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LU-9679 lnet: use LIST_HEAD() for local lists.
[fs/lustre-release.git] / lnet / lnet / router.c
index ce2f12d..cae8da6 100644 (file)
@@ -78,13 +78,17 @@ int avoid_asym_router_failure = 1;
 module_param(avoid_asym_router_failure, int, 0644);
 MODULE_PARM_DESC(avoid_asym_router_failure, "Avoid asymmetrical router failures (0 to disable)");
 
-static int dead_router_check_interval = 60;
-module_param(dead_router_check_interval, int, 0644);
-MODULE_PARM_DESC(dead_router_check_interval, "Seconds between dead router health checks (<= 0 to disable)");
+int dead_router_check_interval = INT_MIN;
+module_param(dead_router_check_interval, int, 0444);
+MODULE_PARM_DESC(dead_router_check_interval, "(DEPRECATED - Use alive_router_check_interval)");
 
-static int live_router_check_interval = 60;
-module_param(live_router_check_interval, int, 0644);
-MODULE_PARM_DESC(live_router_check_interval, "Seconds between live router health checks (<= 0 to disable)");
+int live_router_check_interval = INT_MIN;
+module_param(live_router_check_interval, int, 0444);
+MODULE_PARM_DESC(live_router_check_interval, "(DEPRECATED - Use alive_router_check_interval)");
+
+int alive_router_check_interval = 60;
+module_param(alive_router_check_interval, int, 0644);
+MODULE_PARM_DESC(alive_router_check_interval, "Seconds between live router health checks (<= 0 to disable)");
 
 static int router_ping_timeout = 50;
 module_param(router_ping_timeout, int, 0644);
@@ -145,102 +149,315 @@ rtr_sensitivity_set(const char *val, cfs_kernel_param_arg_t *kp)
        return 0;
 }
 
+void
+lnet_rtr_transfer_to_peer(struct lnet_peer *src, struct lnet_peer *target)
+{
+       struct lnet_route *route;
+
+       lnet_net_lock(LNET_LOCK_EX);
+       target->lp_rtr_refcount += src->lp_rtr_refcount;
+       /* move the list of queued messages to the new peer */
+       list_splice_init(&src->lp_rtrq, &target->lp_rtrq);
+       /* move all the routes that reference the peer */
+       list_splice_init(&src->lp_routes, &target->lp_routes);
+       /* update all the routes to point to the new peer */
+       list_for_each_entry(route, &target->lp_routes, lr_gwlist)
+               route->lr_gateway = target;
+       /* remove the old peer from the ln_routers list */
+       list_del_init(&src->lp_rtr_list);
+       /* add the new peer to the ln_routers list */
+       if (list_empty(&target->lp_rtr_list)) {
+               lnet_peer_addref_locked(target);
+               list_add_tail(&target->lp_rtr_list, &the_lnet.ln_routers);
+       }
+       /* reset the ref count on the old peer and decrement its ref count */
+       src->lp_rtr_refcount = 0;
+       lnet_peer_decref_locked(src);
+       /* update the router version */
+       the_lnet.ln_routers_version++;
+       lnet_net_unlock(LNET_LOCK_EX);
+}
+
 int
 lnet_peers_start_down(void)
 {
        return check_routers_before_use;
 }
 
-void
-lnet_notify_locked(struct lnet_peer_ni *lp, int notifylnd, int alive,
-                  time64_t when)
+/*
+ * The peer_net of a gateway is alive if at least one of the peer_ni's on
+ * that peer_net is alive.
+ */
+static bool
+lnet_is_gateway_net_alive(struct lnet_peer_net *lpn)
 {
-       if (lp->lpni_timestamp > when) { /* out of date information */
-               CDEBUG(D_NET, "Out of date\n");
-               return;
+       struct lnet_peer_ni *lpni;
+
+       list_for_each_entry(lpni, &lpn->lpn_peer_nis, lpni_peer_nis) {
+               if (lnet_is_peer_ni_alive(lpni))
+                       return true;
+       }
+
+       return false;
+}
+
+/*
+ * a gateway is alive only if all its nets are alive
+ * called with cpt lock held
+ */
+bool lnet_is_gateway_alive(struct lnet_peer *gw)
+{
+       struct lnet_peer_net *lpn;
+
+       if (!gw->lp_alive)
+               return false;
+
+       list_for_each_entry(lpn, &gw->lp_peer_nets, lpn_peer_nets) {
+               if (!lnet_is_gateway_net_alive(lpn))
+                       return false;
        }
 
+       return true;
+}
+
+/*
+ * lnet_is_route_alive() needs to be called with cpt lock held
+ * A route is alive if the gateway can route between the local network and
+ * the remote network of the route.
+ * This means at least one NI is alive on each of the local and remote
+ * networks of the gateway.
+ */
+bool lnet_is_route_alive(struct lnet_route *route)
+{
+       struct lnet_peer *gw = route->lr_gateway;
+       struct lnet_peer_net *llpn;
+       struct lnet_peer_net *rlpn;
+
+       /* If the gateway is down then all routes are considered down */
+       if (!gw->lp_alive)
+               return false;
+
        /*
-        * This function can be called with different cpt locks being
-        * held. lpni_alive_count modification needs to be properly protected.
-        * Significant reads to lpni_alive_count are also protected with
-        * the same lock
+        * if discovery is disabled then rely on the cached aliveness
+        * information. This is handicapped information which we log when
+        * we receive the discovery ping response. The most uptodate
+        * aliveness information can only be obtained when discovery is
+        * enabled.
         */
-       spin_lock(&lp->lpni_lock);
+       if (lnet_is_discovery_disabled(gw))
+               return route->lr_alive;
 
