[ovs-dev] [PATCH 1/4] ofproto: Update access rules for 'flow_cookie'.

Ben Pfaff blp at ovn.org
Wed Dec 7 07:28:40 UTC 2016


The 'flow_cookie' member of struct rule is read during flow translation
without holding a mutex, breaking the documented OVS_GUARDED access rule.
However, the flow_cookie member is actually never modified after a rule is
initialized, so this commit changes the access rules to reflect that.

Signed-off-by: Ben Pfaff <blp at ovn.org>
---
 ofproto/ofproto-provider.h | 4 ++--
 ofproto/ofproto.c          | 5 +++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/ofproto/ofproto-provider.h b/ofproto/ofproto-provider.h
index c515779..3739ebc 100644
--- a/ofproto/ofproto-provider.h
+++ b/ofproto/ofproto-provider.h
@@ -365,8 +365,8 @@ struct rule {
     struct ovs_refcount ref_count;
 
     /* A "flow cookie" is the OpenFlow name for a 64-bit value associated with
-     * a flow.. */
-    ovs_be64 flow_cookie OVS_GUARDED;
+     * a flow. */
+    const ovs_be64 flow_cookie; /* Immutable once rule is constructed. */
     struct hindex_node cookie_node OVS_GUARDED_BY(ofproto_mutex);
 
     enum ofputil_flow_mod_flags flags OVS_GUARDED;
diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 4f43c45..58295a1 100644
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -4859,7 +4859,7 @@ ofproto_rule_create(struct ofproto *ofproto, struct cls_rule *cr,
 
     ovs_mutex_init(&rule->mutex);
     ovs_mutex_lock(&rule->mutex);
-    rule->flow_cookie = new_cookie;
+    *CONST_CAST(ovs_be64 *, &rule->flow_cookie) = new_cookie;
     rule->created = rule->modified = time_msec();
     rule->idle_timeout = idle_timeout;
     rule->hard_timeout = hard_timeout;
@@ -5098,7 +5098,8 @@ replace_rule_start(struct ofproto *ofproto, struct ofproto_flow_mod *ofm,
                 new_rule->created = old_rule->created;
             }
             if (!change_cookie) {
-                new_rule->flow_cookie = old_rule->flow_cookie;
+                *CONST_CAST(ovs_be64 *, &new_rule->flow_cookie)
+                    = old_rule->flow_cookie;
             }
             ovs_mutex_unlock(&old_rule->mutex);
             ovs_mutex_unlock(&new_rule->mutex);
-- 
2.10.2



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