net: dsa: make dp->bridge_num one-based

I have seen too many bugs already due to the fact that we must encode an
invalid dp->bridge_num as a negative value, because the natural tendency
is to check that invalid value using (!dp->bridge_num). Latest example
can be seen in commit 1bec0f05062c ("net: dsa: fix bridge_num not
getting cleared after ports leaving the bridge").

Convert the existing users to assume that dp->bridge_num == 0 is the
encoding for invalid, and valid bridge numbers start from 1.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

5 files changed, 29 insertions, 25 deletions

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index 826957b6442b..9606e56710a5 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -141,23 +141,23 @@ static int dsa_bridge_num_find(const struct net_device *bridge_dev)
 	 */
 	list_for_each_entry(dst, &dsa_tree_list, list)
 		list_for_each_entry(dp, &dst->ports, list)
-			if (dp->bridge_dev == bridge_dev &&
-			    dp->bridge_num != -1)
+			if (dp->bridge_dev == bridge_dev && dp->bridge_num)
 				return dp->bridge_num;
 
-	return -1;
+	return 0;
 }
 
-int dsa_bridge_num_get(const struct net_device *bridge_dev, int max)
+unsigned int dsa_bridge_num_get(const struct net_device *bridge_dev, int max)
 {
-	int bridge_num = dsa_bridge_num_find(bridge_dev);
+	unsigned int bridge_num = dsa_bridge_num_find(bridge_dev);
 
-	if (bridge_num < 0) {
+	if (!bridge_num) {
 		/* First port that offloads TX forwarding for this bridge */
-		bridge_num = find_first_zero_bit(&dsa_fwd_offloading_bridges,
-						 DSA_MAX_NUM_OFFLOADING_BRIDGES);
+		bridge_num = find_next_zero_bit(&dsa_fwd_offloading_bridges,
+						DSA_MAX_NUM_OFFLOADING_BRIDGES,
+						1);
 		if (bridge_num >= max)
-			return -1;
+			return 0;
 
 		set_bit(bridge_num, &dsa_fwd_offloading_bridges);
 	}
@@ -165,12 +165,13 @@ int dsa_bridge_num_get(const struct net_device *bridge_dev, int max)
 	return bridge_num;
 }
 
-void dsa_bridge_num_put(const struct net_device *bridge_dev, int bridge_num)
+void dsa_bridge_num_put(const struct net_device *bridge_dev,
+			unsigned int bridge_num)
 {
 	/* Check if the bridge is still in use, otherwise it is time
 	 * to clean it up so we can reuse this bridge_num later.
 	 */
-	if (dsa_bridge_num_find(bridge_dev) < 0)
+	if (!dsa_bridge_num_find(bridge_dev))
 		clear_bit(bridge_num, &dsa_fwd_offloading_bridges);
 }
 
@@ -1184,7 +1185,6 @@ static struct dsa_port *dsa_port_touch(struct dsa_switch *ds, int index)
 
 	dp->ds = ds;
 	dp->index = index;
-	dp->bridge_num = -1;
 
 	INIT_LIST_HEAD(&dp->list);
 	list_add_tail(&dp->list, &dst->ports);
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 3fb2c37c9b88..70c4a5b36a8b 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -546,8 +546,9 @@ int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
 			      struct net_device *master,
 			      const struct dsa_device_ops *tag_ops,
 			      const struct dsa_device_ops *old_tag_ops);
-int dsa_bridge_num_get(const struct net_device *bridge_dev, int max);
-void dsa_bridge_num_put(const struct net_device *bridge_dev, int bridge_num);
+unsigned int dsa_bridge_num_get(const struct net_device *bridge_dev, int max);
+void dsa_bridge_num_put(const struct net_device *bridge_dev,
+			unsigned int bridge_num);
 
