openvswitch: Use exact lookup for flow_get and flow_del.

Due to the race condition in userspace, there is chance that two
overlapping megaflows could be installed in datapath.  And this
causes userspace unable to delete the less inclusive megaflow flow
even after it timeout, since the flow_del logic will stop at the
first match of masked flow.

This commit fixes the bug by making the kernel flow_del and flow_get
logic check all masks in that case.

Introduced by 03f0d916a (openvswitch: Mega flow implementation).

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 574c3abc9b30..cf2d853646f0 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -456,6 +456,22 @@ struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *tbl,
 	return ovs_flow_tbl_lookup_stats(tbl, key, &n_mask_hit);
 }
 
+struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl,
+					  struct sw_flow_match *match)
+{
+	struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
+	struct sw_flow_mask *mask;
+	struct sw_flow *flow;
+
+	/* Always called under ovs-mutex. */
+	list_for_each_entry(mask, &tbl->mask_list, list) {
+		flow = masked_flow_lookup(ti, match->key, mask);
+		if (flow && ovs_flow_cmp_unmasked_key(flow, match))  /* Found */
+			return flow;
+	}
+	return NULL;
+}
+
 int ovs_flow_tbl_num_masks(const struct flow_table *table)
 {
 	struct sw_flow_mask *mask;