-       lp->lpni_timestamp = when; /* update timestamp */
+       /*
+        * check the gateway's interfaces on the local network
+        */
+       llpn = lnet_peer_get_net_locked(gw, route->lr_lnet);
+       if (!llpn)
+               return false;
+
+       if (!lnet_is_gateway_net_alive(llpn))
+               return false;
+
+       if (avoid_asym_router_failure) {
+               /* Check the gateway's interfaces on the remote network */
+               rlpn = lnet_peer_get_net_locked(gw, route->lr_net);
+               if (!rlpn)
+                       return false;
+               if (!lnet_is_gateway_net_alive(rlpn))
+                       return false;
+       }
 
-       if (lp->lpni_alive_count != 0 &&          /* got old news */
-           (!lp->lpni_alive) == (!alive)) {      /* new date for old news */
-               spin_unlock(&lp->lpni_lock);
-               CDEBUG(D_NET, "Old news\n");
-               return;
+       spin_lock(&gw->lp_lock);
+       if (!(gw->lp_state & LNET_PEER_ROUTER_ENABLED)) {
+               spin_unlock(&gw->lp_lock);
+               if (gw->lp_rtr_refcount > 0)
+                       CERROR("peer %s is being used as a gateway but routing feature is not turned on\n",
+                              libcfs_nid2str(gw->lp_primary_nid));
+               return false;
        }
+       spin_unlock(&gw->lp_lock);
 
-       /* Flag that notification is outstanding */
+       return true;
+}
 
-       lp->lpni_alive_count++;
-       lp->lpni_alive = (alive) ? 1 : 0;
-       lp->lpni_notify = 1;
-       lp->lpni_notifylnd = notifylnd;
-       if (lp->lpni_alive)
-               lp->lpni_ping_feats = LNET_PING_FEAT_INVAL; /* reset */
+void
+lnet_consolidate_routes_locked(struct lnet_peer *orig_lp,
+                              struct lnet_peer *new_lp)
+{
+       struct lnet_peer_ni *lpni;
+       struct lnet_route *route;
+
+       /*
+        * Although a route is correlated with a peer, but when it's added
+        * a specific NID is used. That NID refers to a peer_ni within
+        * a peer. There could be other peer_nis on the same net, which
+        * can be used to send to that gateway. However when we are
+        * consolidating gateways because of discovery, the nid used to
+        * add the route might've moved between gateway peers. In this
+        * case we want to move the route to the new gateway as well. The
+        * intent here is not to confuse the user who added the route.
+        */
+       list_for_each_entry(route, &orig_lp->lp_routes, lr_gwlist) {
+               lpni = lnet_peer_get_ni_locked(orig_lp, route->lr_nid);
+               if (!lpni) {
+                       lnet_net_lock(LNET_LOCK_EX);
+                       list_move(&route->lr_gwlist, &new_lp->lp_routes);
+                       lnet_net_unlock(LNET_LOCK_EX);
+               }
+       }
 
-       spin_unlock(&lp->lpni_lock);
+}
 
-       CDEBUG(D_NET, "set %s %d\n", libcfs_nid2str(lp->lpni_nid), alive);
+static inline void
+lnet_set_route_aliveness(struct lnet_route *route, bool alive)
+{
+       /* Log when there's a state change */
+       if (route->lr_alive != alive) {
+               CERROR("route to %s through %s has gone from %s to %s\n",
+                      libcfs_net2str(route->lr_net),
+                      libcfs_nid2str(route->lr_gateway->lp_primary_nid),
+                      (route->lr_alive) ? "up" : "down",
+                      alive ? "up" : "down");
+               route->lr_alive = alive;
+       }
 }
 
-/*
- * This function will always be called with lp->lpni_cpt lock held.
- */
-static void
-lnet_ni_notify_locked(struct lnet_ni *ni, struct lnet_peer_ni *lp)
+void
+lnet_router_discovery_ping_reply(struct lnet_peer *lp)
 {
-       int alive;
-       int notifylnd;
+       struct lnet_ping_buffer *pbuf = lp->lp_data;
+       struct lnet_remotenet *rnet;
+       struct lnet_peer_net *llpn;
+       struct lnet_route *route;
+       bool net_up = false;
+       unsigned lp_state;
+       __u32 net, net2;
+       int i, j;
 
-       /* Notify only in 1 thread at any time to ensure ordered notification.
-        * NB individual events can be missed; the only guarantee is that you
-        * always get the most recent news */
 
-       spin_lock(&lp->lpni_lock);
+       spin_lock(&lp->lp_lock);
+       lp_state = lp->lp_state;
 
-       if (lp->lpni_notifying || ni == NULL) {
-               spin_unlock(&lp->lpni_lock);
+       /* only handle replies if discovery is disabled. */
+       if (!lnet_is_discovery_disabled_locked(lp)) {
+               spin_unlock(&lp->lp_lock);
                return;
        }
 
-       lp->lpni_notifying = 1;
+       spin_unlock(&lp->lp_lock);
 
