (!host && rta_oif)
        {
                host = get_interface_address(this, rta_oif, msg->rtm_family,
                                                                         NULL, NULL);
        }
        if (!host || is_known_vip(this, host))
        {       /* ignore routes added for virtual IPs */
                this->lock->unlock(this->lock);
                DESTROY_IF(host);
                return;
        }
        this->lock->unlock(this->lock);
        fire_roam_event(this, FALSE);
        host->destroy(host);
}

/**
 * process RTM_NEW|DELRULE from kernel
 */
static void process_rule(private_kernel_netlink_net_t *this,
                                                 struct nlmsghdr *hdr)
{
#ifdef HAVE_LINUX_FIB_RULES_H
        struct rtmsg* msg = NLMSG_DATA(hdr);
        struct rtattr *rta = RTM_RTA(msg);
        size_t rtasize = RTM_PAYLOAD(hdr);

        /* ignore rules added by us or in the local routing table (local addrs) */
        if (msg->rtm_table && (msg->rtm_table == this->routing_table ||
                                                   msg->rtm_table == RT_TABLE_LOCAL))
        {
                return;
        }

        while (RTA_OK(rta, rtasize))
        {
                switch (rta->rta_type)
                {
                        case FRA_TABLE:
                                /* also check against extended table ID */
                                if (RTA_PAYLOAD(rta) == sizeof(uint32_t) &&
                                        this->routing_table == *(uint32_t*)RTA_DATA(rta))
                                {
                                        return;
                                }
                                break;
                }
                rta = RTA_NEXT(rta, rtasize);
        }
        fire_roam_event(this, FALSE);
#endif
}

/**
 * Receives events from kernel
 */
static bool receive_events(private_kernel_netlink_net_t *this, int fd,
                                                   watcher_event_t event)
{
        char response[netlink_get_buflen()];
        struct nlmsghdr *hdr = (struct nlmsghdr*)response;
        struct sockaddr_nl addr;
        socklen_t addr_len = sizeof(addr);
        int len;

        len = recvfrom(this->socket_events, response, sizeof(response),
                                   MSG_DONTWAIT, (struct sockaddr*)&addr, &addr_len);
        if (len < 0)
        {
                switch (errno)
                {
                        case EINTR:
                                /* interrupted, try again */
                                return TRUE;
                        case EAGAIN:
                                /* no data ready, select again */
                                return TRUE;
                        default:
                                DBG1(DBG_KNL, "unable to receive from RT event socket %s (%d)",
                                         strerror(errno), errno);
                                sleep(1);
                                return TRUE;
                }
        }

        if (addr.nl_pid != 0)
        {       /* not from kernel. not interested, try another one */
                return TRUE;
        }

        while (NLMSG_OK(hdr, len))
        {
                /* looks good so far, dispatch netlink message */
                switch (hdr->nlmsg_type)
                {
                        case RTM_NEWADDR:
                        case RTM_DELADDR:
                                process_addr(this, hdr, TRUE);
                                break;
                        case RTM_NEWLINK:
                        case RTM_DELLINK:
                                process_link(this, hdr, TRUE);
                                break;
                        case RTM_NEWROUTE:
                        case RTM_DELROUTE:
                                if (this->process_route)
                                {
                                        process_route(this, hdr);
                                }
                                break;
                        case RTM_NEWRULE:
                        case RTM_DELRULE:
                                if (this->process_rules)
                                {
                                        process_rule(this, hdr);
                                }
                                break;
                        default:
                                break;
                }
                hdr = NLMSG_NEXT(hdr, len);
        }
        return TRUE;
}

/** enumerator over addresses */
typedef struct {
        private_kernel_netlink_net_t* this;
        /** which addresses to enumerate */
        kernel_address_type_t which;
} address_enumerator_t;

CALLBACK(address_enumerator_destroy, void,
        address_enumerator_t *data)
{
        data->this->lock->unlock(data->this->lock);
        free(data);
}

CALLBACK(filter_addresses, bool,
        address_enumerator_t *data, enumerator_t *orig, va_list args)
{
        addr_entry_t *addr;
        host_t **out;

        VA_ARGS_VGET(args, out);

        while (orig->enumerate(orig, &addr))
        {
                if (!(data->which & ADDR_TYPE_VIRTUAL) && addr->refcount)
                {       /* skip virtual interfaces added by us */
                        continue;
                }
                if (!(data->which & ADDR_TYPE_REGULAR) && !addr->refcount)
                {       /* address is regular, but not requested */
                        continue;
                }
                if (addr->flags & IFA_F_DEPRECATED ||
                        addr->scope >= RT_SCOPE_LINK)
                {       /* skip deprecated addresses or those with an unusable scope */
                        continue;
                }
                if (addr->ip->get_family(addr->ip) == AF_INET6)
                {       /* handle temporary IPv6 addresses according to config */
                        bool temporary = (addr->flags & IFA_F_TEMPORARY) == IFA_F_TEMPORARY;
                        if (data->this->prefer_temporary_addrs != temporary)
                        {
                                continue;
                        }
                }
                *out = addr->ip;
                return TRUE;
        }
        return FALSE;
}

/**
 * enumerator constructor for interfaces
 */
static enumerator_t *create_iface_enumerator(iface_entry_t *iface,
                                                                                         address_enumerator_t *data)
{
        return enumerator_create_filter(
                                                iface->addrs->create_enumerator(iface->addrs),
                                                filter_addresses, data, NULL);
}

CALLBACK(filter_interfaces, bool,
        address_enumerator_t *data, enumerator_t *orig, va_list args)
{
        iface_entry_t *iface, **out;

