source: trunk/server/source4/nbt_server/wins/winsserver.c

/* 
   Unix SMB/CIFS implementation.

   core wins server handling

   Copyright (C) Andrew Tridgell        2005
   Copyright (C) Stefan Metzmacher      2005
      
   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 3 of the License, or
   (at your option) any later version.
   
   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.
   
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "lib/util/dlinklist.h"
#include "nbt_server/nbt_server.h"
#include "nbt_server/wins/winsdb.h"
#include "nbt_server/wins/winsserver.h"
#include "librpc/gen_ndr/ndr_nbt.h"
#include "system/time.h"
#include "libcli/composite/composite.h"
#include "smbd/service_task.h"
#include "system/network.h"
#include "lib/socket/socket.h"
#include "lib/socket/netif.h"
#include <ldb.h>
#include "param/param.h"
#include "libcli/resolve/resolve.h"
#include "lib/util/util_net.h"

/*
  work out the ttl we will use given a client requested ttl
*/
uint32_t wins_server_ttl(struct wins_server *winssrv, uint32_t ttl)
{
        ttl = MIN(ttl, winssrv->config.max_renew_interval);
        ttl = MAX(ttl, winssrv->config.min_renew_interval);
        return ttl;
}

static enum wrepl_name_type wrepl_type(uint16_t nb_flags, struct nbt_name *name, bool mhomed)
{
        /* this copes with the nasty hack that is the type 0x1c name */
        if (name->type == NBT_NAME_LOGON) {
                return WREPL_TYPE_SGROUP;
        }
        if (nb_flags & NBT_NM_GROUP) {
                return WREPL_TYPE_GROUP;
        }
        if (mhomed) {
                return WREPL_TYPE_MHOMED;
        }
        return WREPL_TYPE_UNIQUE;
}

/*
  register a new name with WINS
*/
static uint8_t wins_register_new(struct nbt_name_socket *nbtsock, 
                                 struct nbt_name_packet *packet, 
                                 const struct socket_address *src,
                                 enum wrepl_name_type type)
{
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        struct nbt_name *name = &packet->questions[0].name;
        uint32_t ttl = wins_server_ttl(winssrv, packet->additional[0].ttl);
        uint16_t nb_flags = packet->additional[0].rdata.netbios.addresses[0].nb_flags;
        const char *address = packet->additional[0].rdata.netbios.addresses[0].ipaddr;
        struct winsdb_record rec;
        enum wrepl_name_node node;

#define WREPL_NODE_NBT_FLAGS(nb_flags) \
        ((nb_flags & NBT_NM_OWNER_TYPE)>>13)

        node    = WREPL_NODE_NBT_FLAGS(nb_flags);

        rec.name                = name;
        rec.type                = type;
        rec.state               = WREPL_STATE_ACTIVE;
        rec.node                = node;
        rec.is_static           = false;
        rec.expire_time         = time(NULL) + ttl;
        rec.version             = 0; /* will be allocated later */
        rec.wins_owner          = NULL; /* will be set later */
        rec.registered_by       = src->addr;
        rec.addresses           = winsdb_addr_list_make(packet);
        if (rec.addresses == NULL) return NBT_RCODE_SVR;

        rec.addresses     = winsdb_addr_list_add(winssrv->wins_db,
                                                 &rec, rec.addresses,
                                                 address,
                                                 winssrv->wins_db->local_owner,
                                                 rec.expire_time,
                                                 true);
        if (rec.addresses == NULL) return NBT_RCODE_SVR;

        DEBUG(4,("WINS: accepted registration of %s with address %s\n",
                 nbt_name_string(packet, name), rec.addresses[0]->address));
        
        return winsdb_add(winssrv->wins_db, &rec, WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP);
}


/*
  update the ttl on an existing record
*/
static uint8_t wins_update_ttl(struct nbt_name_socket *nbtsock, 
                               struct nbt_name_packet *packet, 
                               struct winsdb_record *rec,
                               struct winsdb_addr *winsdb_addr,
                               const struct socket_address *src)
{
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        uint32_t ttl = wins_server_ttl(winssrv, packet->additional[0].ttl);
        const char *address = packet->additional[0].rdata.netbios.addresses[0].ipaddr;
        uint32_t modify_flags = 0;

        rec->expire_time   = time(NULL) + ttl;
        rec->registered_by = src->addr;

        if (winsdb_addr) {
                rec->addresses = winsdb_addr_list_add(winssrv->wins_db,
                                                      rec, rec->addresses,
                                                      winsdb_addr->address,
                                                      winssrv->wins_db->local_owner,
                                                      rec->expire_time,
                                                      true);
                if (rec->addresses == NULL) return NBT_RCODE_SVR;
        }

        if (strcmp(winssrv->wins_db->local_owner, rec->wins_owner) != 0) {
                modify_flags = WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP;
        }

