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How does Docker Embedded DNS resolver work?

I know Docker has a embedded Dns resolver.
when I run a container in myself bridge:

$ docker run -it --rm --privileged --network=mybridge xxx bash

root@18243bfe6b50:/# cat /etc/resolv.conf
nameserver 127.0.0.11
options ndots:0

root@18243bfe6b50:/# netstat -anop
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Timer
tcp 0 0 127.0.0.11:45997 0.0.0.0:* LISTEN - off (0.00/0/0)
udp 0 0 127.0.0.11:49614 0.0.0.0:*

it shows there is a dns resolver, and iptables help do a port transfer.

root@18243bfe6b50:/# iptables -nvL -t nat

Chain DOCKER_OUTPUT (1 references)
pkts bytes target prot opt in out source destination
0 0 DNAT tcp – * * 0.0.0.0/0 127.0.0.11 tcp dpt:53 to:127.0.0.11:45997
0 0 DNAT udp – * * 0.0.0.0/0 127.0.0.11 udp dpt:53 to:127.0.0.11:49614

Chain DOCKER_POSTROUTING (1 references)
pkts bytes target prot opt in out source destination
0 0 SNAT tcp – * * 127.0.0.11 0.0.0.0/0 tcp spt:45997 to::53
0 0 SNAT udp – * * 127.0.0.11 0.0.0.0/0 udp spt:49614 to::53

but, which process is the dns resolver? I guess it is dockerd? but dockerd is running in host network namespace, obviously it is different with the container network namespace, also, I can not find dockerd has dns port listening in host:

root@test:~# netstat -tnop |grep dockerd
tcp 0 0 10.5.79.50:59540 10.5.79.50:2377 ESTABLISHED 3332/dockerd off (0.00/0/0)
tcp 0 0 127.0.0.1:35792 127.0.0.1:2377 ESTABLISHED 3332/dockerd off (0.00/0/0)
tcp6 0 0 10.5.79.50:2377 10.5.79.70:45934 ESTABLISHED 3332/dockerd off (0.00/0/0)
tcp6 0 0 127.0.0.1:2377 127.0.0.1:35792 ESTABLISHED 3332/dockerd off (0.00/0/0)
tcp6 0 0 10.5.79.50:2377 10.5.79.50:59540 ESTABLISHED 3332/dockerd off (0.00/0/0)

how does one process(dockerd) expose some ports in host namespace and some ports in other namespace(container)? I read some code, but still can not figure out, could anyone help answer?

thanks.

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