        VA_ARGS_VGET(args, out);

        while (orig->enumerate(orig, &iface))
        {
                if (!(data->which & ADDR_TYPE_IGNORED) && !iface->usable)
                {       /* skip interfaces excluded by config */
                        continue;
                }
                if (!(data->which & ADDR_TYPE_LOOPBACK) && (iface->flags & IFF_LOOPBACK))
                {       /* ignore loopback devices */
                        continue;
                }
                if (!(data->which & ADDR_TYPE_DOWN) && !(iface->flags & IFF_UP))
                {       /* skip interfaces not up */
                        continue;
                }
                *out = iface;
                return TRUE;
        }
        return FALSE;
}

METHOD(kernel_net_t, create_address_enumerator, enumerator_t*,
        private_kernel_netlink_net_t *this, kernel_address_type_t which)
{
        address_enumerator_t *data;

        INIT(data,
                .this = this,
                .which = which,
        );

        this->lock->read_lock(this->lock);
        return enumerator_create_nested(
                                enumerator_create_filter(
                                        this->ifaces->create_enumerator(this->ifaces),
                                        filter_interfaces, data, NULL),
                                (void*)create_iface_enumerator, data,
                                address_enumerator_destroy);
}

METHOD(kernel_net_t, get_interface_name, bool,
        private_kernel_netlink_net_t *this, host_t* ip, char **name)
{
        addr_map_entry_t *entry, lookup = {
                .ip = ip,
        };

        if (ip->is_anyaddr(ip))
        {
                return FALSE;
        }
        this->lock->read_lock(this->lock);
        /* first try to find it on an up and usable interface */
        entry = this->addrs->get_match(this->addrs, &lookup,
                                                                  (void*)addr_map_entry_match_up_and_usable);
        if (entry)
        {
                if (name)
                {
                        *name = strdup(entry->iface->ifname);
                        DBG2(DBG_KNL, "%H is on interface %s", ip, *name);
                }
                this->lock->unlock(this->lock);
                return TRUE;
        }
        /* in a second step, consider virtual IPs installed by us */
        entry = this->vips->get_match(this->vips, &lookup,
                                                                  (void*)addr_map_entry_match_up_and_usable);
        if (entry)
        {
                if (name)
                {
                        *name = strdup(entry->iface->ifname);
                        DBG2(DBG_KNL, "virtual IP %H is on interface %s", ip, *name);
                }
                this->lock->unlock(this->lock);
                return TRUE;
        }
        /* maybe it is installed on an ignored interface */
        entry = this->addrs->get_match(this->addrs, &lookup,
                                                                  (void*)addr_map_entry_match_up);
        if (!entry)
        {
                DBG2(DBG_KNL, "%H is not a local address or the interface is down", ip);
        }
        this->lock->unlock(this->lock);
        return FALSE;
}

/**
 * get the index of an interface by name
 */
static int get_interface_index(private_kernel_netlink_net_t *this, char* name)
{
        iface_entry_t *iface;
        int ifindex = 0;

        DBG2(DBG_KNL, "getting iface index for %s", name);

        this->lock->read_lock(this->lock);
        if (this->ifaces->find_first(this->ifaces, iface_entry_by_name,
                                                                (void**)&iface, name))
        {
                ifindex = iface->ifindex;
        }
        this->lock->unlock(this->lock);

        if (ifindex == 0)
        {
                DBG1(DBG_KNL, "unable to get interface index for %s", name);
        }
        return ifindex;
}

/**
 * get the name of an interface by index (allocated)
 */
static char *get_interface_name_by_index(private_kernel_netlink_net_t *this,
                                                                                 int index)
{
        iface_entry_t *iface;
        char *name = NULL;

        DBG2(DBG_KNL, "getting iface name for index %d", index);

        this->lock->read_lock(this->lock);
        if (this->ifaces->find_first(this->ifaces, iface_entry_by_index,
                                                                (void**)&iface, index))
        {
                name = strdup(iface->ifname);
        }
        this->lock->unlock(this->lock);

        if (!name)
        {
                DBG1(DBG_KNL, "unable to get interface name for %d", index);
        }
        return name;
}

/**
 * Store information about a route retrieved via RTNETLINK
 */
typedef struct {
        chunk_t gtw;
        chunk_t pref_src;
        chunk_t dst;
        chunk_t src;
        host_t *src_host;
        uint8_t dst_len;
        uint8_t src_len;
        uint32_t table;
        uint32_t oif;
        uint32_t priority;
} rt_entry_t;

/**
 * Free a route entry
 */
static void rt_entry_destroy(rt_entry_t *this)
{
        DESTROY_IF(this->src_host);
        free(this);
}

/**
 * Check if the route received with RTM_NEWROUTE is usable based on its type.
 */
static bool route_usable(struct nlmsghdr *hdr, bool allow_local)
{
        struct rtmsg *msg;

        msg = NLMSG_DATA(hdr);
        switch (msg->rtm_type)
        {
                case RTN_BLACKHOLE:
                case RTN_UNREACHABLE:
                case RTN_PROHIBIT:
                case RTN_THROW:
                        return FALSE;
                case RTN_LOCAL:
                        return allow_local;
                default:
                        return TRUE;
        }
}