        DEBUG(5,("WINS: refreshed registration of %s at %s\n",
                 nbt_name_string(packet, rec->name), address));
        
        return winsdb_modify(winssrv->wins_db, rec, modify_flags);
}

/*
  do a sgroup merge
*/
static uint8_t wins_sgroup_merge(struct nbt_name_socket *nbtsock, 
                                 struct nbt_name_packet *packet, 
                                 struct winsdb_record *rec,
                                 const char *address,
                                 const struct socket_address *src)
{
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        uint32_t ttl = wins_server_ttl(winssrv, packet->additional[0].ttl);

        rec->expire_time   = time(NULL) + ttl;
        rec->registered_by = src->addr;

        rec->addresses     = winsdb_addr_list_add(winssrv->wins_db,
                                                  rec, rec->addresses,
                                                  address,
                                                  winssrv->wins_db->local_owner,
                                                  rec->expire_time,
                                                  true);
        if (rec->addresses == NULL) return NBT_RCODE_SVR;

        DEBUG(5,("WINS: sgroup merge of %s at %s\n",
                 nbt_name_string(packet, rec->name), address));
        
        return winsdb_modify(winssrv->wins_db, rec, WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP);
}

struct nbtd_wins_wack_state {
        struct nbtd_wins_wack_state *prev, *next;
        struct wins_server *winssrv;
        struct nbt_name_socket *nbtsock;
        struct nbtd_interface *iface;
        struct nbt_name_packet *request_packet;
        struct winsdb_record *rec;
        struct socket_address *src;
        const char *reg_address;
        enum wrepl_name_type new_type;
        struct wins_challenge_io io;
        NTSTATUS status;
};

static int nbtd_wins_wack_state_destructor(struct nbtd_wins_wack_state *s)
{
        DLIST_REMOVE(s->iface->wack_queue, s);
        return 0;
}

static bool wins_check_wack_queue(struct nbtd_interface *iface,
                                  struct nbt_name_packet *packet,
                                  struct socket_address *src)
{
        struct nbtd_wins_wack_state *s;

        for (s= iface->wack_queue; s; s = s->next) {
                if (packet->name_trn_id != s->request_packet->name_trn_id) {
                        continue;
                }
                if (packet->operation != s->request_packet->operation) {
                        continue;
                }
                if (src->port != s->src->port) {
                        continue;
                }
                if (strcmp(src->addr, s->src->addr) != 0) {
                        continue;
                }

                return true;
        }

        return false;
}

/*
  deny a registration request
*/
static void wins_wack_deny(struct nbtd_wins_wack_state *s)
{
        nbtd_name_registration_reply(s->nbtsock, s->request_packet, 
                                     s->src, NBT_RCODE_ACT);
        DEBUG(4,("WINS: denied name registration request for %s from %s:%d\n",
                 nbt_name_string(s, s->rec->name), s->src->addr, s->src->port));
        talloc_free(s);
}

/*
  allow a registration request
*/
static void wins_wack_allow(struct nbtd_wins_wack_state *s)
{
        NTSTATUS status;
        uint32_t ttl = wins_server_ttl(s->winssrv, s->request_packet->additional[0].ttl);
        struct winsdb_record *rec = s->rec, *rec2;
        uint32_t i,j;

        status = winsdb_lookup(s->winssrv->wins_db, rec->name, s, &rec2);
        if (!NT_STATUS_IS_OK(status) ||
            rec2->version != rec->version ||
            strcmp(rec2->wins_owner, rec->wins_owner) != 0) {
                DEBUG(5,("WINS: record %s changed during WACK - failing registration\n",
                         nbt_name_string(s, rec->name)));
                wins_wack_deny(s);
                return;
        }

        /*
         * if the old name owner doesn't hold the name anymore
         * handle the request as new registration for the new name owner
         */
        if (!NT_STATUS_IS_OK(s->status)) {
                uint8_t rcode;

                winsdb_delete(s->winssrv->wins_db, rec);
                rcode = wins_register_new(s->nbtsock, s->request_packet, s->src, s->new_type);
                if (rcode != NBT_RCODE_OK) {
                        DEBUG(1,("WINS: record %s failed to register as new during WACK\n",
                                 nbt_name_string(s, rec->name)));
                        wins_wack_deny(s);
                        return;
                }
                goto done;
        }

        rec->expire_time = time(NULL) + ttl;
        rec->registered_by = s->src->addr;