-       /*
-        * lp->lpni_notify needs to be protected because it can be set in
-        * lnet_notify_locked().
-        */
-       while (lp->lpni_notify) {
-               alive     = lp->lpni_alive;
-               notifylnd = lp->lpni_notifylnd;
+       if (lp_state & LNET_PEER_PING_FAILED ||
+           pbuf->pb_info.pi_features & LNET_PING_FEAT_RTE_DISABLED) {
+               CDEBUG(D_NET, "Set routes down for gw %s because %s %d\n",
+                      libcfs_nid2str(lp->lp_primary_nid),
+                      lp_state & LNET_PEER_PING_FAILED ? "ping failed" :
+                      "route feature is disabled", lp->lp_ping_error);
+               /* If the ping failed or the peer has routing disabled then
+                * mark the routes served by this peer down
+                */
+               list_for_each_entry(route, &lp->lp_routes, lr_gwlist)
+                       lnet_set_route_aliveness(route, false);
+               return;
+       }
 
-               lp->lpni_notifylnd = 0;
-               lp->lpni_notify    = 0;
+       CDEBUG(D_NET, "Discovery is disabled. Processing reply for gw: %s\n",
+              libcfs_nid2str(lp->lp_primary_nid));
 
-               if (notifylnd && ni->ni_net->net_lnd->lnd_notify != NULL) {
-                       spin_unlock(&lp->lpni_lock);
-                       lnet_net_unlock(lp->lpni_cpt);
+       /*
+        * examine the ping response:
+        * For each NID in the ping response, extract the net
+        * if the net exists on our remote net list then
+        * iterate over the routes on the rnet and if:
+        *      The route's local net is healthy and
+        *      The remote net status is UP, then mark the route up
+        * otherwise mark the route down
+        */
+       for (i = 1; i < pbuf->pb_info.pi_nnis; i++) {
+               net = LNET_NIDNET(pbuf->pb_info.pi_ni[i].ns_nid);
+               rnet = lnet_find_rnet_locked(net);
+               if (!rnet)
+                       continue;
+               list_for_each_entry(route, &rnet->lrn_routes, lr_list) {
+                       /* check if this is the route's gateway */
+                       if (lp->lp_primary_nid !=
+                           route->lr_gateway->lp_primary_nid)
+                               continue;
+
+                       llpn = lnet_peer_get_net_locked(lp, route->lr_lnet);
+                       if (!llpn) {
+                               lnet_set_route_aliveness(route, false);
+                               continue;
+                       }
 
-                       /* A new notification could happen now; I'll handle it
-                        * when control returns to me */
+                       if (!lnet_is_gateway_net_alive(llpn)) {
+                               lnet_set_route_aliveness(route, false);
+                               continue;
+                       }
 
-                       (ni->ni_net->net_lnd->lnd_notify)(ni, lp->lpni_nid,
-                                                         alive);
+                       if (avoid_asym_router_failure &&
+                           pbuf->pb_info.pi_ni[i].ns_status !=
+                               LNET_NI_STATUS_UP) {
+                               net_up = false;
+
+                               /*
+                                * revisit all previous NIDs and check if
+                                * any on the network we're examining is
+                                * up. If at least one is up then we consider
+                                * the route to be alive.
+                                */
+                               for (j = 1; j < i; j++) {
+                                       net2 = LNET_NIDNET(pbuf->pb_info.
+                                                          pi_ni[j].ns_nid);
+                                       if (net2 == net &&
+                                           pbuf->pb_info.pi_ni[j].ns_status ==
+                                               LNET_NI_STATUS_UP)
+                                               net_up = true;
+                               }
+                               if (!net_up) {
+                                       lnet_set_route_aliveness(route, false);
+                                       continue;
+                               }
+                       }
 
-                       lnet_net_lock(lp->lpni_cpt);
-                       spin_lock(&lp->lpni_lock);
+                       lnet_set_route_aliveness(route, true);
                }
        }
+}
 
-       lp->lpni_notifying = 0;
-       spin_unlock(&lp->lpni_lock);
+void
+lnet_router_discovery_complete(struct lnet_peer *lp)
+{
+       struct lnet_peer_ni *lpni = NULL;
+       struct lnet_route *route;
+
+       spin_lock(&lp->lp_lock);
+       lp->lp_state &= ~LNET_PEER_RTR_DISCOVERY;
+       lp->lp_state |= LNET_PEER_RTR_DISCOVERED;
+       lp->lp_alive = lp->lp_dc_error == 0;
+       spin_unlock(&lp->lp_lock);
+
+       /*
+        * Router discovery successful? All peer information would've been
+        * updated already. No need to do any more processing
+        */
+       if (lp->lp_alive)
+               return;
+
+       /*
+        * We do not send messages directly to the remote interfaces
+        * of an LNet router. As such, we rely on the PING response
+        * to determine the up/down status of these interfaces. If
+        * a PING response is not receieved, or some other problem with
+        * discovery occurs that prevents us from getting this status,
+        * we assume all interfaces are down until we're able to
+        * determine otherwise.
+        */
+       CDEBUG(D_NET, "%s: Router discovery failed %d\n",
+              libcfs_nid2str(lp->lp_primary_nid), lp->lp_dc_error);
+       while ((lpni = lnet_get_next_peer_ni_locked(lp, NULL, lpni)) != NULL)
+               lpni->lpni_ns_status = LNET_NI_STATUS_DOWN;
+
+       list_for_each_entry(route, &lp->lp_routes, lr_gwlist)
+               lnet_set_route_aliveness(route, false);
 }
 