/**
 * Parse route received with RTM_NEWROUTE. The given rt_entry_t object will be
 * reused if not NULL.
 *
 * Returned chunks point to internal data of the Netlink message.
 */
static rt_entry_t *parse_route(struct nlmsghdr *hdr, rt_entry_t *route)
{
        struct rtattr *rta;
        struct rtmsg *msg;
        size_t rtasize;

        msg = NLMSG_DATA(hdr);
        rta = RTM_RTA(msg);
        rtasize = RTM_PAYLOAD(hdr);

        if (route)
        {
                *route = (rt_entry_t){
                        .dst_len = msg->rtm_dst_len,
                        .src_len = msg->rtm_src_len,
                        .table = msg->rtm_table,
                };
        }
        else
        {
                INIT(route,
                        .dst_len = msg->rtm_dst_len,
                        .src_len = msg->rtm_src_len,
                        .table = msg->rtm_table,
                );
        }

        while (RTA_OK(rta, rtasize))
        {
                switch (rta->rta_type)
                {
                        case RTA_PREFSRC:
                                route->pref_src = chunk_create(RTA_DATA(rta), RTA_PAYLOAD(rta));
                                break;
                        case RTA_GATEWAY:
                                route->gtw = chunk_create(RTA_DATA(rta), RTA_PAYLOAD(rta));
                                break;
                        case RTA_DST:
                                route->dst = chunk_create(RTA_DATA(rta), RTA_PAYLOAD(rta));
                                break;
                        case RTA_SRC:
                                route->src = chunk_create(RTA_DATA(rta), RTA_PAYLOAD(rta));
                                break;
                        case RTA_OIF:
                                if (RTA_PAYLOAD(rta) == sizeof(route->oif))
                                {
                                        route->oif = *(uint32_t*)RTA_DATA(rta);
                                }
                                break;
                        case RTA_PRIORITY:
                                if (RTA_PAYLOAD(rta) == sizeof(route->priority))
                                {
                                        route->priority = *(uint32_t*)RTA_DATA(rta);
                                }
                                break;
#ifdef HAVE_RTA_TABLE
                        case RTA_TABLE:
                                if (RTA_PAYLOAD(rta) == sizeof(route->table))
                                {
                                        route->table = *(uint32_t*)RTA_DATA(rta);
                                }
                                break;
#endif /* HAVE_RTA_TABLE*/
                }
                rta = RTA_NEXT(rta, rtasize);
        }
        return route;
}

/**
 * Get a route: If "nexthop", the nexthop is returned. source addr otherwise.
 */
static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
                                                 int prefix, bool nexthop, host_t *candidate,
                                                 char **iface, u_int recursion)
{
        netlink_buf_t request;
        struct nlmsghdr *hdr, *out, *current;
        struct rtmsg *msg;
        chunk_t chunk;
        size_t len;
        linked_list_t *routes;
        rt_entry_t *route = NULL, *best = NULL;
        enumerator_t *enumerator;
        host_t *addr = NULL;
        bool match_net;
        int family;

        if (recursion > MAX_ROUTE_RECURSION)
        {
                return NULL;
        }
        chunk = dest->get_address(dest);
        len = chunk.len * 8;
        prefix = prefix < 0 ? len : min(prefix, len);
        match_net = prefix != len;

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

        family = dest->get_family(dest);
        hdr = &request.hdr;
        hdr->nlmsg_flags = NLM_F_REQUEST;
        hdr->nlmsg_type = RTM_GETROUTE;
        hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));

        msg = NLMSG_DATA(hdr);
        msg->rtm_family = family;
        if (!match_net && this->rta_mark && this->routing_mark.value)
        {
                /* if our routing rule excludes packets with a certain mark we can
                 * get the preferred route without having to dump all routes */
                chunk = chunk_from_thing(this->routing_mark.value);
                netlink_add_attribute(hdr, RTA_MARK, chunk, sizeof(request));
        }
        else if (family == AF_INET || this->rta_prefsrc_for_ipv6 ||
                         this->routing_table || match_net)
        {       /* kernels prior to 3.0 do not support RTA_PREFSRC for IPv6 routes.
                 * as we want to ignore routes with virtual IPs we cannot use DUMP
                 * if these routes are not installed in a separate table */
                if (this->install_routes)
                {
                        hdr->nlmsg_flags |= NLM_F_DUMP;
                }
        }
        if (candidate)
        {
                chunk = candidate->get_address(candidate);
                if (hdr->nlmsg_flags & NLM_F_DUMP)
                {
                        netlink_add_attribute(hdr, RTA_PREFSRC, chunk, sizeof(request));
                }
                else
                {
                        netlink_add_attribute(hdr, RTA_SRC, chunk, sizeof(request));
                }
        }
        /* we use this below to match against the routes */
        chunk = dest->get_address(dest);
        if (!match_net)
        {
                netlink_add_attribute(hdr, RTA_DST, chunk, sizeof(request));
        }

        if (this->socket->send(this->socket, hdr, &out, &len) != SUCCESS)
        {
                DBG2(DBG_KNL, "getting %s to reach %H/%d failed",
                         nexthop ? "nexthop" : "address", dest, prefix);
                return NULL;
        }
        routes = linked_list_create();
        this->lock->read_lock(this->lock);

        for (current = out; NLMSG_OK(current, len);
                 current = NLMSG_NEXT(current, len))
        {
                switch (current->nlmsg_type)
                {
                        case NLMSG_DONE:
                                break;
                        case RTM_NEWROUTE:
                        {
                                rt_entry_t *other;
                                uintptr_t table;

                                if (!route_usable(current, TRUE))
                                {
                                        continue;
                                }
                                route = parse_route(current, route);