        /*
         * now remove all addresses that the client doesn't hold anymore
         * and update the time stamp and owner for the ones that are still there
         */
        for (i=0; rec->addresses[i]; i++) {
                bool found = false;
                for (j=0; j < s->io.out.num_addresses; j++) {
                        if (strcmp(rec->addresses[i]->address, s->io.out.addresses[j]) != 0) continue;

                        found = true;
                        break;
                }
                if (found) {
                        rec->addresses = winsdb_addr_list_add(s->winssrv->wins_db,
                                                              rec, rec->addresses,
                                                              s->reg_address,
                                                              s->winssrv->wins_db->local_owner,
                                                              rec->expire_time,
                                                              true);
                        if (rec->addresses == NULL) goto failed;
                        continue;
                }

                winsdb_addr_list_remove(rec->addresses, rec->addresses[i]->address);
        }

        rec->addresses = winsdb_addr_list_add(s->winssrv->wins_db,
                                              rec, rec->addresses,
                                              s->reg_address,
                                              s->winssrv->wins_db->local_owner,
                                              rec->expire_time,
                                              true);
        if (rec->addresses == NULL) goto failed;

        /* if we have more than one address, this becomes implicit a MHOMED record */
        if (winsdb_addr_list_length(rec->addresses) > 1) {
                rec->type = WREPL_TYPE_MHOMED;
        }

        winsdb_modify(s->winssrv->wins_db, rec, WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP);

        DEBUG(4,("WINS: accepted registration of %s with address %s\n",
                 nbt_name_string(s, rec->name), s->reg_address));

done:
        nbtd_name_registration_reply(s->nbtsock, s->request_packet, 
                                     s->src, NBT_RCODE_OK);
failed:
        talloc_free(s);
}

/*
  called when a name query to a current owner completes
*/
static void wack_wins_challenge_handler(struct composite_context *c_req)
{
        struct nbtd_wins_wack_state *s = talloc_get_type(c_req->async.private_data,
                                         struct nbtd_wins_wack_state);
        bool found;
        uint32_t i;

        s->status = wins_challenge_recv(c_req, s, &s->io);

        /*
         * if the owner denies it holds the name, then allow
         * the registration
         */
        if (!NT_STATUS_IS_OK(s->status)) {
                wins_wack_allow(s);
                return;
        }

        if (s->new_type == WREPL_TYPE_GROUP || s->new_type == WREPL_TYPE_SGROUP) {
                DEBUG(1,("WINS: record %s failed to register as group type(%u) during WACK, it's still type(%u)\n",
                         nbt_name_string(s, s->rec->name), s->new_type, s->rec->type));
                wins_wack_deny(s);
                return;
        }

        /*
         * if the owner still wants the name and doesn't reply
         * with the address trying to be registered, then deny
         * the registration
         */
        found = false;
        for (i=0; i < s->io.out.num_addresses; i++) {
                if (strcmp(s->reg_address, s->io.out.addresses[i]) != 0) continue;

                found = true;
                break;
        }
        if (!found) {
                wins_wack_deny(s);
                return;
        }

        wins_wack_allow(s);
        return;
}


/*
  a client has asked to register a unique name that someone else owns. We
  need to ask each of the current owners if they still want it. If they do
  then reject the registration, otherwise allow it
*/
static void wins_register_wack(struct nbt_name_socket *nbtsock, 
                               struct nbt_name_packet *packet, 
                               struct winsdb_record *rec,
                               struct socket_address *src,
                               enum wrepl_name_type new_type)
{
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        struct nbtd_wins_wack_state *s;
        struct composite_context *c_req;
        uint32_t ttl;

        s = talloc_zero(nbtsock, struct nbtd_wins_wack_state);
        if (s == NULL) goto failed;

        /* package up the state variables for this wack request */
        s->winssrv              = winssrv;
        s->nbtsock              = nbtsock;
        s->iface                = iface;
        s->request_packet       = talloc_steal(s, packet);
        s->rec                  = talloc_steal(s, rec);
        s->reg_address          = packet->additional[0].rdata.netbios.addresses[0].ipaddr;
        s->new_type             = new_type;
        s->src                  = src;
        if (talloc_reference(s, src) == NULL) goto failed;

        s->io.in.nbtd_server    = iface->nbtsrv;
        s->io.in.nbt_port       = lpcfg_nbt_port(iface->nbtsrv->task->lp_ctx);
        s->io.in.event_ctx      = iface->nbtsrv->task->event_ctx;
        s->io.in.name           = rec->name;
        s->io.in.num_addresses  = winsdb_addr_list_length(rec->addresses);
        s->io.in.addresses      = winsdb_addr_string_list(s, rec->addresses);
        if (s->io.in.addresses == NULL) goto failed;

