Comment 0 for bug 1808541

I am using Queens release and VM's tap interfaces are plugged into ovs br-int.
I'm watching a case when openflow entries are not totally removed when I stop my VM (name='my-vm').
It is only reproducable when there is some another activity on a node for different VMs: in my case I attach new network to another VM (name='vm-other')

ovs-agent logs in attach.

I managed to simulate the issue using next steps:

1) grep by mac current openflow entries for my-vm:

# ovs-ofctl dump-flows br-int | grep fa:16:3e:ec:d3:45
 cookie=0xf4d7d970f5382f3d, duration=93.162s, table=60, n_packets=146, n_bytes=21001, idle_age=4, priority=90,dl_vlan=9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],load:0x9->NXM_NX_REG6[],strip_vlan,resubmit(,81)
 cookie=0xf4d7d970f5382f3d, duration=93.162s, table=71, n_packets=2, n_bytes=84, idle_age=4, priority=95,arp,reg5=0xa3,in_port=163,dl_src=fa:16:3e:ec:d3:45,arp_spa=10.94.152.212 actions=NORMAL
 cookie=0xf4d7d970f5382f3d, duration=93.162s, table=71, n_packets=28, n_bytes=2448, idle_age=9, priority=65,ip,reg5=0xa3,in_port=163,dl_src=fa:16:3e:ec:d3:45,nw_src=10.94.152.212 actions=ct(table=72,zone=NXM_NX_REG6[0..15])
 cookie=0xf4d7d970f5382f3d, duration=93.162s, table=71, n_packets=0, n_bytes=0, idle_age=93, priority=65,ipv6,reg5=0xa3,in_port=163,dl_src=fa:16:3e:ec:d3:45,ipv6_src=fe80::f816:3eff:feec:d345 actions=ct(table=72,zone=NXM_NX_REG6[0..15])
 cookie=0xf4d7d970f5382f3d, duration=93.162s, table=73, n_packets=0, n_bytes=0, idle_age=3401, priority=100,reg6=0x9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],resubmit(,81)
#

2) # ps ax | grep libvirt
 4887 pts/6 S+ 0:00 grep --color=auto libvirt
 3934 ? Sl 0:18 /usr/libexec/qemu-kvm -name guest=instance-00000012,debug-threads=on -S -object secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-131-instance-00000012/master-key.aes -machine pc-i440fx-vz7.8.0,accel=kvm,usb=off,dump-guest-core=off -cpu Westmere-IBRS,vme=on,ss=on,pcid=on,x2apic=on,tsc-deadline=on,hypervisor=on,arat=on,tsc_adjust=on,ssbd=on,stibp=on,pdpe1gb=on,rdtscp=on,aes=off,+kvmclock -m 512 -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -numa node,nodeid=0,cpus=0,mem=512 -uuid 89fccc31-96a6-47ce-abd1-e40fba7274e6 -smbios type=1,manufacturer=Virtuozzo Infrastructure Platform,product=OpenStack Compute,version=17.0.6-1.vl7,serial=71f55add-ef93-4ec2-a4dd-ab8098b6312d,uuid=89fccc31-96a6-47ce-abd1-e40fba7274e6,family=Virtual Machine -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-131-instance-00000012/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -global kvm-pit.lost_tick_policy=discard -no-shutdown -boot strict=on -device nec-usb-x,id=usb,bus=pci.0,addr=0x4 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x5 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x6 -drive file=/mnt/vstorage/vols/datastores/cinder/volume-e30d1874-d68e-4578-bf89-aa599e8383c7/volume-e30d1874-d68e-4578-bf89-aa599e8383c7,format=qcow2,if=none,id=drive-scsi0-0-0-0,cache=none,l2-cache-size=128M,discard=unmap,aio=native -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1,logical_block_size=512,physical_block_size=4096,serial=e30d1874-d68e-4578-bf89-aa599e8383c7 -netdev tap,fd=28,id=hostnet0,vhost=on,vhostfd=30 -device virtio-net-pci,host_mtu=1500,netdev=hostnet0,id=net0,mac=fa:16:3e:ec:d3:45,bus=pci.0,addr=0x3 -chardev pty,id=charserial0,logfile=/mnt/vstorage/vols/datastores/nova/instances/89fccc31-96a6-47ce-abd1-e40fba7274e6/console.log,logappend=on -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/org.qemu.guest_agent.0.instance-00000012.sock,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -chardev socket,id=charchannel1,path=/var/lib/libvirt/qemu/org.qemu.guest_agent.1.instance-00000012.sock,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=org.qemu.guest_agent.1 -device usb-tablet,id=input0,bus=usb.0,port=1 -vnc 10.10.1.237:0 -device VGA,id=video0,vgamem_mb=16,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -device vmcoreinfo -device pvpanic,ioport=1285 -msg timestamp=on
24553 ? Ssl 11:44 /usr/sbin/libvirtd --listen

Note: "-netdev tap,fd=28", so, net device is passed to qemu as handle and AFAIU tap interface is auto removed (by kernel) when qemu process exits.