 static void
@@ -309,15 +526,15 @@ static void lnet_shuffle_seed(void)
                add_device_randomness(&ni->ni_nid, sizeof(ni->ni_nid));
 
        seeded = 1;
-       return;
 }
 
 /* NB expects LNET_LOCK held */
 static void
 lnet_add_route_to_rnet(struct lnet_remotenet *rnet, struct lnet_route *route)
 {
-       unsigned int len = 0;
+       struct lnet_peer_net *lpn;
        unsigned int offset = 0;
+       unsigned int len = 0;
        struct list_head *e;
 
        lnet_shuffle_seed();
@@ -330,7 +547,7 @@ lnet_add_route_to_rnet(struct lnet_remotenet *rnet, struct lnet_route *route)
         * different nodes are using the same list of routers, they end up
         * preferring different routers.
         */
-       offset = cfs_rand() % (len + 1);
+       offset = prandom_u32_max(len + 1);
        list_for_each(e, &rnet->lrn_routes) {
                if (offset == 0)
                        break;
@@ -341,7 +558,10 @@ lnet_add_route_to_rnet(struct lnet_remotenet *rnet, struct lnet_route *route)
         * force a router check on the gateway to make sure the route is
         * alive
         */
-       route->lr_gateway->lp_rtrcheck_timestamp = 0;
+       list_for_each_entry(lpn, &route->lr_gateway->lp_peer_nets,
+                           lpn_peer_nets) {
+               lpn->lpn_rtrcheck_timestamp = 0;
+       }
 
        the_lnet.ln_remote_nets_version++;
 
@@ -354,7 +574,7 @@ lnet_add_route_to_rnet(struct lnet_remotenet *rnet, struct lnet_route *route)
 
 int
 lnet_add_route(__u32 net, __u32 hops, lnet_nid_t gateway,
-              unsigned int priority)
+              __u32 priority, __u32 sensitivity)
 {
        struct list_head *route_entry;
        struct lnet_remotenet *rnet;
@@ -380,6 +600,13 @@ lnet_add_route(__u32 net, __u32 hops, lnet_nid_t gateway,
        if (lnet_islocalnet(net))
                return -EEXIST;
 
+       if (!lnet_islocalnet(LNET_NIDNET(gateway))) {
+               CERROR("Cannot add route with gateway %s. There is no local interface configured on LNet %s\n",
+                      libcfs_nid2str(gateway),
+                      libcfs_net2str(LNET_NIDNET(gateway)));
+               return -EHOSTUNREACH;
+       }
+
        /* Assume net, route, all new */
        LIBCFS_ALLOC(route, sizeof(*route));
        LIBCFS_ALLOC(rnet, sizeof(*rnet));
@@ -398,6 +625,7 @@ lnet_add_route(__u32 net, __u32 hops, lnet_nid_t gateway,
        /* store the local and remote net that the route represents */
        route->lr_lnet = LNET_NIDNET(gateway);
        route->lr_net = net;
+       route->lr_nid = gateway;
        route->lr_priority = priority;
        route->lr_hops = hops;
 
@@ -456,8 +684,13 @@ lnet_add_route(__u32 net, __u32 hops, lnet_nid_t gateway,
         * to move the routes from the peer that's being deleted to the
         * consolidated peer lp_routes list
         */
-       if (add_route)
+       if (add_route) {
+               gw->lp_health_sensitivity = sensitivity;
                lnet_add_route_to_rnet(rnet2, route);
+               if (lnet_peer_discovery_disabled)
+                       CWARN("Consider turning discovery on to enable full "
+                             "Multi-Rail routing functionality\n");
+       }
 
        /*
         * get rid of the reference on the lpni.
@@ -476,7 +709,7 @@ lnet_add_route(__u32 net, __u32 hops, lnet_nid_t gateway,
                LIBCFS_FREE(rnet, sizeof(*rnet));
 
        /* kick start the monitor thread to handle the added route */
-       wake_up(&the_lnet.ln_mt_waitq);
+       complete(&the_lnet.ln_mt_wait_complete);
 
        return rc;
 }
@@ -514,19 +747,16 @@ lnet_del_route_from_rnet(lnet_nid_t gw_nid, struct list_head *route_list,
 int
 lnet_del_route(__u32 net, lnet_nid_t gw_nid)
 {
-       struct list_head rnet_zombies;
+       LIST_HEAD(rnet_zombies);
        struct lnet_remotenet *rnet;
        struct lnet_remotenet *tmp;
        struct list_head *rn_list;
        struct lnet_peer_ni *lpni;
        struct lnet_route *route;
-       struct list_head zombies;
-       struct lnet_peer *lp;
+       LIST_HEAD(zombies);
+       struct lnet_peer *lp = NULL;
        int i = 0;
 
-       INIT_LIST_HEAD(&rnet_zombies);
-       INIT_LIST_HEAD(&zombies);
-
        CDEBUG(D_NET, "Del route: net %s : gw %s\n",
               libcfs_net2str(net), libcfs_nid2str(gw_nid));
 