        DLIST_ADD_END(iface->wack_queue, s, struct nbtd_wins_wack_state *);

        talloc_set_destructor(s, nbtd_wins_wack_state_destructor);

        /*
         * send a WACK to the client, specifying the maximum time it could
         * take to check with the owner, plus some slack
         */
        ttl = 5 + 4 * winsdb_addr_list_length(rec->addresses);
        nbtd_wack_reply(nbtsock, packet, src, ttl);

        /*
         * send the challenge to the old addresses
         */
        c_req = wins_challenge_send(s, &s->io);
        if (c_req == NULL) goto failed;

        c_req->async.fn                 = wack_wins_challenge_handler;
        c_req->async.private_data       = s;
        return;

failed:
        talloc_free(s);
        nbtd_name_registration_reply(nbtsock, packet, src, NBT_RCODE_SVR);
}

/*
  register a name
*/
static void nbtd_winsserver_register(struct nbt_name_socket *nbtsock, 
                                     struct nbt_name_packet *packet, 
                                     struct socket_address *src)
{
        NTSTATUS status;
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        struct nbt_name *name = &packet->questions[0].name;
        struct winsdb_record *rec;
        uint8_t rcode = NBT_RCODE_OK;
        uint16_t nb_flags = packet->additional[0].rdata.netbios.addresses[0].nb_flags;
        const char *address = packet->additional[0].rdata.netbios.addresses[0].ipaddr;
        bool mhomed = ((packet->operation & NBT_OPCODE) == NBT_OPCODE_MULTI_HOME_REG);
        enum wrepl_name_type new_type = wrepl_type(nb_flags, name, mhomed);
        struct winsdb_addr *winsdb_addr = NULL;
        bool duplicate_packet;

        /*
         * as a special case, the local master browser name is always accepted
         * for registration, but never stored, but w2k3 stores it if it's registered
         * as a group name, (but a query for the 0x1D name still returns not found!)
         */
        if (name->type == NBT_NAME_MASTER && !(nb_flags & NBT_NM_GROUP)) {
                rcode = NBT_RCODE_OK;
                goto done;
        }

        /* w2k3 refuses 0x1B names with marked as group */
        if (name->type == NBT_NAME_PDC && (nb_flags & NBT_NM_GROUP)) {
                rcode = NBT_RCODE_RFS;
                goto done;
        }

        /* w2k3 refuses 0x1C names with out marked as group */
        if (name->type == NBT_NAME_LOGON && !(nb_flags & NBT_NM_GROUP)) {
                rcode = NBT_RCODE_RFS;
                goto done;
        }

        /* w2k3 refuses 0x1E names with out marked as group */
        if (name->type == NBT_NAME_BROWSER && !(nb_flags & NBT_NM_GROUP)) {
                rcode = NBT_RCODE_RFS;
                goto done;
        }

        if (name->scope && strlen(name->scope) > 237) {
                rcode = NBT_RCODE_SVR;
                goto done;
        }

        duplicate_packet = wins_check_wack_queue(iface, packet, src);
        if (duplicate_packet) {
                /* just ignore the packet */
                DEBUG(5,("Ignoring duplicate packet while WACK is pending from %s:%d\n",
                         src->addr, src->port));
                return;
        }

        status = winsdb_lookup(winssrv->wins_db, name, packet, &rec);
        if (NT_STATUS_EQUAL(NT_STATUS_OBJECT_NAME_NOT_FOUND, status)) {
                rcode = wins_register_new(nbtsock, packet, src, new_type);
                goto done;
        } else if (!NT_STATUS_IS_OK(status)) {
                rcode = NBT_RCODE_SVR;
                goto done;
        } else if (rec->is_static) {
                if (rec->type == WREPL_TYPE_GROUP || rec->type == WREPL_TYPE_SGROUP) {
                        rcode = NBT_RCODE_OK;
                        goto done;
                }
                rcode = NBT_RCODE_ACT;
                goto done;
        }

        if (rec->type == WREPL_TYPE_GROUP) {
                if (new_type != WREPL_TYPE_GROUP) {
                        DEBUG(2,("WINS: Attempt to register name %s as non normal group(%u)"
                                 " while a normal group is already there\n",
                                 nbt_name_string(packet, name), new_type));
                        rcode = NBT_RCODE_ACT;
                        goto done;
                }

                if (rec->state == WREPL_STATE_ACTIVE) {
                        /* TODO: is this correct? */
                        rcode = wins_update_ttl(nbtsock, packet, rec, NULL, src);
                        goto done;
                }

