netfilter: flowtable: Add API for registering to flow table events

Let drivers to add their cb allowing them to receive flow offload events
of type TC_SETUP_CLSFLOWER (REPLACE/DEL/STATS) for flows managed by the
flow table.
Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netfilter/nf_flow_table.h

@@ -44,6 +44,7 @@ struct nf_flowtable {
 	struct delayed_work		gc_work;
 	unsigned int			flags;
 	struct flow_block		flow_block;
+	struct mutex			flow_block_lock; /* Guards flow_block */
 	possible_net_t			net;
 };
 
@@ -129,6 +130,11 @@ struct nf_flow_route {
 struct flow_offload *flow_offload_alloc(struct nf_conn *ct);
 void flow_offload_free(struct flow_offload *flow);
 
+int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
+				 flow_setup_cb_t *cb, void *cb_priv);
+void nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
+				  flow_setup_cb_t *cb, void *cb_priv);
+
 int flow_offload_route_init(struct flow_offload *flow,
 			    const struct nf_flow_route *route);
 

net/netfilter/nf_flow_table_core.c

@@ -372,6 +372,50 @@ static void nf_flow_offload_work_gc(struct work_struct *work)
 	queue_delayed_work(system_power_efficient_wq, &flow_table->gc_work, HZ);
 }
 
+int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
+				 flow_setup_cb_t *cb, void *cb_priv)
+{
+	struct flow_block *block = &flow_table->flow_block;
+	struct flow_block_cb *block_cb;
+	int err = 0;
+
+	mutex_lock(&flow_table->flow_block_lock);
+	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
+	if (block_cb) {
+		err = -EEXIST;
+		goto unlock;
+	}
+
+	block_cb = flow_block_cb_alloc(cb, cb_priv, cb_priv, NULL);
+	if (IS_ERR(block_cb)) {
+		err = PTR_ERR(block_cb);
+		goto unlock;
+	}
+
+	list_add_tail(&block_cb->list, &block->cb_list);
+
+unlock:
+	mutex_unlock(&flow_table->flow_block_lock);
+	return err;
+}
+EXPORT_SYMBOL_GPL(nf_flow_table_offload_add_cb);
+
+void nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
+				  flow_setup_cb_t *cb, void *cb_priv)
+{
+	struct flow_block *block = &flow_table->flow_block;
+	struct flow_block_cb *block_cb;
+
+	mutex_lock(&flow_table->flow_block_lock);
+	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
+	if (block_cb)
+		list_del(&block_cb->list);
+	else
+		WARN_ON(true);
+	mutex_unlock(&flow_table->flow_block_lock);
+}
+EXPORT_SYMBOL_GPL(nf_flow_table_offload_del_cb);
+
 static int nf_flow_nat_port_tcp(struct sk_buff *skb, unsigned int thoff,
 				__be16 port, __be16 new_port)
 {
@@ -494,6 +538,7 @@ int nf_flow_table_init(struct nf_flowtable *flowtable)
 
 	INIT_DEFERRABLE_WORK(&flowtable->gc_work, nf_flow_offload_work_gc);
 	flow_block_init(&flowtable->flow_block);
+	mutex_init(&flowtable->flow_block_lock);
 
 	err = rhashtable_init(&flowtable->rhashtable,
 			      &nf_flow_offload_rhash_params);
@@ -550,11 +595,13 @@ void nf_flow_table_free(struct nf_flowtable *flow_table)
 	mutex_lock(&flowtable_lock);
 	list_del(&flow_table->list);
 	mutex_unlock(&flowtable_lock);
+
 	cancel_delayed_work_sync(&flow_table->gc_work);
 	nf_flow_table_iterate(flow_table, nf_flow_table_do_cleanup, NULL);
 	nf_flow_table_iterate(flow_table, nf_flow_offload_gc_step, flow_table);
 	nf_flow_table_offload_flush(flow_table);
 	rhashtable_destroy(&flow_table->rhashtable);
+	mutex_destroy(&flow_table->flow_block_lock);
 }
 EXPORT_SYMBOL_GPL(nf_flow_table_free);
 

net/netfilter/nf_flow_table_offload.c

@@ -610,6 +610,7 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
 	if (cmd == FLOW_CLS_REPLACE)
 		cls_flow.rule = flow_rule->rule;
 
+	mutex_lock(&flowtable->flow_block_lock);
 	list_for_each_entry(block_cb, block_cb_list, list) {
 		err = block_cb->cb(TC_SETUP_CLSFLOWER, &cls_flow,
 				   block_cb->cb_priv);
@@ -618,6 +619,7 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
 
 		i++;
 	}
+	mutex_unlock(&flowtable->flow_block_lock);
 
 	return i;
 }
@@ -692,8 +694,10 @@ static void flow_offload_tuple_stats(struct flow_offload_work *offload,
 			     FLOW_CLS_STATS,
 			     &offload->flow->tuplehash[dir].tuple, &extack);
 
+	mutex_lock(&flowtable->flow_block_lock);
 	list_for_each_entry(block_cb, &flowtable->flow_block.cb_list, list)
 		block_cb->cb(TC_SETUP_CLSFLOWER, &cls_flow, block_cb->cb_priv);
+	mutex_unlock(&flowtable->flow_block_lock);
 	memcpy(stats, &cls_flow.stats, sizeof(*stats));
 }