tipc: make bearer packet filtering generic

In commit 5b7066c ("tipc: stricter filtering of packets in bearer
layer") we introduced a method of filtering out messages while a bearer
is being reset, to avoid that links may be re-created and come back in
working state while we are still in the process of shutting them down.

This solution works well, but is limited to only work with L2 media, which
is insufficient with the increasing use of UDP as carrier media.

We now replace this solution with a more generic one, by introducing a
new flag "up" in the generic struct tipc_bearer. This field will be set
and reset at the same locations as with the previous solution, while
the packet filtering is moved to the generic code for the sending side.
On the receiving side, the filtering is still done in media specific
code, but now including the UDP bearer.

Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/bearer.c

@@ -56,6 +56,13 @@ static struct tipc_media * const media_info_array[] = {
 	NULL
 };
 
+static struct tipc_bearer *bearer_get(struct net *net, int bearer_id)
+{
+	struct tipc_net *tn = tipc_net(net);
+
+	return rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
+}
+
 static void bearer_disable(struct net *net, struct tipc_bearer *b);
 
 /**
@@ -323,6 +330,7 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 	b->domain = disc_domain;
 	b->net_plane = bearer_id + 'A';
 	b->priority = priority;
+	test_and_set_bit_lock(0, &b->up);
 
 	res = tipc_disc_create(net, b, &b->bcast_addr, &skb);
 	if (res) {
@@ -360,15 +368,24 @@ static int tipc_reset_bearer(struct net *net, struct tipc_bearer *b)
  */
 void tipc_bearer_reset_all(struct net *net)
 {
-	struct tipc_net *tn = tipc_net(net);
 	struct tipc_bearer *b;
 	int i;
 
 	for (i = 0; i < MAX_BEARERS; i++) {
-		b = rcu_dereference_rtnl(tn->bearer_list[i]);
+		b = bearer_get(net, i);
+		if (b)
+			clear_bit_unlock(0, &b->up);
+	}
+	for (i = 0; i < MAX_BEARERS; i++) {
+		b = bearer_get(net, i);
 		if (b)
 			tipc_reset_bearer(net, b);
 	}
+	for (i = 0; i < MAX_BEARERS; i++) {
+		b = bearer_get(net, i);
+		if (b)
+			test_and_set_bit_lock(0, &b->up);
+	}
 }
 
 /**
@@ -382,8 +399,9 @@ static void bearer_disable(struct net *net, struct tipc_bearer *b)
 	int bearer_id = b->identity;
 
 	pr_info("Disabling bearer <%s>\n", b->name);
-	b->media->disable_media(b);
+	clear_bit_unlock(0, &b->up);
 	tipc_node_delete_links(net, bearer_id);
+	b->media->disable_media(b);
 	RCU_INIT_POINTER(b->media_ptr, NULL);
 	if (b->link_req)
 		tipc_disc_delete(b->link_req);
@@ -440,32 +458,23 @@ int tipc_l2_send_msg(struct net *net, struct sk_buff *skb,
 {
 	struct net_device *dev;
 	int delta;
-	void *tipc_ptr;
 
 	dev = (struct net_device *)rcu_dereference_rtnl(b->media_ptr);
 	if (!dev)
 		return 0;
 
-	/* Send RESET message even if bearer is detached from device */
-	tipc_ptr = rcu_dereference_rtnl(dev->tipc_ptr);
-	if (unlikely(!tipc_ptr && !msg_is_reset(buf_msg(skb))))
-		goto drop;
-
-	delta = dev->hard_header_len - skb_headroom(skb);
-	if ((delta > 0) &&
-	    pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC))
-		goto drop;
-
+	delta = SKB_DATA_ALIGN(dev->hard_header_len - skb_headroom(skb));
+	if ((delta > 0) && pskb_expand_head(skb, delta, 0, GFP_ATOMIC)) {
+		kfree_skb(skb);
+		return 0;
+	}
 	skb_reset_network_header(skb);
 	skb->dev = dev;
 	skb->protocol = htons(ETH_P_TIPC);
 	dev_hard_header(skb, dev, ETH_P_TIPC, dest->value,
 			dev->dev_addr, skb->len);
 	dev_queue_xmit(skb);
 	return 0;
-drop:
-	kfree_skb(skb);
-	return 0;
 }
 