                /* TODO: is this correct? */
                winsdb_delete(winssrv->wins_db, rec);
                rcode = wins_register_new(nbtsock, packet, src, new_type);
                goto done;
        }

        if (rec->state != WREPL_STATE_ACTIVE) {
                winsdb_delete(winssrv->wins_db, rec);
                rcode = wins_register_new(nbtsock, packet, src, new_type);
                goto done;
        }

        switch (rec->type) {
        case WREPL_TYPE_UNIQUE:
        case WREPL_TYPE_MHOMED:
                /* 
                 * if its an active unique name, and the registration is for a group, then
                 * see if the unique name owner still wants the name
                 * TODO: is this correct?
                 */
                if (new_type == WREPL_TYPE_GROUP || new_type == WREPL_TYPE_GROUP) {
                        wins_register_wack(nbtsock, packet, rec, src, new_type);
                        return;
                }

                /* 
                 * if the registration is for an address that is currently active, then 
                 * just update the expiry time of the record and the address
                 */
                winsdb_addr = winsdb_addr_list_check(rec->addresses, address);
                if (winsdb_addr) {
                        rcode = wins_update_ttl(nbtsock, packet, rec, winsdb_addr, src);
                        goto done;
                }

                /*
                 * we have to do a WACK to see if the current owner is willing
                 * to give up its claim
                 */
                wins_register_wack(nbtsock, packet, rec, src, new_type);
                return;

        case WREPL_TYPE_GROUP:
                /* this should not be reached as normal groups are handled above */
                DEBUG(0,("BUG at %s\n",__location__));
                rcode = NBT_RCODE_ACT;
                goto done;

        case WREPL_TYPE_SGROUP:
                /* if the new record isn't also a special group, refuse the registration */ 
                if (new_type != WREPL_TYPE_SGROUP) {
                        DEBUG(2,("WINS: Attempt to register name %s as non special group(%u)"
                                 " while a special group is already there\n",
                                 nbt_name_string(packet, name), new_type));
                        rcode = NBT_RCODE_ACT;
                        goto done;
                }

                /* 
                 * if the registration is for an address that is currently active, then 
                 * just update the expiry time of the record and the address
                 */
                winsdb_addr = winsdb_addr_list_check(rec->addresses, address);
                if (winsdb_addr) {
                        rcode = wins_update_ttl(nbtsock, packet, rec, winsdb_addr, src);
                        goto done;
                }

                rcode = wins_sgroup_merge(nbtsock, packet, rec, address, src);
                goto done;
        }

done:
        nbtd_name_registration_reply(nbtsock, packet, src, rcode);
}

static uint32_t ipv4_match_bits(struct in_addr ip1, struct in_addr ip2)
{
        uint32_t i, j, match=0;
        uint8_t *p1, *p2;

        p1 = (uint8_t *)&ip1.s_addr;
        p2 = (uint8_t *)&ip2.s_addr;

        for (i=0; i<4; i++) {
                if (p1[i] != p2[i]) break;
                match += 8;
        }

        if (i==4) return match;

        for (j=0; j<8; j++) {
                if ((p1[i] & (1<<(7-j))) != (p2[i] & (1<<(7-j))))
                        break;
                match++;
        }

        return match;
}

static int nbtd_wins_randomize1Clist_sort(void *p1,/* (const char **) */
                                          void *p2,/* (const char **) */
                                          struct socket_address *src)
{
        const char *a1 = (const char *)*(const char **)p1;
        const char *a2 = (const char *)*(const char **)p2;
        uint32_t match_bits1;
        uint32_t match_bits2;

        match_bits1 = ipv4_match_bits(interpret_addr2(a1), interpret_addr2(src->addr));
        match_bits2 = ipv4_match_bits(interpret_addr2(a2), interpret_addr2(src->addr));

        return match_bits2 - match_bits1;
}

static void nbtd_wins_randomize1Clist(struct loadparm_context *lp_ctx,
                                      const char **addresses, struct socket_address *src)
{
        const char *mask;
        const char *tmp;
        uint32_t num_addrs;
        uint32_t idx, sidx;
        int r;

        for (num_addrs=0; addresses[num_addrs]; num_addrs++) { /* noop */ }

        if (num_addrs <= 1) return; /* nothing to do */

        /* first sort the addresses depending on the matching to the client */
        LDB_TYPESAFE_QSORT(addresses, num_addrs, src, nbtd_wins_randomize1Clist_sort);

        mask = lpcfg_parm_string(lp_ctx, NULL, "nbtd", "wins_randomize1Clist_mask");
        if (!mask) {
                mask = "255.255.255.0";
        }