@@ -568,6 +798,18 @@ lnet_del_route(__u32 net, lnet_nid_t gw_nid)
        }
 
 delete_zombies:
+       /*
+        * check if there are any routes remaining on the gateway
+        * If there are no more routes make sure to set the peer's
+        * lp_disc_net_id to 0 (invalid), in case we add more routes in
+        * the future on that gateway, then we start our discovery process
+        * from scratch
+        */
+       if (lpni) {
+               if (list_empty(&lp->lp_routes))
+                       lp->lp_disc_net_id = 0;
+       }
+
        lnet_net_unlock(LNET_LOCK_EX);
 
        while (!list_empty(&zombies)) {
@@ -626,15 +868,15 @@ int lnet_get_rtr_pool_cfg(int cpt, struct lnet_ioctl_pool_cfg *pool_cfg)
 
 int
 lnet_get_route(int idx, __u32 *net, __u32 *hops,
-              lnet_nid_t *gateway, __u32 *alive, __u32 *priority)
+              lnet_nid_t *gateway, __u32 *alive, __u32 *priority, __u32 *sensitivity)
 {
-       struct list_head *e1;
-       struct list_head *e2;
        struct lnet_remotenet *rnet;
-       struct lnet_route        *route;
-       int               cpt;
-       int               i;
        struct list_head *rn_list;
+       struct lnet_route *route;
+       struct list_head *e1;
+       struct list_head *e2;
+       int cpt;
+       int i;
 
        cpt = lnet_net_lock_current();
 
@@ -649,9 +891,11 @@ lnet_get_route(int idx, __u32 *net, __u32 *hops,
 
                                if (idx-- == 0) {
                                        *net      = rnet->lrn_net;
+                                       *gateway  = route->lr_nid;
                                        *hops     = route->lr_hops;
                                        *priority = route->lr_priority;
-                                       *gateway  = route->lr_gateway->lp_primary_nid;
+                                       *sensitivity = route->lr_gateway->
+                                               lp_health_sensitivity;
                                        *alive    = lnet_is_route_alive(route);
                                        lnet_net_unlock(cpt);
                                        return 0;
@@ -664,89 +908,6 @@ lnet_get_route(int idx, __u32 *net, __u32 *hops,
        return -ENOENT;
 }
 
-void
-lnet_swap_pinginfo(struct lnet_ping_buffer *pbuf)
-{
-       struct lnet_ni_status *stat;
-       int nnis;
-       int i;
-
-       __swab32s(&pbuf->pb_info.pi_magic);
-       __swab32s(&pbuf->pb_info.pi_features);
-       __swab32s(&pbuf->pb_info.pi_pid);
-       __swab32s(&pbuf->pb_info.pi_nnis);
-       nnis = pbuf->pb_info.pi_nnis;
-       if (nnis > pbuf->pb_nnis)
-               nnis = pbuf->pb_nnis;
-       for (i = 0; i < nnis; i++) {
-               stat = &pbuf->pb_info.pi_ni[i];
-               __swab64s(&stat->ns_nid);
-               __swab32s(&stat->ns_status);
-       }
-       return;
-}
-
-/**
- * TODO: re-implement
- */
-static void
-lnet_parse_rc_info(struct lnet_rc_data *rcd)
-{
-       rcd = rcd;
-}
-
-static void
-lnet_router_checker_event(struct lnet_event *event)
-{
-       struct lnet_rc_data *rcd = event->md.user_ptr;
-       struct lnet_peer_ni *lp;
-
-       LASSERT(rcd != NULL);
-
-       if (event->unlinked) {
-               LNetInvalidateMDHandle(&rcd->rcd_mdh);
-               return;
-       }
-
-       LASSERT(event->type == LNET_EVENT_SEND ||
-               event->type == LNET_EVENT_REPLY);
-
-       lp = rcd->rcd_gateway;
-       LASSERT(lp != NULL);
-
-        /* NB: it's called with holding lnet_res_lock, we have a few
-         * places need to hold both locks at the same time, please take
-         * care of lock ordering */
-       lnet_net_lock(lp->lpni_cpt);
-       if (!lnet_isrouter(lp) || lp->lpni_rcd != rcd) {
-               /* ignore if no longer a router or rcd is replaced */
-               goto out;
-       }
-
-       if (event->type == LNET_EVENT_SEND) {
-               if (event->status == 0)
-                       goto out;
-       }
-
-       /* LNET_EVENT_REPLY */
-       /* A successful REPLY means the router is up.  If _any_ comms
-        * to the router fail I assume it's down (this will happen if
-        * we ping alive routers to try to detect router death before
-        * apps get burned). */
-
-       lnet_notify_locked(lp, 1, !event->status, ktime_get_seconds());
-       /* The router checker will wake up very shortly and do the
-        * actual notification.
-        * XXX If 'lp' stops being a router before then, it will still
-        * have the notification pending!!! */
-
-       if (avoid_asym_router_failure && event->status == 0)
-               lnet_parse_rc_info(rcd);
-
- out:
-       lnet_net_unlock(lp->lpni_cpt);
-}
-
 static void
 lnet_wait_known_routerstate(void)
 {
@@ -766,7 +927,7 @@ lnet_wait_known_routerstate(void)
 
                        spin_lock(&rtr->lp_lock);
 
-                       if ((rtr->lp_state & LNET_PEER_DISCOVERED) == 0) {
+                       if ((rtr->lp_state & LNET_PEER_RTR_DISCOVERED) == 0) {
                                all_known = 0;
                                spin_unlock(&rtr->lp_lock);
                                break;
@@ -784,88 +945,65 @@ lnet_wait_known_routerstate(void)
        }
 }
 
-/* TODO: reimplement */
-void
-lnet_router_ni_update_locked(struct lnet_peer_ni *gw, __u32 net)
+static inline bool
+lnet_net_set_status_locked(struct lnet_net *net, __u32 status)
 {
-       struct lnet_route *rte;
-       struct lnet_peer *lp;
+       struct lnet_ni *ni;
+       bool update = false;
 