 int tipc_bearer_mtu(struct net *net, u32 bearer_id)
@@ -487,12 +496,12 @@ void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
 			  struct sk_buff *skb,
 			  struct tipc_media_addr *dest)
 {
-	struct tipc_net *tn = tipc_net(net);
+	struct tipc_msg *hdr = buf_msg(skb);
 	struct tipc_bearer *b;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
-	if (likely(b))
+	b = bearer_get(net, bearer_id);
+	if (likely(b && (test_bit(0, &b->up) || msg_is_reset(hdr))))
 		b->media->send_msg(net, skb, b, dest);
 	else
 		kfree_skb(skb);
@@ -505,20 +514,22 @@ void tipc_bearer_xmit(struct net *net, u32 bearer_id,
 		      struct sk_buff_head *xmitq,
 		      struct tipc_media_addr *dst)
 {
-	struct tipc_net *tn = net_generic(net, tipc_net_id);
 	struct tipc_bearer *b;
 	struct sk_buff *skb, *tmp;
 
 	if (skb_queue_empty(xmitq))
 		return;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
+	b = bearer_get(net, bearer_id);
 	if (unlikely(!b))
 		__skb_queue_purge(xmitq);
 	skb_queue_walk_safe(xmitq, skb, tmp) {
 		__skb_dequeue(xmitq);
-		b->media->send_msg(net, skb, b, dst);
+		if (likely(test_bit(0, &b->up) || msg_is_reset(buf_msg(skb))))
+			b->media->send_msg(net, skb, b, dst);
+		else
+			kfree(skb);
 	}
 	rcu_read_unlock();
 }
@@ -535,8 +546,8 @@ void tipc_bearer_bc_xmit(struct net *net, u32 bearer_id,
 	struct tipc_msg *hdr;
 
 	rcu_read_lock();
-	b = rcu_dereference_rtnl(tn->bearer_list[bearer_id]);
-	if (unlikely(!b))
+	b = bearer_get(net, bearer_id);
+	if (unlikely(!b || !test_bit(0, &b->up)))
 		__skb_queue_purge(xmitq);
 	skb_queue_walk_safe(xmitq, skb, tmp) {
 		hdr = buf_msg(skb);
@@ -566,7 +577,8 @@ static int tipc_l2_rcv_msg(struct sk_buff *skb, struct net_device *dev,
 
 	rcu_read_lock();
 	b = rcu_dereference_rtnl(dev->tipc_ptr);
-	if (likely(b && (skb->pkt_type <= PACKET_BROADCAST))) {
+	if (likely(b && test_bit(0, &b->up) &&
+		   (skb->pkt_type <= PACKET_BROADCAST))) {
 		skb->next = NULL;
 		tipc_rcv(dev_net(dev), skb, b);
 		rcu_read_unlock();
@@ -591,18 +603,9 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct net *net = dev_net(dev);
-	struct tipc_net *tn = tipc_net(net);
 	struct tipc_bearer *b;
-	int i;
 
 	b = rtnl_dereference(dev->tipc_ptr);
-	if (!b) {
-		for (i = 0; i < MAX_BEARERS; b = NULL, i++) {
-			b = rtnl_dereference(tn->bearer_list[i]);
-			if (b && (b->media_ptr == dev))
-				break;
-		}
-	}
 	if (!b)
 		return NOTIFY_DONE;
 
@@ -613,11 +616,10 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
 		if (netif_carrier_ok(dev))
 			break;
 	case NETDEV_UP:
-		rcu_assign_pointer(dev->tipc_ptr, b);
+		test_and_set_bit_lock(0, &b->up);
 		break;
 	case NETDEV_GOING_DOWN:
-		RCU_INIT_POINTER(dev->tipc_ptr, NULL);
-		synchronize_net();
+		clear_bit_unlock(0, &b->up);
 		tipc_reset_bearer(net, b);
 		break;
 	case NETDEV_CHANGEMTU:

net/tipc/bearer.h

@@ -150,6 +150,7 @@ struct tipc_bearer {
 	u32 identity;
 	struct tipc_link_req *link_req;
 	char net_plane;
+	unsigned long up;
 };
 
 struct tipc_bearer_names {

net/tipc/udp_media.c

@@ -224,7 +224,7 @@ static int tipc_udp_recv(struct sock *sk, struct sk_buff *skb)
 	rcu_read_lock();
 	b = rcu_dereference_rtnl(ub->bearer);
 
-	if (b) {
+	if (b && test_bit(0, &b->up)) {
 		tipc_rcv(sock_net(sk), skb, b);
 		rcu_read_unlock();
 		return 0;