 /* tag_8021q.c */
 int dsa_tag_8021q_bridge_join(struct dsa_switch *ds,
diff --git a/net/dsa/port.c b/net/dsa/port.c
index 6d5ebe61280b..9a77bd1373e2 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -273,14 +273,14 @@ static void dsa_port_switchdev_unsync_attrs(struct dsa_port *dp)
 static void dsa_port_bridge_tx_fwd_unoffload(struct dsa_port *dp,
 					     struct net_device *bridge_dev)
 {
-	int bridge_num = dp->bridge_num;
+	unsigned int bridge_num = dp->bridge_num;
 	struct dsa_switch *ds = dp->ds;
 
 	/* No bridge TX forwarding offload => do nothing */
-	if (!ds->ops->port_bridge_tx_fwd_unoffload || dp->bridge_num == -1)
+	if (!ds->ops->port_bridge_tx_fwd_unoffload || !dp->bridge_num)
 		return;
 
-	dp->bridge_num = -1;
+	dp->bridge_num = 0;
 
 	dsa_bridge_num_put(bridge_dev, bridge_num);
 
@@ -295,14 +295,15 @@ static bool dsa_port_bridge_tx_fwd_offload(struct dsa_port *dp,
 					   struct net_device *bridge_dev)
 {
 	struct dsa_switch *ds = dp->ds;
-	int bridge_num, err;
+	unsigned int bridge_num;
+	int err;
 
 	if (!ds->ops->port_bridge_tx_fwd_offload)
 		return false;
 
 	bridge_num = dsa_bridge_num_get(bridge_dev,
 					ds->num_fwd_offloading_bridges);
-	if (bridge_num < 0)
+	if (!bridge_num)
 		return false;
 
 	dp->bridge_num = bridge_num;
diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 72cac2c0af7b..df59f16436a5 100644
--- a/net/dsa/tag_8021q.c
+++ b/net/dsa/tag_8021q.c
@@ -67,10 +67,12 @@
 #define DSA_8021Q_PORT(x)		(((x) << DSA_8021Q_PORT_SHIFT) & \
 						 DSA_8021Q_PORT_MASK)
 
-u16 dsa_8021q_bridge_tx_fwd_offload_vid(int bridge_num)
+u16 dsa_8021q_bridge_tx_fwd_offload_vid(unsigned int bridge_num)
 {
-	/* The VBID value of 0 is reserved for precise TX */
-	return DSA_8021Q_DIR_TX | DSA_8021Q_VBID(bridge_num + 1);
+	/* The VBID value of 0 is reserved for precise TX, but it is also
+	 * reserved/invalid for the bridge_num, so all is well.
+	 */
+	return DSA_8021Q_DIR_TX | DSA_8021Q_VBID(bridge_num);
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_bridge_tx_fwd_offload_vid);
 
@@ -409,7 +411,7 @@ int dsa_tag_8021q_bridge_leave(struct dsa_switch *ds,
 
 int dsa_tag_8021q_bridge_tx_fwd_offload(struct dsa_switch *ds, int port,
 					struct net_device *br,
-					int bridge_num)
+					unsigned int bridge_num)
 {
 	u16 tx_vid = dsa_8021q_bridge_tx_fwd_offload_vid(bridge_num);
 
@@ -420,7 +422,7 @@ EXPORT_SYMBOL_GPL(dsa_tag_8021q_bridge_tx_fwd_offload);
 
 void dsa_tag_8021q_bridge_tx_fwd_unoffload(struct dsa_switch *ds, int port,
 					   struct net_device *br,
-					   int bridge_num)
+					   unsigned int bridge_num)
 {
 	u16 tx_vid = dsa_8021q_bridge_tx_fwd_offload_vid(bridge_num);
 
diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index b3da4b2ea11c..a7d70ae7cc97 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -140,7 +140,7 @@ static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
 		 * packets on behalf of a virtual switch device with an index
 		 * past the physical switches.
 		 */
-		tag_dev = dst->last_switch + 1 + dp->bridge_num;
+		tag_dev = dst->last_switch + dp->bridge_num;
 		tag_port = 0;
 	} else {
 		cmd = DSA_CMD_FROM_CPU;