-       if ((gw->lpni_ping_feats & LNET_PING_FEAT_NI_STATUS) != 0)
-               lp = gw->lpni_peer_net->lpn_peer;
-       else
-               return;
-
-       list_for_each_entry(rte, &lp->lp_routes, lr_gwlist) {
-               if (rte->lr_net == net) {
-                       rte->lr_downis = 0;
-                       break;
+       list_for_each_entry(ni, &net->net_ni_list, ni_netlist) {
+               lnet_ni_lock(ni);
+               if (ni->ni_status &&
+                   ni->ni_status->ns_status != status) {
+                   ni->ni_status->ns_status = status;
+                   update = true;
                }
+               lnet_ni_unlock(ni);
        }
+
+       return update;
 }
 
-static void
+static bool
 lnet_update_ni_status_locked(void)
 {
-       struct lnet_ni *ni = NULL;
+       struct lnet_net *net;
+       bool push = false;
        time64_t now;
        time64_t timeout;
 
        LASSERT(the_lnet.ln_routing);
 
-       timeout = router_ping_timeout +
-                 MAX(live_router_check_interval, dead_router_check_interval);
+       timeout = router_ping_timeout + alive_router_check_interval;
 
        now = ktime_get_real_seconds();
-       while ((ni = lnet_get_next_ni_locked(NULL, ni))) {
-               if (ni->ni_net->net_lnd->lnd_type == LOLND)
+       list_for_each_entry(net, &the_lnet.ln_nets, net_list) {
+               if (net->net_lnd->lnd_type == LOLND)
                        continue;
 
-               if (now < ni->ni_last_alive + timeout)
+               if (now < net->net_last_alive + timeout)
                        continue;
 
-               lnet_ni_lock(ni);
+               spin_lock(&net->net_lock);
                /* re-check with lock */
-               if (now < ni->ni_last_alive + timeout) {
-                       lnet_ni_unlock(ni);
+               if (now < net->net_last_alive + timeout) {
+                       spin_unlock(&net->net_lock);
                        continue;
                }
+               spin_unlock(&net->net_lock);
 
-               LASSERT(ni->ni_status != NULL);
-
-               if (ni->ni_status->ns_status != LNET_NI_STATUS_DOWN) {
-                       CDEBUG(D_NET, "NI(%s:%lld) status changed to down\n",
-                              libcfs_nid2str(ni->ni_nid), timeout);
-                       /* NB: so far, this is the only place to set
-                        * NI status to "down" */
-                       ni->ni_status->ns_status = LNET_NI_STATUS_DOWN;
-               }
-               lnet_ni_unlock(ni);
-       }
-}
-
-int lnet_router_pre_mt_start(void)
-{
-       int rc;
-
-       if (check_routers_before_use &&
-           dead_router_check_interval <= 0) {
-               LCONSOLE_ERROR_MSG(0x10a, "'dead_router_check_interval' must be"
-                                  " set if 'check_routers_before_use' is set"
-                                  "\n");
-               return -EINVAL;
-       }
-
-       rc = LNetEQAlloc(0, lnet_router_checker_event, &the_lnet.ln_rc_eqh);
-       if (rc != 0) {
-               CERROR("Can't allocate EQ(0): %d\n", rc);
-               return -ENOMEM;
+               /*
+                * if the net didn't receive any traffic for past the
+                * timeout on any of its constituent NIs, then mark all
+                * the NIs down.
+                */
+               push = lnet_net_set_status_locked(net, LNET_NI_STATUS_DOWN);
        }
 
-       return 0;
+       return push;
 }
 
-void lnet_router_post_mt_start(void)
+void lnet_wait_router_start(void)
 {
        if (check_routers_before_use) {
                /* Note that a helpful side-effect of pinging all known routers
@@ -875,22 +1013,6 @@ void lnet_router_post_mt_start(void)
        }
 }
 
-void
-lnet_router_cleanup(void)
-{
-       int rc;
-
-       rc = LNetEQFree(the_lnet.ln_rc_eqh);
-       LASSERT(rc == 0);
-       return;
-}
-
-void
-lnet_prune_rc_data(int wait_unlink)
-{
-       wait_unlink = wait_unlink;
-}
-
 /*
  * This function is called from the monitor thread to check if there are
  * any active routers that need to be checked.
@@ -898,31 +1020,30 @@ lnet_prune_rc_data(int wait_unlink)
 inline bool
 lnet_router_checker_active(void)
 {
-       if (the_lnet.ln_mt_state != LNET_MT_STATE_RUNNING)
-               return true;
-
        /* Router Checker thread needs to run when routing is enabled in
         * order to call lnet_update_ni_status_locked() */
        if (the_lnet.ln_routing)
                return true;
 
-       /* if there are routers that need to be cleaned up then do so */
-       if (!list_empty(&the_lnet.ln_rcd_deathrow) ||
-           !list_empty(&the_lnet.ln_rcd_zombie))
-               return true;
-
        return !list_empty(&the_lnet.ln_routers) &&
-               (live_router_check_interval > 0 ||
-                dead_router_check_interval > 0);
+               alive_router_check_interval > 0;
 }
 
 void
 lnet_check_routers(void)
 {
-       struct lnet_peer *rtr;
+       struct lnet_peer_net *first_lpn = NULL;
+       struct lnet_peer_net *lpn;
+       struct lnet_peer_ni *lpni;
        struct list_head *entry;
-       __u64   version;
-       int     cpt;
+       struct lnet_peer *rtr;
+       bool push = false;
+       bool found_lpn;
+       __u64 version;
+       __u32 net_id;
+       time64_t now;
+       int cpt;
+       int rc;
 
        cpt = lnet_net_lock_current();
 rescan:
@@ -932,7 +1053,80 @@ rescan:
                rtr = list_entry(entry, struct lnet_peer,
                                 lp_rtr_list);
 
