[ovs-dev] [PATCH 2/2] dpif-netdev: Get rid of broken dpif pointer in dp_netdev structure.

[Ilya Maximets]

This pointer was introduced in July 2014 by commit
6b31e07347ad ("dpif-netdev: Polling threads directly call ofproto upcall functions.")
and it was broken right from this point because dpif_netdev_open()
updates it on each call with the pointer to a newly allocated
'dpif' structure that becomes invalid on the next dpif_netdev_close().
Since dpif_open/close() always happens asynchronously from different
threads and pointer is not protected by rcu or mutex (it's not even
atomic) it's not possible to safely use it.  Thankfully the actual
usage was in repository for less than 3 weeks and was removed by
commit 623540e4617e ("dpif-netdev: Streamline miss handling.").  Until
recently this pointer was used in order to pass it to dpif_flow_hash().
Another luck is that dpif_flow_hash() didn't use the 'dpif' argument.

However, we tried to use it while netdev offloading by commit
30115809da2e ("dpif-netdev: Use netdev-offload API for port lookup while offloading.")
and that unveiled the issue.

Now that all the code that used this pointer was cleaned up we can
just remove it from the structure to avoid possible misuse in the
future.

Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
---
 lib/dpif-netdev.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index ffb3cd420..38d1f12ef 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -303,7 +303,6 @@ struct pmd_auto_lb {
 struct dp_netdev {
     const struct dpif_class *const class;
     const char *const name;
-    struct dpif *dpif;
     struct ovs_refcount ref_cnt;
     atomic_flag destroyed;
 
@@ -1618,7 +1617,6 @@ dpif_netdev_open(const struct dpif_class *class, const char *name,
     }
     if (!error) {
         *dpifp = create_dpif_netdev(dp);
-        dp->dpif = *dpifp;
     }
     ovs_mutex_unlock(&dp_netdev_mutex);
 
-- 
2.17.1