                                table = (uintptr_t)route->table;
                                if (this->rt_exclude->find_first(this->rt_exclude, NULL,
                                                                                                 (void**)&table))
                                {       /* route is from an excluded routing table */
                                        continue;
                                }
                                if (this->routing_table != 0 &&
                                        route->table == this->routing_table)
                                {       /* route is from our own ipsec routing table */
                                        continue;
                                }
                                if (route->oif && !is_interface_up_and_usable(this, route->oif))
                                {       /* interface is down */
                                        continue;
                                }
                                if (!addr_in_subnet(chunk, prefix, route->dst, route->dst_len))
                                {       /* route destination does not contain dest */
                                        continue;
                                }
                                if (route->pref_src.ptr)
                                {       /* verify source address, if any */
                                        host_t *src = host_create_from_chunk(msg->rtm_family,
                                                                                                                 route->pref_src, 0);
                                        if (src && is_known_vip(this, src))
                                        {       /* ignore routes installed by us */
                                                src->destroy(src);
                                                continue;
                                        }
                                        route->src_host = src;
                                }
                                /* insert route, sorted by network prefix and priority */
                                enumerator = routes->create_enumerator(routes);
                                while (enumerator->enumerate(enumerator, &other))
                                {
                                        if (route->dst_len > other->dst_len)
                                        {
                                                break;
                                        }
                                        if (route->dst_len == other->dst_len &&
                                                route->priority < other->priority)
                                        {
                                                break;
                                        }
                                }
                                routes->insert_before(routes, enumerator, route);
                                enumerator->destroy(enumerator);
                                route = NULL;
                                continue;
                        }
                        default:
                                continue;
                }
                break;
        }
        if (route)
        {
                rt_entry_destroy(route);
        }

        /* now we have a list of routes matching dest, sorted by net prefix.
         * we will look for source addresses for these routes and select the one
         * with the preferred source address, if possible */
        enumerator = routes->create_enumerator(routes);
        while (enumerator->enumerate(enumerator, &route))
        {
                if (route->src_host)
                {       /* got a source address with the route, if no preferred source
                         * is given or it matches we are done, as this is the best route */
                        if (!candidate || candidate->ip_equals(candidate, route->src_host))
                        {
                                best = route;
                                break;
                        }
                        else if (route->oif)
                        {       /* no match yet, maybe it is assigned to the same interface */
                                host_t *src = get_interface_address(this, route->oif,
                                                                                        msg->rtm_family, dest, candidate);
                                if (src && src->ip_equals(src, candidate))
                                {
                                        route->src_host->destroy(route->src_host);
                                        route->src_host = src;
                                        best = route;
                                        break;
                                }
                                DESTROY_IF(src);
                        }
                        /* no luck yet with the source address. if this is the best (first)
                         * route we store it as fallback in case we don't find a route with
                         * the preferred source */
                        best = best ?: route;
                        continue;
                }
                if (route->src.ptr)
                {       /* no src, but a source selector, try to find a matching address */
                        route->src_host = get_subnet_address(this, msg->rtm_family,
                                                                                        route->src, route->src_len, dest,
                                                                                        candidate);
                        if (route->src_host)
                        {       /* we handle this address the same as the one above */
                                if (!candidate ||
                                         candidate->ip_equals(candidate, route->src_host))
                                {
                                        best = route;
                                        break;
                                }
                                best = best ?: route;
                                continue;
                        }
                }
                if (route->oif)
                {       /* no src, but an interface - get address from it */
                        route->src_host = get_interface_address(this, route->oif,
                                                                                        msg->rtm_family, dest, candidate);
                        if (route->src_host)
                        {       /* more of the same */
                                if (!candidate ||
                                         candidate->ip_equals(candidate, route->src_host))
                                {
                                        best = route;
                                        break;
                                }
                                best = best ?: route;
                                continue;
                        }
                }
                if (route->gtw.ptr)
                {       /* no src, no iface, but a gateway - lookup src to reach gtw */
                        host_t *gtw;

                        gtw = host_create_from_chunk(msg->rtm_family, route->gtw, 0);
                        if (gtw && !gtw->ip_equals(gtw, dest))
                        {
                                route->src_host = get_route(this, gtw, -1, FALSE, candidate,
                                                                                        iface, recursion + 1);
                        }
                        DESTROY_IF(gtw);
                        if (route->src_host)
                        {       /* more of the same */
                                if (!candidate ||
                                         candidate->ip_equals(candidate, route->src_host))
                                {
                                        best = route;
                                        break;
                                }
                                best = best ?: route;
                        }
                }
        }
        enumerator->destroy(enumerator);

        if (nexthop)
        {       /* nexthop lookup, return gateway and oif if any */
                if (iface)
                {
                        *iface = NULL;
                }
                if (best || routes->get_first(routes, (void**)&best) == SUCCESS)
                {
                        addr = host_create_from_chunk(msg->rtm_family, best->gtw, 0);
                        if (iface && best->oif)
                        {
                                *iface = get_interface_name_by_index(this, best->oif);
                        }
                }
                if (!addr && !match_net)
                {       /* fallback to destination address */
                        addr = dest->clone(dest);
                }
        }
        else
        {
                if (best)
                {
                        addr = best->src_host->clone(best->src_host);
                }
        }
        this->lock->unlock(this->lock);
        routes->destroy_function(routes, (void*)rt_entry_destroy);
        free(out);

        if (addr)
        {
                if (nexthop && iface && *iface)
                {
                        DBG2(DBG_KNL, "using %H as nexthop and %s as dev to reach %H/%d",
                                 addr, *iface, dest, prefix);
                }
                else
                {
                        DBG2(DBG_KNL, "using %H as %s to reach %H/%d", addr,
                                 nexthop ? "nexthop" : "address", dest, prefix);
                }
        }
        else if (!recursion)
        {
                DBG2(DBG_KNL, "no %s found to reach %H/%d",
                         nexthop ? "nexthop" : "address", dest, prefix);
        }
        return addr;
}

