[ovs-dev] dpif-netdev bug regarding packet matches or ufids?

Ben Pfaff blp at ovn.org
Mon Oct 8 17:44:27 UTC 2018


Hi Ian (or others), do you have any thoughts about this?

On Fri, Sep 28, 2018 at 04:24:33PM -0700, Ben Pfaff wrote:
> I have been playing with the OFTest framework off and on over the last
> few months and I believe it's caught an actual bug with its
> DirectVlanPackets test.  I'm appending a script that demonstrates it.
> To see it, run "make sandbox" then execute the script inside it.
> 
> At some level at least, the problem is in dpif-netdev, which during the
> test logs messages like this indicating that a datapath flow can't be
> found and therefore can't be modified:
> 
>     WARN|dummy at ovs-dummy: failed to put[modify] (No such file or
>     directory) ufid:b2fe59af-26bd-4aa0-960e-fd559dc10c54
>     skb_priority(0/0),skb_mark(0/0),ct_state(0/0),ct_zone(0/0),ct_mark(0/0),ct_label(0/0),recirc_id(0),dp_hash(0/0),in_port(1),packet_type(ns=0,id=0),eth(src=00:06:07:08:09:0a,dst=00:01:02:03:04:05),eth_type(0x8100),vlan(vid=1000/0x0,pcp=5/0x0),encap(eth_type(0x0800),ipv4(src=127.0.0.1/0.0.0.0,dst=127.0.0.1/0.0.0.0,proto=0/0,tos=0/0,ttl=64/0,frag=no)),
>     actions:userspace(pid=0,controller(reason=7,dont_send=0,continuation=0,recirc_id=1,rule_cookie=0,controller_id=0,max_len=65535))
> 
> It's possible that the caller is screwing up by providing a flow match
> different from one in the datapath flow table.  I have not looked at
> that question.  But the really strange thing here is that the caller is
> providing a ufid and dpif-netdev is ignoring it.  When I make it honor
> the ufid, like the following, then the test suddenly starts working.
> This seems like a bug to me.
> 
> (The following patch is not actually the real fix because the code
> should still look at the key if no ufid was provided.)
> 
> Any thoughts?
> 
> Thanks,
> 
> Ben.
> 
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index e322f5553fa8..4855cc08f7b7 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -3273,7 +3273,7 @@ dp_netdev_flow_add(struct dp_netdev_pmd_thread *pmd,
>  
>  static int
>  flow_put_on_pmd(struct dp_netdev_pmd_thread *pmd,
> -                struct netdev_flow_key *key,
> +                struct netdev_flow_key *key OVS_UNUSED,
>                  struct match *match,
>                  ovs_u128 *ufid,
>                  const struct dpif_flow_put *put,
> @@ -3287,7 +3287,7 @@ flow_put_on_pmd(struct dp_netdev_pmd_thread *pmd,
>      }
>  
>      ovs_mutex_lock(&pmd->flow_mutex);
> -    netdev_flow = dp_netdev_pmd_lookup_flow(pmd, key, NULL);
> +    netdev_flow = dp_netdev_pmd_find_flow(pmd, ufid, NULL, 0);
>      if (!netdev_flow) {
>          if (put->flags & DPIF_FP_CREATE) {
>              if (cmap_count(&pmd->flow_table) < MAX_FLOWS) {
> 
> 
> 
> --8<--------------------------cut here-------------------------->8--
> 
> #! /bin/sh -ex
> 
> # Create a bridge and add port p1 on port 1, p2 on port 2
> ovs-appctl vlog/set netdev_dummy dpif
> ovs-vsctl --if-exists del-br br0 \
>        -- add-br br0 \
>        -- add-port br0 p1 -- set interface p1 ofport_request=1 options:tx_pcap=p1-tx.pcap options:rxq_pcap=p1-rx.pcap \
>        -- add-port br0 p2 -- set interface p2 ofport_request=2 options:tx_pcap=p2-tx.pcap options:rxq_pcap=p2-rx.pcap
> 
> # Add a flow that directs some packets received on p1 to p2 and the
> # rest back out p1.
> #
> # Then inject a packet of the form that should go to p2.  Dump the
> # datapath flow to see that it goes to p2 ("actions:2").  Trace the
> # same packet for good measure, to also see that it should go to p2.
> packet=00010203040500060708090a8100a3e80800450000140001000040007ce77f0000017f000001
> ovs-ofctl add-flow br0 priority=1,ip,in_port=1,dl_src=00:06:07:08:09:0a,dl_dst=00:01:02:03:04:05,actions=output:2
> ovs-ofctl add-flow br0 priority=0,in_port=1,actions=IN_PORT
> ovs-appctl netdev-dummy/receive p1 $packet
> ovs-appctl ofproto/trace br0 in_port=p1 $packet
> ovs-appctl dpif/dump-flows br0
> 
> # Delete the flows, then add new flows that would not match the same
> # packet as before.
> ovs-ofctl del-flows br0
> ovs-ofctl add-flow br0 priority=1,in_port=1,dl_src=00:06:07:08:09:0a,dl_dst=00:01:02:03:04:05,dl_type=0x0801,actions=output:2
> ovs-ofctl add-flow br0 priority=0,in_port=1,actions=IN_PORT
> 
> # Give the datapath a few seconds to revalidate.
> sleep 2
> 
> # Now inject the same packet again.  It should go to p1 because it
> # only matches the priority-0 flow, as shown by the trace.  However, instead,
> # the original datapath flow is still there and its counters get incremented.
> ovs-appctl netdev-dummy/receive p1 $packet
> ovs-appctl ofproto/trace br0 in_port=p1 $packet
> ovs-appctl dpif/dump-flows br0
> 
> # Give the datapath some time to expire the flow.
> sleep 12
> 
> # Try again.
> ovs-appctl netdev-dummy/receive p1 $packet
> ovs-appctl ofproto/trace br0 in_port=p1 $packet
> ovs-appctl dpif/dump-flows br0


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