-               /* TODO use discovery to determine if router is alive */
+               now = ktime_get_real_seconds();
+
+               /*
+                * only discover the router if we've passed
+                * alive_router_check_interval seconds. Some of the router
+                * interfaces could be down and in that case they would be
+                * undergoing recovery separately from this discovery.
+                */
+               /* find next peer net which is also local */
+               net_id = rtr->lp_disc_net_id;
+               do {
+                       lpn = lnet_get_next_peer_net_locked(rtr, net_id);
+                       if (!lpn) {
+                               CERROR("gateway %s has no networks\n",
+                               libcfs_nid2str(rtr->lp_primary_nid));
+                               break;
+                       }
+                       if (first_lpn == lpn)
+                               break;
+                       if (!first_lpn)
+                               first_lpn = lpn;
+                       found_lpn = lnet_islocalnet_locked(lpn->lpn_net_id);
+                       net_id = lpn->lpn_net_id;
+               } while (!found_lpn);
+
+               if (!found_lpn || !lpn) {
+                       CERROR("no local network found for gateway %s\n",
+                              libcfs_nid2str(rtr->lp_primary_nid));
+                       continue;
+               }
+
+               if (now - lpn->lpn_rtrcheck_timestamp <
+                   alive_router_check_interval / lnet_current_net_count)
+                      continue;
+
+               /*
+                * If we're currently discovering the peer then don't
+                * issue another discovery
+                */
+               spin_lock(&rtr->lp_lock);
+               if (rtr->lp_state & LNET_PEER_RTR_DISCOVERY) {
+                       spin_unlock(&rtr->lp_lock);
+                       continue;
+               }
+               /* make sure we actively discover the router */
+               rtr->lp_state &= ~LNET_PEER_NIDS_UPTODATE;
+               rtr->lp_state |= LNET_PEER_RTR_DISCOVERY;
+               spin_unlock(&rtr->lp_lock);
+
+               /* find the peer_ni associated with the primary NID */
+               lpni = lnet_peer_get_ni_locked(rtr, rtr->lp_primary_nid);
+               if (!lpni) {
+                       CDEBUG(D_NET, "Expected to find an lpni for %s, but non found\n",
+                              libcfs_nid2str(rtr->lp_primary_nid));
+                       continue;
+               }
+               lnet_peer_ni_addref_locked(lpni);
+
+               /* specify the net to use */
+               rtr->lp_disc_net_id = lpn->lpn_net_id;
+
+               /* discover the router */
+               CDEBUG(D_NET, "discover %s, cpt = %d\n",
+                      libcfs_nid2str(lpni->lpni_nid), cpt);
+               rc = lnet_discover_peer_locked(lpni, cpt, false);
+
+               /* decrement ref count acquired by find_peer_ni_locked() */
+               lnet_peer_ni_decref_locked(lpni);
+
+               if (!rc)
+                       lpn->lpn_rtrcheck_timestamp = now;
+               else
+                       CERROR("Failed to discover router %s\n",
+                              libcfs_nid2str(rtr->lp_primary_nid));
 
                /* NB dropped lock */
                if (version != the_lnet.ln_routers_version) {
@@ -942,11 +1136,13 @@ rescan:
        }
 
        if (the_lnet.ln_routing)
-               lnet_update_ni_status_locked();
+               push = lnet_update_ni_status_locked();
 
        lnet_net_unlock(cpt);
 
-       lnet_prune_rc_data(0); /* don't wait for UNLINK */
+       /* if the status of the ni changed update the peers */
+       if (push)
+               lnet_push_update_to_peers(1);
 }
 
 void
@@ -999,13 +1195,11 @@ lnet_rtrpool_free_bufs(struct lnet_rtrbufpool *rbp, int cpt)
 {
        int npages = rbp->rbp_npages;
        struct lnet_rtrbuf *rb;
-       struct list_head tmp;
+       LIST_HEAD(tmp);
 
        if (rbp->rbp_nbuffers == 0) /* not initialized or already freed */
                return;
 
-       INIT_LIST_HEAD(&tmp);
-
        lnet_net_lock(cpt);
        list_splice_init(&rbp->rbp_msgs, &tmp);
        lnet_drop_routed_msgs_locked(&tmp, cpt);
@@ -1026,7 +1220,7 @@ lnet_rtrpool_free_bufs(struct lnet_rtrbufpool *rbp, int cpt)
 static int
 lnet_rtrpool_adjust_bufs(struct lnet_rtrbufpool *rbp, int nbufs, int cpt)
 {
-       struct list_head rb_list;
+       LIST_HEAD(rb_list);
        struct lnet_rtrbuf *rb;
        int             num_rb;
        int             num_buffers = 0;
@@ -1054,8 +1248,6 @@ lnet_rtrpool_adjust_bufs(struct lnet_rtrbufpool *rbp, int nbufs, int cpt)
        rbp->rbp_req_nbuffers = nbufs;
        lnet_net_unlock(cpt);
 