METHOD(kernel_net_t, get_source_addr, host_t*,
        private_kernel_netlink_net_t *this, host_t *dest, host_t *src)
{
        return get_route(this, dest, -1, FALSE, src, NULL, 0);
}

METHOD(kernel_net_t, get_nexthop, host_t*,
        private_kernel_netlink_net_t *this, host_t *dest, int prefix, host_t *src,
        char **iface)
{
        return get_route(this, dest, prefix, TRUE, src, iface, 0);
}

/** enumerator over subnets */
typedef struct {
        enumerator_t public;
        private_kernel_netlink_net_t *private;
        /** message from the kernel */
        struct nlmsghdr *msg;
        /** current message from the kernel */
        struct nlmsghdr *current;
        /** remaining length */
        size_t len;
        /** last subnet enumerated */
        host_t *net;
        /** interface of current net */
        char ifname[IFNAMSIZ];
} subnet_enumerator_t;

METHOD(enumerator_t, destroy_subnet_enumerator, void,
        subnet_enumerator_t *this)
{
        DESTROY_IF(this->net);
        free(this->msg);
        free(this);
}

METHOD(enumerator_t, enumerate_subnets, bool,
        subnet_enumerator_t *this, va_list args)
{
        host_t **net;
        uint8_t *mask;
        char **ifname;

        VA_ARGS_VGET(args, net, mask, ifname);

        if (!this->current)
        {
                this->current = this->msg;
        }
        else
        {
                this->current = NLMSG_NEXT(this->current, this->len);
                DESTROY_IF(this->net);
                this->net = NULL;
        }

        while (NLMSG_OK(this->current, this->len))
        {
                switch (this->current->nlmsg_type)
                {
                        case NLMSG_DONE:
                                break;
                        case RTM_NEWROUTE:
                        {
                                rt_entry_t route;

                                if (!route_usable(this->current, FALSE))
                                {
                                        break;
                                }
                                parse_route(this->current, &route);

                                if (route.table && (
                                                        route.table == RT_TABLE_LOCAL ||
                                                        route.table == this->private->routing_table))
                                {       /* ignore our own and the local routing tables */
                                        break;
                                }
                                else if (route.gtw.ptr)
                                {       /* ignore routes via gateway/next hop */
                                        break;
                                }

                                if (route.dst.ptr && route.oif &&
                                        if_indextoname(route.oif, this->ifname))
                                {
                                        this->net = host_create_from_chunk(AF_UNSPEC, route.dst, 0);
                                        *net = this->net;
                                        *mask = route.dst_len;
                                        *ifname = this->ifname;
                                        return TRUE;
                                }
                                break;
                        }
                        default:
                                break;
                }
                this->current = NLMSG_NEXT(this->current, this->len);
        }
        return FALSE;
}

METHOD(kernel_net_t, create_local_subnet_enumerator, enumerator_t*,
        private_kernel_netlink_net_t *this)
{
        netlink_buf_t request;
        struct nlmsghdr *hdr, *out;
        struct rtmsg *msg;
        size_t len;
        subnet_enumerator_t *enumerator;

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

        hdr = &request.hdr;
        hdr->nlmsg_flags = NLM_F_REQUEST;
        hdr->nlmsg_type = RTM_GETROUTE;
        hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
        hdr->nlmsg_flags |= NLM_F_DUMP;

        msg = NLMSG_DATA(hdr);
        msg->rtm_scope = RT_SCOPE_LINK;

        if (this->socket->send(this->socket, hdr, &out, &len) != SUCCESS)
        {
                DBG2(DBG_KNL, "enumerating local subnets failed");
                return enumerator_create_empty();
        }

        INIT(enumerator,
                .public = {
                        .enumerate = enumerator_enumerate_default,
                        .venumerate = _enumerate_subnets,
                        .destroy = _destroy_subnet_enumerator,
                },
                .private = this,
                .msg = out,
                .len = len,
        );
        return &enumerator->public;
}

/**
 * Manages the creation and deletion of IPv6 address labels for virtual IPs.
 * By setting the appropriate nlmsg_type the label is either added or removed.
 */
static status_t manage_addrlabel(private_kernel_netlink_net_t *this,
                                                                 int nlmsg_type, host_t *ip)
{
        netlink_buf_t request;
        struct nlmsghdr *hdr;
        struct ifaddrlblmsg *msg;
        chunk_t chunk;
        uint32_t label;

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

        chunk = ip->get_address(ip);

        hdr = &request.hdr;
        hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
        if (nlmsg_type == RTM_NEWADDRLABEL)
        {
                hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_EXCL;
        }
        hdr->nlmsg_type = nlmsg_type;
        hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrlblmsg));

        msg = NLMSG_DATA(hdr);
        msg->ifal_family = ip->get_family(ip);
        msg->ifal_prefixlen = chunk.len * 8;

        netlink_add_attribute(hdr, IFAL_ADDRESS, chunk, sizeof(request));
        /* doesn't really matter as default labels are < 20 but this makes it kinda
         * recognizable */
        label = 220;
        netlink_add_attribute(hdr, IFAL_LABEL, chunk_from_thing(label),
                                                  sizeof(request));

        return this->socket->send_ack(this->socket, hdr);
}

/**
 * Manages the creation and deletion of ip addresses on an interface.
 * By setting the appropriate nlmsg_type, the ip will be set or unset.
 */
static status_t manage_ipaddr(private_kernel_netlink_net_t *this, int nlmsg_type,
                                                          int flags, int if_index, host_t *ip, int prefix)
{
        netlink_buf_t request;
        struct nlmsghdr *hdr;
        struct ifaddrmsg *msg;
        chunk_t chunk;