3) SIGSTOP libvirtd to emulate port deletion delay that is performed by libvirtd when guest is stopped
(I believe libvirtd removes port when quest is stopped in the way like 'ovs-vsctl --timeout=5 -- --if-exists del-port taped0487c9-23')

# kill -SIGSTOP 24553
#

4) Kill the quest:
# kill -9 3934
#

Ovs agent logs right after killing:

2018-12-14 17:18:26.600 7 DEBUG neutron.agent.linux.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["568b058e-382a-4c50-a185-45807107190b","old",null,163,null],["","new","taped0487c9-23",-1,["map",[["attached-mac","fa:16:3e:ec:d3:45"],["iface-id","ed0487c9-23b2-4bea-9a17-567b7f52d7fc"],["iface-status","active"],["vm-id","89fccc31-96a6-47ce-abd1-e40fba7274e6"]]]]],"headings":["row","action","name","ofport","external_ids"]} _read_stdout /usr/lib/python2.7/site-packages/neutron/agent/linux/async_process.py:239

Really:
# ovs-vsctl --columns name,ofport,error find Interface name='taped0487c9-23'
name : "taped0487c9-23"
ofport : -1
error : "could not open network device taped0487c9-23 (No such device)"
# ip a s taped0487c9-23
Device "taped0487c9-23" does not exist.
#

5) emulate parallel guest device adding (i.e. inforce rpc_loop to process ports):
# ip tuntap add dev my-tap mode tap
# ovs-vsctl add-port br-int my-tap
#

Right after adding rpc_loop starts to process ports and there is warning in logs:
2018-12-14 17:21:12.520 7 WARNING neutron.agent.common.ovs_lib [req-338406ef-81c5-4268-9463-f2e9435892ee - - - - -] ofport: -1 for VIF: ed0487c9-23b2-4bea-9a17-567b7f52d7fc is not a positive integer

Part of openflow entries are deleted but not all:

# ovs-ofctl dump-flows br-int | grep fa:16:3e:ec:d3:45
 cookie=0xf4d7d970f5382f3d, duration=905.467s, table=60, n_packets=176, n_bytes=23641, idle_age=367, priority=90,dl_vlan=9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],load:0x9->NXM_NX_REG6[],strip_vlan,resubmit(,81)
 cookie=0xf4d7d970f5382f3d, duration=905.467s, table=73, n_packets=0, n_bytes=0, idle_age=4213, priority=100,reg6=0x9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],resubmit(,81)
#

Continue libvirtd:

# kill -SIGCONT 24553
#

2018-12-14 17:24:58.557 7 DEBUG neutron.agent.linux.async_process [-] Output received from [ovsdb-client monitor tcp:127.0.0.1:6640 Interface name,ofport,external_ids --format=json]: {"data":[["568b058e-382a
-4c50-a185-45807107190b","delete","taped0487c9-23",-1,["map",[["attached-mac","fa:16:3e:ec:d3:45"],["iface-id","ed0487c9-23b2-4bea-9a17-567b7f52d7fc"],["iface-status","active"],["vm-id","89fccc31-96a6-47ce-a
bd1-e40fba7274e6"]]]]],"headings":["row","action","name","ofport","external_ids"]} _read_stdout /usr/lib/python2.7/site-packages/neutron/agent/linux/async_process.py:239

But flows are still here:
# ovs-ofctl dump-flows br-int | grep fa:16:3e:ec:d3:45
 cookie=0xf4d7d970f5382f3d, duration=1030.412s, table=60, n_packets=176, n_bytes=23641, idle_age=492, priority=90,dl_vlan=9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],load:0x9->NXM_NX_REG6[],strip_vlan,resubmit(,81)
 cookie=0xf4d7d970f5382f3d, duration=1030.412s, table=73, n_packets=0, n_bytes=0, idle_age=4338, priority=100,reg6=0x9,dl_dst=fa:16:3e:ec:d3:45 actions=load:0xa3->NXM_NX_REG5[],resubmit(,81)
#

Trace result for stopped VM:

# ovs-appctl ofproto/trace br-int in_port=12,tcp,dl_src=fa:16:3e:05:95:a1,dl_dst=fa:16:3e:ec:d3:45,nw_src=10.94.152.196,nw_dst=10.94.152.212
<cut>
bridge("br-int")
----------------
    thaw
        Resuming from table 72
72. ct_state=+new-est,ip,reg5=0xc, priority 74, cookie 0xf4d7d970f5382f3d
    resubmit(,73)
73. reg6=0x9,dl_dst=fa:16:3e:ec:d3:45, priority 100, cookie 0xf4d7d970f5382f3d
    set_field:0xa3->reg5
    resubmit(,81)
81. ct_state=+trk,reg5=0xa3, priority 80, cookie 0xf4d7d970f5382f3d
    resubmit(,82)
82. ct_state=+new-est,ip,reg5=0xa3, priority 74, cookie 0xf4d7d970f5382f3d
    ct(commit,zone=NXM_NX_REG6[0..15])
    drop
    output:163
     >> Nonexistent output port
    resubmit(,92)
92. priority 0, cookie 0xf4d7d970f5382f3d
    drop

Final flow: recirc_id=0x9b0,eth,tcp,reg5=0xa3,reg6=0x9,in_port=12,vlan_tci=0x0000,dl_src=fa:16:3e:05:95:a1,dl_dst=fa:16:3e:ec:d3:45,nw_src=10.94.152.196,nw_dst=10.94.152.212,nw_tos=0,nw_ecn=0,nw_ttl=0,tp_src=0,tp_dst=0,tcp_flags=0
Megaflow: recirc_id=0x9b0,ct_state=+new-est-rel-rpl+trk,eth,tcp,in_port=12,dl_dst=fa:16:3e:ec:d3:45,nw_frag=no
Datapath actions: ct(commit,zone=9)
#

If then migrate my-vm (in stopped state) to another node, then other-vm from current node lost connectivity to my-vm due to egress traffic from vm-other is going to 'Nonexistent output port'.

The issue looks like also actual for master.