        /* 
         * choose a random address to be the first in the response to the client,
         * preferr the addresses inside the nbtd:wins_randomize1Clist_mask netmask
         */
        r = random();
        idx = sidx = r % num_addrs;

        while (1) {
                bool same;

                /* if the current one is in the same subnet, use it */
                same = iface_same_net(addresses[idx], src->addr, mask);
                if (same) {
                        sidx = idx;
                        break;
                }

                /* we need to check for idx == 0, after checking for the same net */
                if (idx == 0) break;
                /* 
                 * if we haven't found an address in the same subnet, search in ones
                 * which match the client more
                 *
                 * some notes:
                 *
                 * it's not "idx = idx % r" but "idx = r % idx"
                 * because in "a % b" b is the allowed range
                 * and b-1 is the maximum possible result, so it must be decreasing
                 * and the above idx == 0 check breaks the while(1) loop.
                 */
                idx = r % idx;
        }

        /* note sidx == 0 is also valid here ... */
        tmp             = addresses[0];
        addresses[0]    = addresses[sidx];
        addresses[sidx] = tmp;
}

/*
  query a name
*/
static void nbtd_winsserver_query(struct loadparm_context *lp_ctx,
                                  struct nbt_name_socket *nbtsock, 
                                  struct nbt_name_packet *packet, 
                                  struct socket_address *src)
{
        NTSTATUS status;
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        struct nbt_name *name = &packet->questions[0].name;
        struct winsdb_record *rec;
        struct winsdb_record *rec_1b = NULL;
        const char **addresses;
        const char **addresses_1b = NULL;
        uint16_t nb_flags = 0;

        if (name->type == NBT_NAME_MASTER) {
                goto notfound;
        }

        /*
         * w2k3 returns the first address of the 0x1B record as first address
         * to a 0x1C query
         *
         * since Windows 2000 Service Pack 2 there's on option to trigger this behavior:
         *
         * HKEY_LOCAL_MACHINE\System\CurrentControlset\Services\WINS\Parameters\Prepend1BTo1CQueries
         * Typ: Daten REG_DWORD
         * Value: 0 = deactivated, 1 = activated
         */
        if (name->type == NBT_NAME_LOGON && 
            lpcfg_parm_bool(lp_ctx, NULL, "nbtd", "wins_prepend1Bto1Cqueries", true)) {
                struct nbt_name name_1b;

                name_1b = *name;
                name_1b.type = NBT_NAME_PDC;

                status = winsdb_lookup(winssrv->wins_db, &name_1b, packet, &rec_1b);
                if (NT_STATUS_IS_OK(status)) {
                        addresses_1b = winsdb_addr_string_list(packet, rec_1b->addresses);
                }
        }

        status = winsdb_lookup(winssrv->wins_db, name, packet, &rec);
        if (!NT_STATUS_IS_OK(status)) {
                if (!lpcfg_wins_dns_proxy(lp_ctx)) {
                        goto notfound;
                }

                if (name->type != NBT_NAME_CLIENT && name->type != NBT_NAME_SERVER) {
                        goto notfound;
                }

                nbtd_wins_dns_proxy_query(nbtsock, packet, src);
                return;
        }

        /*
         * for group's we always reply with
         * 255.255.255.255 as address, even if
         * the record is released or tombstoned
         */
        if (rec->type == WREPL_TYPE_GROUP) {
                addresses = str_list_add(NULL, "255.255.255.255");
                talloc_steal(packet, addresses);
                if (!addresses) {
                        goto notfound;
                }
                nb_flags |= NBT_NM_GROUP;
                goto found;
        }

        if (rec->state != WREPL_STATE_ACTIVE) {
                goto notfound;
        }

        addresses = winsdb_addr_string_list(packet, rec->addresses);
        if (!addresses) {
                goto notfound;
        }

        /* 
         * if addresses_1b isn't NULL, we have a 0x1C query and need to return the
         * first 0x1B address as first address
         */
        if (addresses_1b && addresses_1b[0]) {
                const char **addresses_1c = addresses;
                uint32_t i;
                uint32_t num_addrs;

                addresses = str_list_add(NULL, addresses_1b[0]);
                if (!addresses) {
                        goto notfound;
                }
                talloc_steal(packet, addresses);
                num_addrs = 1;

                for (i=0; addresses_1c[i]; i++) {
                        if (strcmp(addresses_1b[0], addresses_1c[i]) == 0) continue;

                        /*
                         * stop when we already have 25 addresses
                         */
                        if (num_addrs >= 25) break;