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

        chunk = ip->get_address(ip);

        hdr = &request.hdr;
        hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
        hdr->nlmsg_type = nlmsg_type;
        hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));

        msg = NLMSG_DATA(hdr);
        msg->ifa_family = ip->get_family(ip);
        msg->ifa_flags = 0;
        msg->ifa_prefixlen = prefix < 0 ? chunk.len * 8 : prefix;
        msg->ifa_scope = RT_SCOPE_UNIVERSE;
        msg->ifa_index = if_index;

        netlink_add_attribute(hdr, IFA_LOCAL, chunk, sizeof(request));

        if (ip->get_family(ip) == AF_INET6)
        {
#ifdef IFA_F_NODAD
                msg->ifa_flags |= IFA_F_NODAD;
#endif
                if (this->rta_prefsrc_for_ipv6)
                {
                        /* if source routes are possible we set a label for this virtual IP
                         * so it gets only used if forced by our route, and not by the
                         * default IPv6 address selection */
                        int labelop = nlmsg_type == RTM_NEWADDR ? RTM_NEWADDRLABEL
                                                                                                        : RTM_DELADDRLABEL;
                        if (manage_addrlabel(this, labelop, ip) != SUCCESS)
                        {
                                /* if we can't use address labels we let the virtual IP get
                                 * deprecated immediately (but mark it as valid forever), which
                                 * should also avoid that it gets used by the default address
                                 * selection */
                                struct ifa_cacheinfo cache = {
                                        .ifa_valid = 0xFFFFFFFF,
                                        .ifa_prefered = 0,
                                };
                                netlink_add_attribute(hdr, IFA_CACHEINFO,
                                                                          chunk_from_thing(cache), sizeof(request));
                        }
                }
        }
        return this->socket->send_ack(this->socket, hdr);
}

METHOD(kernel_net_t, add_ip, status_t,
        private_kernel_netlink_net_t *this, host_t *virtual_ip, int prefix,
        char *iface_name)
{
        addr_map_entry_t *entry, lookup = {
                .ip = virtual_ip,
        };
        iface_entry_t *iface = NULL;

        if (!this->install_virtual_ip)
        {       /* disabled by config */
                return SUCCESS;
        }

        this->lock->write_lock(this->lock);
        /* the virtual IP might actually be installed as regular IP, in which case
         * we don't track it as virtual IP */
        entry = this->addrs->get_match(this->addrs, &lookup,
                                                                  (void*)addr_map_entry_match);
        if (!entry)
        {       /* otherwise it might already be installed as virtual IP */
                entry = this->vips->get_match(this->vips, &lookup,
                                                                         (void*)addr_map_entry_match);
                if (entry)
                {       /* the vip we found can be in one of three states: 1) installed and
                         * ready, 2) just added by another thread, but not yet confirmed to
                         * be installed by the kernel, 3) just deleted, but not yet gone.
                         * Then while we wait below, several things could happen (as we
                         * release the lock).  For instance, the interface could disappear,
                         * or the IP is finally deleted, and it reappears on a different
                         * interface. All these cases are handled by the call below. */
                        while (!is_vip_installed_or_gone(this, virtual_ip, &entry))
                        {
                                this->condvar->wait(this->condvar, this->lock);
                        }
                        if (entry)
                        {
                                entry->addr->refcount++;
                        }
                }
        }
        if (entry)
        {
                DBG2(DBG_KNL, "virtual IP %H is already installed on %s", virtual_ip,
                         entry->iface->ifname);
                this->lock->unlock(this->lock);
                return SUCCESS;
        }
        /* try to find the target interface, either by config or via src ip */
        if (!this->install_virtual_ip_on ||
                !this->ifaces->find_first(this->ifaces, iface_entry_by_name,
                                                                 (void**)&iface, this->install_virtual_ip_on))
        {
                if (!this->ifaces->find_first(this->ifaces, iface_entry_by_name,
                                                                         (void**)&iface, iface_name))
                {       /* if we don't find the requested interface we just use the first */
                        this->ifaces->get_first(this->ifaces, (void**)&iface);
                }
        }
        if (iface)
        {
                addr_entry_t *addr;
                char *ifname;
                int ifi;

                INIT(addr,
                        .ip = virtual_ip->clone(virtual_ip),
                        .refcount = 1,
                        .scope = RT_SCOPE_UNIVERSE,
                );
                iface->addrs->insert_last(iface->addrs, addr);
                addr_map_entry_add(this->vips, addr, iface);
                ifi = iface->ifindex;
                this->lock->unlock(this->lock);
                if (manage_ipaddr(this, RTM_NEWADDR, NLM_F_CREATE | NLM_F_EXCL,
                                                  ifi, virtual_ip, prefix) == SUCCESS)
                {
                        this->lock->write_lock(this->lock);
                        while (!is_vip_installed_or_gone(this, virtual_ip, &entry))
                        {       /* wait until address appears */
                                this->condvar->wait(this->condvar, this->lock);
                        }
                        if (entry)
                        {       /* we fail if the interface got deleted in the meantime */
                                ifname = strdup(entry->iface->ifname);
                                this->lock->unlock(this->lock);
                                DBG2(DBG_KNL, "virtual IP %H installed on %s",
                                         virtual_ip, ifname);
                                /* during IKEv1 reauthentication, children get moved from
                                 * old the new SA before the virtual IP is available. This
                                 * kills the route for our virtual IP, reinstall. */
                                queue_route_reinstall(this, ifname);
                                return SUCCESS;
                        }
                        this->lock->unlock(this->lock);
                }
                DBG1(DBG_KNL, "adding virtual IP %H failed", virtual_ip);
                return FAILED;
        }
        this->lock->unlock(this->lock);
        DBG1(DBG_KNL, "no interface available, unable to install virtual IP %H",
                 virtual_ip);
        return FAILED;
}

