ofproto: Use xlate map for uuid lookups.

The ofproto map 'all_ofproto_dpifs_by_uuid' does not support
concurrent accesses. It is however read by upcall handler threads
and written by the main thread at the same time.

Additionally, handler threads will change the ams_seq while
an ofproto is being destroyed, triggering crashes with the
following backtrace:

(gdb) bt
  hmap_next (hmap.h:398)
  seq_wake_waiters (seq.c:326)
  seq_change_protected (seq.c:134)
  seq_change (seq.c:144)
  ofproto_dpif_send_async_msg (ofproto_dpif.c:263)
  process_upcall (ofproto_dpif_upcall.c:1782)
  recv_upcalls (ofproto_dpif_upcall.c:1026)
  udpif_upcall_handler (ofproto/ofproto_dpif_upcall.c:945)
  ovsthread_wrapper (ovs_thread.c:734)

To solve both issues, remove the 'all_ofproto_dpifs_by_uuid'.
Instead, another map already storing ofprotos in xlate can be used.

During an ofproto destruction, its reference is removed from the current
xlate xcfg. Such change is committed only after all threads have quiesced
at least once during xlate_txn_commit(). This wait ensures that the
removal is seen by all threads, rendering impossible for a thread to
still hold a reference while the destruction proceeds.

Furthermore, the xlate maps are copied during updates instead of
being written in place. It is thus correct to read xcfg->xbridges while
inserting or removing from new_xcfg->xbridges.

Finally, now that ofproto_dpifs lookups are done through xcfg->xbridges,
it is important to use a high level of entropy. As it used the ofproto pointer
hashed, fewer bits were random compared to the uuid key used in
'all_ofproto_dpifs_by_uuid'. To solve this, use the ofproto uuid as the key
in xbridges as well, improving entropy.

Fixes: fcb9579be3c7 ("ofproto: Add 'ofproto_uuid' and 'ofp_in_port' to user action cookie.")
Suggested-by: Adrian Moreno <amorenoz@redhat.com>
Acked-by: Adrian Moreno <amorenoz@redhat.com>
Acked-by: Alin-Gabriel Serdean <aserdean@ovn.org>
Tested-by: Alin-Gabriel Serdean <aserdean@ovn.org>
Signed-off-by: Gaetan Rivet <grive@u256.net>
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Co-authored-by: Yunjian Wang <wangyunjian@huawei.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

1 files changed, 19 insertions, 2 deletions

diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 6ba25f642..cc9c1c628 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -865,7 +865,7 @@ xlate_xbridge_init(struct xlate_cfg *xcfg, struct xbridge *xbridge)
     ovs_list_init(&xbridge->xbundles);
     hmap_init(&xbridge->xports);
     hmap_insert(&xcfg->xbridges, &xbridge->hmap_node,
-                hash_pointer(xbridge->ofproto, 0));
+                uuid_hash(&xbridge->ofproto->uuid));
 }
 
 static void
@@ -1639,7 +1639,7 @@ xbridge_lookup(struct xlate_cfg *xcfg, const struct ofproto_dpif *ofproto)
 
     xbridges = &xcfg->xbridges;
 
-    HMAP_FOR_EACH_IN_BUCKET (xbridge, hmap_node, hash_pointer(ofproto, 0),
+    HMAP_FOR_EACH_IN_BUCKET (xbridge, hmap_node, uuid_hash(&ofproto->uuid),
                              xbridges) {
         if (xbridge->ofproto == ofproto) {
             return xbridge;
@@ -1661,6 +1661,23 @@ xbridge_lookup_by_uuid(struct xlate_cfg *xcfg, const struct uuid *uuid)
     return NULL;
 }
 
+struct ofproto_dpif *
+xlate_ofproto_lookup(const struct uuid *uuid)
+{
+    struct xlate_cfg *xcfg = ovsrcu_get(struct xlate_cfg *, &xcfgp);
+    struct xbridge *xbridge;
+
+    if (!xcfg) {
+        return NULL;
+    }
+
+    xbridge = xbridge_lookup_by_uuid(xcfg, uuid);
+    if (xbridge != NULL) {
+        return xbridge->ofproto;
+    }
+    return NULL;
+}
+
 static struct xbundle *
 xbundle_lookup(struct xlate_cfg *xcfg, const struct ofbundle *ofbundle)
 {