[ovs-dev] [PATCH branch-2.3] dpif-netdev: Avoid divide by zero.

Ben Pfaff blp at nicira.com
Wed Aug 6 16:47:05 UTC 2014

Otherwise creating the first dpif-netdev bridge fails because there are
no handlers:

  Program terminated with signal 8, Arithmetic exception.
  #0  0x080971e9 in dp_execute_cb (aux_=aux_ at entry=0xffcfaa54,
      packet=packet at entry=0xffcfac54, md=md at entry=0xffcfac84,
      a=a at entry=0x8f58930, may_steal=false) at ../lib/dpif-netdev.c:2154
  #1  0x080b5adb in odp_execute_actions__ (dp=dp at entry=0xffcfaa54,
      packet=packet at entry=0xffcfac54, steal=steal at entry=false,
      md=md at entry=0xffcfac84, actions=actions at entry=0x8f58930,
      actions_len=actions_len at entry=20,
      dp_execute_action=dp_execute_action at entry=0x8097040 <dp_execute_cb>,
      more_actions=more_actions at entry=false) at ../lib/odp-execute.c:218
  #2  0x080b5def in odp_execute_actions (dp=dp at entry=0xffcfaa54,
      packet=packet at entry=0xffcfac54, steal=steal at entry=false,
      md=md at entry=0xffcfac84, actions=0x8f58930, actions_len=20,
      dp_execute_action=dp_execute_action at entry=0x8097040 <dp_execute_cb>)
      at ../lib/odp-execute.c:285
  #3  0x08095098 in dp_netdev_execute_actions (actions_len=<optimized out>,
      actions=<optimized out>, md=0xffcfac84, may_steal=false,
      packet=0xffcfac54, key=0xffcfaa5c, dp=<optimized out>)
      at ../lib/dpif-netdev.c:2227
  #4  dpif_netdev_execute (dpif=0x8f59598, execute=0xffcfac78)
      at ../lib/dpif-netdev.c:1551
  #5  0x0809a56c in dpif_execute (dpif=0x8f59598,
      execute=execute at entry=0xffcfac78) at ../lib/dpif.c:1227
  #6  0x08071071 in check_variable_length_userdata (backer=<optimized out>)
      at ../ofproto/ofproto-dpif.c:1040
  #7  open_dpif_backer (backerp=0x8f5834c, type=<optimized out>)
      at ../ofproto/ofproto-dpif.c:921
  #8  construct (ofproto_=0x8f581c0) at ../ofproto/ofproto-dpif.c:1120
  #9  0x080675e0 in ofproto_create (datapath_name=0x8f57310 "br0",
      datapath_type=<optimized out>, ofprotop=ofprotop at entry=0x8f576c8)
      at ../ofproto/ofproto.c:564
  #10 0x080529aa in bridge_reconfigure (ovs_cfg=ovs_cfg at entry=0x8f596d8)
      at ../vswitchd/bridge.c:572
  #11 0x08055e33 in bridge_run () at ../vswitchd/bridge.c:2339
  #12 0x0804cdbd in main (argc=9, argv=0xffcfb554)
      at ../vswitchd/ovs-vswitchd.c:116

This bug was introduced by commit 9bcefb956d8f (ofproto-dpif: fix an ovs
crash when dpif_recv_set returns error).

CC: Andy Zhou <azhou at nicira.com>
Signed-off-by: Ben Pfaff <blp at nicira.com>
This bug is only on branch-2.3.

 lib/dpif-netdev.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 69e15d7..78f8636 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -2150,11 +2150,13 @@ dp_execute_cb(void *aux_, struct ofpbuf *packet,
         userdata = nl_attr_find_nested(a, OVS_USERSPACE_ATTR_USERDATA);
-        dp_netdev_output_userspace(aux->dp, packet,
-                                   miniflow_hash_5tuple(aux->key, 0)
+        if (aux->dp->n_handlers > 0) {
+            dp_netdev_output_userspace(aux->dp, packet,
+                                       miniflow_hash_5tuple(aux->key, 0)
                                        % aux->dp->n_handlers,
-                                   DPIF_UC_ACTION, aux->key,
-                                   userdata);
+                                       DPIF_UC_ACTION, aux->key,
+                                       userdata);
+        }
         if (may_steal) {

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