Comment 55 for bug 1953165

without the transparent binding option it looks like follows:

docker exec -ti neutron_dhcp_agent ls /var/lib/neutron/ns-metadata-proxy/ | sort
0614c965-c47d-47b4-bae2-acf24b191605.conf
0b62624a-4be2-479a-9fe6-40d7fc5c9b83.conf
0fb9e437-9d62-4144-9d5d-b2b062680b89.conf
211261df-4c82-4d30-b460-7296e555758f.conf
25aadba7-44bf-41bf-aaff-015a581e2d21.conf
6810dff4-b8c0-40c3-a755-62b5ebaf8369.conf
6bd9cbec-4b84-4adc-ac9c-901cb90a8eec.conf
79c41e38-5a10-4de3-83e9-bd69c8f97092.conf
8c15292e-9335-438b-b166-0a3cffd5f233.conf
a88e1f6d-df26-49c7-b562-52354decb3d2.conf
c32bbe2e-bbdf-4ad7-87ff-1ab05881a3e5.conf
cd696a35-adc7-4a8e-aa81-fdabd0ceafde.conf
e346b34b-2e47-4221-888a-4d1880cb34d8.conf
e81fa39a-79af-4028-a5dd-df7cbc6ad762.conf

for i in $(ip netns ls | awk '/qdhcp-/ { print $1 }'); do if [ $(ip netns pids $i | wc -l | grep 2) ]; then echo $i; fi ; done | sort
qdhcp-25aadba7-44bf-41bf-aaff-015a581e2d21
qdhcp-6810dff4-b8c0-40c3-a755-62b5ebaf8369
qdhcp-6bd9cbec-4b84-4adc-ac9c-901cb90a8eec
qdhcp-8c15292e-9335-438b-b166-0a3cffd5f233
qdhcp-cd696a35-adc7-4a8e-aa81-fdabd0ceafde
qdhcp-e346b34b-2e47-4221-888a-4d1880cb34d8

So haproxy fails to start/bind in some of the netns:

2023-05-17 18:11:41.378 7 ERROR neutron.agent.linux.utils [-] Exit code: 1; Cmd: ['ip', 'netns', 'exec', 'qdhcp-e81fa39a-79af-4028-a5dd-df7cbc6ad762', 'haproxy', '-f', '/var/lib/neutron/ns-metadata-proxy/e81fa39a-79af-4028-a5dd-df7cbc6ad762.conf']; Stdin: ; Stdout: ; Stderr: [NOTICE] (708) : haproxy version is 2.4.22-0ubuntu0.22.04.1
[NOTICE] (708) : path to executable is /usr/sbin/haproxy
[ALERT] (708) : Starting proxy listener: cannot bind socket (Cannot assign requested address) [fe80::a9fe:a9fe:80]
[ALERT] (708) : [haproxy.main()] Some protocols failed to start their listeners! Exiting.