                        num_addrs++;                    
                        addresses = str_list_add(addresses, addresses_1c[i]);
                        if (!addresses) {
                                goto notfound;
                        }
                }
        }

        if (rec->type == WREPL_TYPE_SGROUP) {
                nb_flags |= NBT_NM_GROUP;
        } else {
                nb_flags |= (rec->node <<13);
        }

        /*
         * since Windows 2000 Service Pack 2 there's on option to trigger this behavior:
         *
         * HKEY_LOCAL_MACHINE\System\CurrentControlset\Services\WINS\Parameters\Randomize1CList
         * Typ: Daten REG_DWORD
         * Value: 0 = deactivated, 1 = activated
         */
        if (name->type == NBT_NAME_LOGON && 
            lpcfg_parm_bool(lp_ctx, NULL, "nbtd", "wins_randomize1Clist", false)) {
                nbtd_wins_randomize1Clist(lp_ctx, addresses, src);
        }

found:
        nbtd_name_query_reply(nbtsock, packet, src, name, 
                              0, nb_flags, addresses);
        return;

notfound:
        nbtd_negative_name_query_reply(nbtsock, packet, src);
}

/*
  release a name
*/
static void nbtd_winsserver_release(struct nbt_name_socket *nbtsock, 
                                    struct nbt_name_packet *packet, 
                                    struct socket_address *src)
{
        NTSTATUS status;
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        struct nbt_name *name = &packet->questions[0].name;
        struct winsdb_record *rec;
        uint32_t modify_flags = 0;
        uint8_t ret;

        if (name->type == NBT_NAME_MASTER) {
                goto done;
        }

        if (name->scope && strlen(name->scope) > 237) {
                goto done;
        }

        status = winsdb_lookup(winssrv->wins_db, name, packet, &rec);
        if (!NT_STATUS_IS_OK(status)) {
                goto done;
        }

        if (rec->is_static) {
                if (rec->type == WREPL_TYPE_UNIQUE || rec->type == WREPL_TYPE_MHOMED) {
                        goto done;
                }
                nbtd_name_release_reply(nbtsock, packet, src, NBT_RCODE_ACT);
                return;
        }

        if (rec->state != WREPL_STATE_ACTIVE) {
                goto done;
        }

        /* 
         * TODO: do we need to check if
         *       src->addr matches packet->additional[0].rdata.netbios.addresses[0].ipaddr
         *       here?
         */

        /* 
         * we only allow releases from an owner - other releases are
         * silently ignored
         */
        if (!winsdb_addr_list_check(rec->addresses, src->addr)) {
                int i;
                DEBUG(4,("WINS: silently ignoring attempted name release on %s from %s\n", nbt_name_string(rec, rec->name), src->addr));
                DEBUGADD(4, ("Registered Addresses: \n"));
                for (i=0; rec->addresses && rec->addresses[i]; i++) {
                        DEBUGADD(4, ("%s\n", rec->addresses[i]->address));
                }
                goto done;
        }

        DEBUG(4,("WINS: released name %s from %s\n", nbt_name_string(rec, rec->name), src->addr));

        switch (rec->type) {
        case WREPL_TYPE_UNIQUE:
                rec->state = WREPL_STATE_RELEASED;
                break;

        case WREPL_TYPE_GROUP:
                rec->state = WREPL_STATE_RELEASED;
                break;

        case WREPL_TYPE_SGROUP:
                winsdb_addr_list_remove(rec->addresses, src->addr);
                /* TODO: do we need to take the ownership here? */
                if (winsdb_addr_list_length(rec->addresses) == 0) {
                        rec->state = WREPL_STATE_RELEASED;
                }
                break;

        case WREPL_TYPE_MHOMED:
                winsdb_addr_list_remove(rec->addresses, src->addr);
                /* TODO: do we need to take the ownership here? */
                if (winsdb_addr_list_length(rec->addresses) == 0) {
                        rec->state = WREPL_STATE_RELEASED;
                }
                break;
        }

