Because trace packet use the ofproto, so you need to use the ofproto used port number

Use below command to find out ofproto port and vswitch port mapping:

# ovs-ofctl dump-ports-desc br-int
OFPST_PORT_DESC reply (xid=0x2):
 3(ovn-b250f7-0): addr:82:d1:09:0a:7f:9a
    config:     0
    state:      0
    speed: 0 Mbps now, 0 Mbps max

 4(ovn-f4001b-0): addr:0a:94:ed:2a:bc:9f
    config:     0
    state:      0
    speed: 0 Mbps now, 0 Mbps max

 7(tap88eb131b-2b): addr:fe:16:3e:90:3a:24
    config:     0
    state:      0
    current:    10MB-FD COPPER
    speed: 10 Mbps now, 0 Mbps max

 8(tape61d293f-8d): addr:fe:16:3e:ff:fe:0c
   config:     0
   state:      0
   current:    10MB-FD COPPER
   speed: 10 Mbps now, 0 Mbps max
   LOCAL(br-int): addr:de:63:13:48:99:45
   config:     PORT_DOWN
   state:      LINK_DOWN
   speed: 0 Mbps now, 0 Mbps max

Then use below command to input packet to trace the matched flows:

The field name can be find in http://openvswitch.org/support/dist-docs/ovs-fields.7.pdf

# ovs-appctl ofproto/trace br-int in_port=8,tcp,nw_src=1.1.1.12
Flow: tcp,in_port=8,vlan_tci=0x0000,dl_src=00:00:00:00:00:00,dl_dst=00:00:00:00:00:00,nw_src=1.1.1.12,nw_dst=0.0.0.0,nw_tos=0,nw_ecn=0,nw_ttl=0,tp_src=0,tp_dst=0,tcp_flags=0

Bridge("br-int")
----------------
 0. in_port=8, priority 100
    set_field:0x4->reg13
    set_field:0x5->reg11
    set_field:0x6->reg12
    set_field:0x3->metadata
    set_field:0x3->reg14
    resubmit(,16)
16. No match.
    drop