METHOD(kernel_net_t, del_ip, status_t,
        private_kernel_netlink_net_t *this, host_t *virtual_ip, int prefix,
        bool wait)
{
        addr_map_entry_t *entry, lookup = {
                .ip = virtual_ip,
        };

        if (!this->install_virtual_ip)
        {       /* disabled by config */
                return SUCCESS;
        }

        DBG2(DBG_KNL, "deleting virtual IP %H", virtual_ip);

        this->lock->write_lock(this->lock);
        entry = this->vips->get_match(this->vips, &lookup,
                                                                 (void*)addr_map_entry_match);
        if (!entry)
        {       /* we didn't install this IP as virtual IP */
                entry = this->addrs->get_match(this->addrs, &lookup,
                                                                          (void*)addr_map_entry_match);
                if (entry)
                {
                        DBG2(DBG_KNL, "not deleting existing IP %H on %s", virtual_ip,
                                 entry->iface->ifname);
                        this->lock->unlock(this->lock);
                        return SUCCESS;
                }
                DBG2(DBG_KNL, "virtual IP %H not cached, unable to delete", virtual_ip);
                this->lock->unlock(this->lock);
                return FAILED;
        }
        if (entry->addr->refcount == 1)
        {
                status_t status;
                int ifi;

                /* we set this flag so that threads calling add_ip will block and wait
                 * until the entry is gone, also so we can wait below */
                entry->addr->installed = FALSE;
                ifi = entry->iface->ifindex;
                this->lock->unlock(this->lock);
                status = manage_ipaddr(this, RTM_DELADDR, 0, ifi, virtual_ip, prefix);
                if (status == SUCCESS && wait)
                {       /* wait until the address is really gone */
                        this->lock->write_lock(this->lock);
                        while (is_known_vip(this, virtual_ip))
                        {
                                this->condvar->wait(this->condvar, this->lock);
                        }
                        this->lock->unlock(this->lock);
                }
                return status;
        }
        else
        {
                entry->addr->refcount--;
        }
        DBG2(DBG_KNL, "virtual IP %H used by other SAs, not deleting",
                 virtual_ip);
        this->lock->unlock(this->lock);
        return SUCCESS;
}

/**
 * Manages source routes in the routing table.
 * By setting the appropriate nlmsg_type, the route gets added or removed.
 */
static status_t manage_srcroute(private_kernel_netlink_net_t *this,
                                                                int nlmsg_type, int flags, chunk_t dst_net,
                                                                uint8_t prefixlen, host_t *gateway,
                                                                host_t *src_ip, char *if_name)
{
        netlink_buf_t request;
        struct nlmsghdr *hdr;
        struct rtmsg *msg;
        struct rtattr *rta;
        int ifindex;
        chunk_t chunk;

        /* if route is 0.0.0.0/0, we can't install it, as it would
         * overwrite the default route. Instead, we add two routes:
         * 0.0.0.0/1 and 128.0.0.0/1 */
        if (this->routing_table == 0 && prefixlen == 0)
        {
                chunk_t half_net;
                uint8_t half_prefixlen;
                status_t status;

                half_net = chunk_alloca(dst_net.len);
                memset(half_net.ptr, 0, half_net.len);
                half_prefixlen = 1;

                status = manage_srcroute(this, nlmsg_type, flags, half_net,
                                                                 half_prefixlen, gateway, src_ip, if_name);
                half_net.ptr[0] |= 0x80;
                status |= manage_srcroute(this, nlmsg_type, flags, half_net,
                                                                  half_prefixlen, gateway, src_ip, if_name);
                return status;
        }

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

        hdr = &request.hdr;
        hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
        hdr->nlmsg_type = nlmsg_type;
        hdr->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));

        msg = NLMSG_DATA(hdr);
        msg->rtm_family = src_ip->get_family(src_ip);
        msg->rtm_dst_len = prefixlen;
        msg->rtm_protocol = RTPROT_STATIC;
        msg->rtm_type = RTN_UNICAST;
        msg->rtm_scope = RT_SCOPE_UNIVERSE;

        if (this->routing_table < 256)
        {
                msg->rtm_table = this->routing_table;
        }
        else
        {
#ifdef HAVE_RTA_TABLE
                chunk = chunk_from_thing(this->routing_table);
                netlink_add_attribute(hdr, RTA_TABLE, chunk, sizeof(request));
#else
                DBG1(DBG_KNL, "routing table IDs > 255 are not supported");
                return FAILED;
#endif /* HAVE_RTA_TABLE */
        }
        netlink_add_attribute(hdr, RTA_DST, dst_net, sizeof(request));
        chunk = src_ip->get_address(src_ip);
        netlink_add_attribute(hdr, RTA_PREFSRC, chunk, sizeof(request));
        if (gateway && gateway->get_family(gateway) == src_ip->get_family(src_ip))
        {
                chunk = gateway->get_address(gateway);
                netlink_add_attribute(hdr, RTA_GATEWAY, chunk, sizeof(request));
        }
        ifindex = get_interface_index(this, if_name);
        chunk.ptr = (char*)&ifindex;
        chunk.len = sizeof(ifindex);
        netlink_add_attribute(hdr, RTA_OIF, chunk, sizeof(request));

