net: dsa: keep the bridge_dev and bridge_num as part of the same structure

The main desire behind this is to provide coherent bridge information to
the fast path without locking.

For example, right now we set dp->bridge_dev and dp->bridge_num from
separate code paths, it is theoretically possible for a packet
transmission to read these two port properties consecutively and find a
bridge number which does not correspond with the bridge device.

Another desire is to start passing more complex bridge information to
dsa_switch_ops functions. For example, with FDB isolation, it is
expected that drivers will need to be passed the bridge which requested
an FDB/MDB entry to be offloaded, and along with that bridge_dev, the
associated bridge_num should be passed too, in case the driver might
want to implement an isolation scheme based on that number.

We already pass the {bridge_dev, bridge_num} pair to the TX forwarding
offload switch API, however we'd like to remove that and squash it into
the basic bridge join/leave API. So that means we need to pass this
pair to the bridge join/leave API.

During dsa_port_bridge_leave, first we unset dp->bridge_dev, then we
call the driver's .port_bridge_leave with what used to be our
dp->bridge_dev, but provided as an argument.

When bridge_dev and bridge_num get folded into a single structure, we
need to preserve this behavior in dsa_port_bridge_leave: we need a copy
of what used to be in dp->bridge.

Switch drivers check bridge membership by comparing dp->bridge_dev with
the provided bridge_dev, but now, if we provide the struct dsa_bridge as
a pointer, they cannot keep comparing dp->bridge to the provided
pointer, since this only points to an on-stack copy. To make this
obvious and prevent driver writers from forgetting and doing stupid
things, in this new API, the struct dsa_bridge is provided as a full
structure (not very large, contains an int and a pointer) instead of a
pointer. An explicit comparison function needs to be used to determine
bridge membership: dsa_port_offloads_bridge().

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>

1 files changed, 6 insertions, 4 deletions

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index b4f9df4e38b2..da6ff99ba5ed 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -52,7 +52,7 @@ struct dsa_notifier_ageing_time_info {
 
 /* DSA_NOTIFIER_BRIDGE_* */
 struct dsa_notifier_bridge_info {
-	struct net_device *br;
+	struct dsa_bridge bridge;
 	int tree_index;
 	int sw_index;
 	int port;
@@ -374,7 +374,7 @@ dsa_find_designated_bridge_port_by_vid(struct net_device *master, u16 vid)
 		if (dp->type != DSA_PORT_TYPE_USER)
 			continue;
 
-		if (!dp->bridge_dev)
+		if (!dp->bridge)
 			continue;
 
 		if (dp->stp_state != BR_STATE_LEARNING &&
@@ -403,7 +403,7 @@ dsa_find_designated_bridge_port_by_vid(struct net_device *master, u16 vid)
 /* If the ingress port offloads the bridge, we mark the frame as autonomously
  * forwarded by hardware, so the software bridge doesn't forward in twice, back
  * to us, because we already did. However, if we're in fallback mode and we do
- * software bridging, we are not offloading it, therefore the dp->bridge_dev
+ * software bridging, we are not offloading it, therefore the dp->bridge
  * pointer is not populated, and flooding needs to be done by software (we are
  * effectively operating in standalone ports mode).
  */
@@ -411,7 +411,7 @@ static inline void dsa_default_offload_fwd_mark(struct sk_buff *skb)
 {
 	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
 
-	skb->offload_fwd_mark = !!(dp->bridge_dev);
+	skb->offload_fwd_mark = !!(dp->bridge);
 }
 
 /* Helper for removing DSA header tags from packets in the RX path.
@@ -508,6 +508,8 @@ int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
 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);
+struct dsa_bridge *dsa_tree_bridge_find(struct dsa_switch_tree *dst,
+					const struct net_device *br);
 
 /* tag_8021q.c */
 int dsa_tag_8021q_bridge_join(struct dsa_switch *ds,