-       INIT_LIST_HEAD(&rb_list);
-
        /* allocate the buffers on a local list first.  If all buffers are
         * allocated successfully then join this list to the rbp buffer
         * list.  If not then free all allocated buffers. */
@@ -1262,7 +1454,7 @@ lnet_rtrpools_alloc(int im_a_router)
        lnet_net_lock(LNET_LOCK_EX);
        the_lnet.ln_routing = 1;
        lnet_net_unlock(LNET_LOCK_EX);
-       wake_up(&the_lnet.ln_mt_waitq);
+       complete(&the_lnet.ln_mt_wait_complete);
        return 0;
 
  failed:
@@ -1354,6 +1546,10 @@ lnet_rtrpools_enable(void)
                ~LNET_PING_FEAT_RTE_DISABLED;
        lnet_net_unlock(LNET_LOCK_EX);
 
+       if (lnet_peer_discovery_disabled)
+               CWARN("Consider turning discovery on to enable full "
+                     "Multi-Rail routing functionality\n");
+
        return rc;
 }
 
@@ -1375,12 +1571,29 @@ lnet_rtrpools_disable(void)
        lnet_rtrpools_free(1);
 }
 
+static inline void
+lnet_notify_peer_down(struct lnet_ni *ni, lnet_nid_t nid)
+{
+       if (ni->ni_net->net_lnd->lnd_notify_peer_down != NULL)
+               (ni->ni_net->net_lnd->lnd_notify_peer_down)(nid);
+}
+
+/*
+ * ni: local NI used to communicate with the peer
+ * nid: peer NID
+ * alive: true if peer is alive, false otherwise
+ * reset: reset health value. This is requested by the LND.
+ * when: notificaiton time.
+ */
 int
-lnet_notify(struct lnet_ni *ni, lnet_nid_t nid, int alive, time64_t when)
+lnet_notify(struct lnet_ni *ni, lnet_nid_t nid, bool alive, bool reset,
+           time64_t when)
 {
-       struct lnet_peer_ni *lp = NULL;
+       struct lnet_peer_ni *lpni = NULL;
+       struct lnet_route *route;
+       struct lnet_peer *lp;
        time64_t now = ktime_get_seconds();
-       int cpt = lnet_cpt_of_nid(nid, ni);
+       int cpt;
 
        LASSERT (!in_interrupt ());
 
@@ -1412,48 +1625,50 @@ lnet_notify(struct lnet_ni *ni, lnet_nid_t nid, int alive, time64_t when)
                return 0;
        }
 
-       lnet_net_lock(cpt);
+       /* must lock 0 since this is used for synchronization */
+       lnet_net_lock(0);
 
        if (the_lnet.ln_state != LNET_STATE_RUNNING) {
-               lnet_net_unlock(cpt);
+               lnet_net_unlock(0);
                return -ESHUTDOWN;
        }
 
-       lp = lnet_find_peer_ni_locked(nid);
-       if (lp == NULL) {
+       lpni = lnet_find_peer_ni_locked(nid);
+       if (lpni == NULL) {
                /* nid not found */
-               lnet_net_unlock(cpt);
+               lnet_net_unlock(0);
                CDEBUG(D_NET, "%s not found\n", libcfs_nid2str(nid));
                return 0;
        }
 
-       /*
-        * It is possible for this function to be called for the same peer
-        * but with different NIs. We want to synchronize the notification
-        * between the different calls. So we will use the lpni_cpt to
-        * grab the net lock.
-        */
-       if (lp->lpni_cpt != cpt) {
-               lnet_net_unlock(cpt);
-               cpt = lp->lpni_cpt;
-               lnet_net_lock(cpt);
+       if (alive) {
+               if (reset)
+                       lnet_set_healthv(&lpni->lpni_healthv,
+                                        LNET_MAX_HEALTH_VALUE);
+               else
+                       lnet_inc_healthv(&lpni->lpni_healthv);
+       } else {
+               lnet_handle_remote_failure_locked(lpni);
        }
 
-       /* We can't fully trust LND on reporting exact peer last_alive
-        * if he notifies us about dead peer. For example ksocklnd can
-        * call us with when == _time_when_the_node_was_booted_ if
-        * no connections were successfully established */
-       if (ni != NULL && !alive && when < lp->lpni_last_alive)
-               when = lp->lpni_last_alive;
+       /* recalculate aliveness */
+       alive = lnet_is_peer_ni_alive(lpni);
+       lnet_net_unlock(0);
 
-       lnet_notify_locked(lp, ni == NULL, alive, when);
-
-       if (ni != NULL)
-               lnet_ni_notify_locked(ni, lp);
-
-       lnet_peer_ni_decref_locked(lp);
+       if (ni != NULL && !alive)
+               lnet_notify_peer_down(ni, lpni->lpni_nid);
 
+       cpt = lpni->lpni_cpt;
+       lnet_net_lock(cpt);
+       lnet_peer_ni_decref_locked(lpni);
+       if (lpni && lpni->lpni_peer_net && lpni->lpni_peer_net->lpn_peer) {
+               lp = lpni->lpni_peer_net->lpn_peer;
+               lp->lp_alive = alive;
+               list_for_each_entry(route, &lp->lp_routes, lr_gwlist)
+                       lnet_set_route_aliveness(route, alive);
+       }
        lnet_net_unlock(cpt);
+
        return 0;
 }
 EXPORT_SYMBOL(lnet_notify);