Problem:

I create two tap interfaces in different network namespaces and L2 cross-connect inside a vpp instance. Set up addresses - ping works.
But, if i delete the target namespace from the host - ping continues to work.
I've tested it with l2xc/l3xc + tap/tun - the result is the same.
Moreover, I see the same behavior with af-packet if I configure it via vpp api. But unfortunately I can't reproduce it using vppctl...
Does anyone have any idea?

Steps to reproduce:

l2xc + tap
1. Create two netns vpp1 and vpp2 on host:

# ip netns add vpp1
# ip netns add vpp2

2. Create two tap interfaces on vpp:

DBGvpp# create tap host-ns vpp1
DBGvpp# set int state tap0 up 
DBGvpp# create tap host-ns vpp2 
DBGvpp# set int state tap1 up

3.  Let's create l2xc:

DBGvpp# set interface l2 xconnect tap0 tap1
DBGvpp# set interface l2 xconnect tap1 tap0

4. Finish setting up interfaces in target network namespaces:

# ip netns exec vpp1 ip link set tap0 up
# ip netns exec vpp2 ip link set tap0 up
# ip netns exec vpp1 ip address add 10.10.1.1/24 dev tap0
# ip netns exec vpp2 ip address add 10.10.1.2/24 dev tap0

5. Ping:

# ip netns exec vpp1 ping 10.10.1.2

It works fine.
6. Let's delete vpp2 netns:

# ip netns delete vpp2

7. Ping continues to work!

Additional information

DBGvpp# show version
vpp v22.02-rc0~492-gf715b33f1 built by art on art-c at 2022-01-13T07:06:48