        if (this->mtu || this->mss)
        {
                chunk = chunk_alloca(RTA_LENGTH((sizeof(struct rtattr) +
                                                                                 sizeof(uint32_t)) * 2));
                chunk.len = 0;
                rta = (struct rtattr*)chunk.ptr;
                if (this->mtu)
                {
                        rta->rta_type = RTAX_MTU;
                        rta->rta_len = RTA_LENGTH(sizeof(uint32_t));
                        memcpy(RTA_DATA(rta), &this->mtu, sizeof(uint32_t));
                        chunk.len = rta->rta_len;
                }
                if (this->mss)
                {
                        rta = (struct rtattr*)(chunk.ptr + RTA_ALIGN(chunk.len));
                        rta->rta_type = RTAX_ADVMSS;
                        rta->rta_len = RTA_LENGTH(sizeof(uint32_t));
                        memcpy(RTA_DATA(rta), &this->mss, sizeof(uint32_t));
                        chunk.len = RTA_ALIGN(chunk.len) + rta->rta_len;
                }
                netlink_add_attribute(hdr, RTA_METRICS, chunk, sizeof(request));
        }

        return this->socket->send_ack(this->socket, hdr);
}

/**
 * Helper struct used to check routes
 */
typedef struct {
        /** the entry we look for */
        route_entry_t route;
        /** kernel interface */
        private_kernel_netlink_net_t *this;
} route_entry_lookup_t;

/**
 * Check if a matching route entry has a VIP associated
 */
static bool route_with_vip(route_entry_lookup_t *a, route_entry_t *b)
{
        if (chunk_equals(a->route.dst_net, b->dst_net) &&
                a->route.prefixlen == b->prefixlen &&
                is_known_vip(a->this, b->src_ip))
        {
                return TRUE;
        }
        return FALSE;
}

/**
 * Check if there is any route entry with a matching destination
 */
static bool route_with_dst(route_entry_lookup_t *a, route_entry_t *b)
{
        if (chunk_equals(a->route.dst_net, b->dst_net) &&
                a->route.prefixlen == b->prefixlen)
        {
                return TRUE;
        }
        return FALSE;
}

METHOD(kernel_net_t, add_route, status_t,
        private_kernel_netlink_net_t *this, chunk_t dst_net, uint8_t prefixlen,
        host_t *gateway, host_t *src_ip, char *if_name)
{
        status_t status;
        route_entry_t *found;
        route_entry_lookup_t lookup = {
                .route = {
                        .dst_net = dst_net,
                        .prefixlen = prefixlen,
                        .gateway = gateway,
                        .src_ip = src_ip,
                        .if_name = if_name,
                },
                .this = this,
        };

        this->routes_lock->lock(this->routes_lock);
        found = this->routes->get(this->routes, &lookup.route);
        if (found)
        {
                this->routes_lock->unlock(this->routes_lock);
                return ALREADY_DONE;
        }

        /* don't replace the route if we already have one with a VIP installed,
         * but keep track of it in case that other route is uninstalled */
        this->lock->read_lock(this->lock);
        if (!is_known_vip(this, src_ip))
        {
                found = this->routes->get_match(this->routes, &lookup,
                                                                                (void*)route_with_vip);
        }
        this->lock->unlock(this->lock);
        if (found)
        {
                status = SUCCESS;
        }
        else
        {
                status = manage_srcroute(this, RTM_NEWROUTE, NLM_F_CREATE|NLM_F_REPLACE,
                                                                 dst_net, prefixlen, gateway, src_ip, if_name);
        }
        if (status == SUCCESS)
        {
                found = route_entry_clone(&lookup.route);
                this->routes->put(this->routes, found, found);
        }
        this->routes_lock->unlock(this->routes_lock);
        return status;
}

METHOD(kernel_net_t, del_route, status_t,
        private_kernel_netlink_net_t *this, chunk_t dst_net, uint8_t prefixlen,
        host_t *gateway, host_t *src_ip, char *if_name)
{
        status_t status;
        route_entry_t *found;
        route_entry_lookup_t lookup = {
                .route = {
                        .dst_net = dst_net,
                        .prefixlen = prefixlen,
                        .gateway = gateway,
                        .src_ip = src_ip,
                        .if_name = if_name,
                },
                .this = this,
        };

        this->routes_lock->lock(this->routes_lock);
        found = this->routes->remove(this->routes, &lookup.route);
        if (!found)
        {
                this->routes_lock->unlock(this->routes_lock);
                return NOT_FOUND;
        }
        route_entry_destroy(found);

        /* check if there are any other routes for the same destination and if
         * so update the route, otherwise uninstall it */
        this->lock->read_lock(this->lock);
        found = this->routes->get_match(this->routes, &lookup,
                                                                        (void*)route_with_vip);
        this->lock->unlock(this->lock);
        if (!found)
        {
                found = this->routes->get_match(this->routes, &lookup,
                                                                                (void*)route_with_dst);
        }
        if (found)
        {
                status = manage_srcroute(this, RTM_NEWROUTE, NLM_F_CREATE|NLM_F_REPLACE,
                                                        found->dst_net, found->prefixlen, found->gateway,
                                                        found->src_ip, found->if_name);
        }
        else
        {
                status = manage_srcroute(this, RTM_DELROUTE, 0, dst_net, prefixlen,
                                                                 gateway, src_ip, if_name);
        }
        this->routes_lock->unlock(this->routes_lock);
        return status;
}

/**
 * Initialize a list of local addresses.
 */