        if (rec->state == WREPL_STATE_ACTIVE) {
                /*
                 * If the record is still active, we need to update the
                 * expire_time.
                 *
                 * if we're not the owner, we need to take the ownership.
                 */
                rec->expire_time= time(NULL) + winssrv->config.max_renew_interval;
                if (strcmp(rec->wins_owner, winssrv->wins_db->local_owner) != 0) {
                        modify_flags = WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP;
                }
                if (lpcfg_parm_bool(iface->nbtsrv->task->lp_ctx, NULL, "wreplsrv", "propagate name releases", false)) {
                        /*
                         * We have an option to propagate every name release,
                         * this is off by default to match windows servers
                         */
                        modify_flags = WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP;
                }
        } else if (rec->state == WREPL_STATE_RELEASED) {
                /*
                 * if we're not the owner, we need to take the owner ship
                 * and make the record tombstone, but expire after
                 * tombstone_interval + tombstone_timeout and not only after tombstone_timeout
                 * like for normal tombstone records.
                 * This is to replicate the record directly to the original owner,
                 * where the record is still active
                 */ 
                if (strcmp(rec->wins_owner, winssrv->wins_db->local_owner) == 0) {
                        rec->expire_time= time(NULL) + winssrv->config.tombstone_interval;
                } else {
                        rec->state      = WREPL_STATE_TOMBSTONE;
                        rec->expire_time= time(NULL) + 
                                          winssrv->config.tombstone_interval +
                                          winssrv->config.tombstone_timeout;
                        modify_flags    = WINSDB_FLAG_ALLOC_VERSION | WINSDB_FLAG_TAKE_OWNERSHIP;
                }
        }

        ret = winsdb_modify(winssrv->wins_db, rec, modify_flags);
        if (ret != NBT_RCODE_OK) {
                DEBUG(1,("WINS: FAILED: released name %s at %s: error:%u\n",
                        nbt_name_string(rec, rec->name), src->addr, ret));
        }
done:
        /* we match w2k3 by always giving a positive reply to name releases. */
        nbtd_name_release_reply(nbtsock, packet, src, NBT_RCODE_OK);
}


/*
  answer a name query
*/
void nbtd_winsserver_request(struct nbt_name_socket *nbtsock, 
                             struct nbt_name_packet *packet, 
                             struct socket_address *src)
{
        struct nbtd_interface *iface = talloc_get_type(nbtsock->incoming.private_data,
                                                       struct nbtd_interface);
        struct wins_server *winssrv = iface->nbtsrv->winssrv;
        if ((packet->operation & NBT_FLAG_BROADCAST) || winssrv == NULL) {
                return;
        }

        switch (packet->operation & NBT_OPCODE) {
        case NBT_OPCODE_QUERY:
                nbtd_winsserver_query(iface->nbtsrv->task->lp_ctx, nbtsock, packet, src);
                break;

        case NBT_OPCODE_REGISTER:
        case NBT_OPCODE_REFRESH:
        case NBT_OPCODE_REFRESH2:
        case NBT_OPCODE_MULTI_HOME_REG:
                nbtd_winsserver_register(nbtsock, packet, src);
                break;

        case NBT_OPCODE_RELEASE:
                nbtd_winsserver_release(nbtsock, packet, src);
                break;
        }

}

/*
  startup the WINS server, if configured
*/
NTSTATUS nbtd_winsserver_init(struct nbtd_server *nbtsrv)
{
        uint32_t tmp;
        const char *owner;

        if (!lpcfg_wins_support(nbtsrv->task->lp_ctx)) {
                nbtsrv->winssrv = NULL;
                return NT_STATUS_OK;
        }

        nbtsrv->winssrv = talloc_zero(nbtsrv, struct wins_server);
        NT_STATUS_HAVE_NO_MEMORY(nbtsrv->winssrv);

        nbtsrv->winssrv->config.max_renew_interval = lpcfg_max_wins_ttl(nbtsrv->task->lp_ctx);
        nbtsrv->winssrv->config.min_renew_interval = lpcfg_min_wins_ttl(nbtsrv->task->lp_ctx);
        tmp = lpcfg_parm_int(nbtsrv->task->lp_ctx, NULL, "wreplsrv", "tombstone_interval", 6*24*60*60);
        nbtsrv->winssrv->config.tombstone_interval = tmp;
        tmp = lpcfg_parm_int(nbtsrv->task->lp_ctx, NULL, "wreplsrv"," tombstone_timeout", 1*24*60*60);
        nbtsrv->winssrv->config.tombstone_timeout = tmp;

        owner = lpcfg_parm_string(nbtsrv->task->lp_ctx, NULL, "winsdb", "local_owner");

        if (owner == NULL) {
                struct interface *ifaces;
                load_interfaces(nbtsrv->task, lpcfg_interfaces(nbtsrv->task->lp_ctx), &ifaces);
                owner = iface_n_ip(ifaces, 0);
        }

        nbtsrv->winssrv->wins_db     = winsdb_connect(nbtsrv->winssrv, nbtsrv->task->event_ctx, 
                                                      nbtsrv->task->lp_ctx,
                                                      owner, WINSDB_HANDLE_CALLER_NBTD);
        if (!nbtsrv->winssrv->wins_db) {
                return NT_STATUS_INTERNAL_DB_ERROR;
        }

        irpc_add_name(nbtsrv->task->msg_ctx, "wins_server");

        return NT_STATUS_OK;
}