buildctl build RUN curl step failed, Could not resolve host

[alazalazalaz]

I did the following step to recurrent the error:

step1、vi docker-compose.yaml

version: '2.1'
services:
    buildkitd:
      image: moby/buildkit:v0.16.0
      container_name: buildkitd
      privileged: true
      restart: always
      command: ["--addr", "tcp://0.0.0.0:1234"]

step2、run the container
docker-compose -f docker-compose.yaml up -d buildkitd
step3、entry the container
docker exec -it 3a76a7e82807 /bin/sh
step4、test the container network

/ # nslookup www.google.com
Server:		127.0.0.11
Address:	127.0.0.11:53

Non-authoritative answer:
Name:	www.google.com
Address: 172.217.163.36

Non-authoritative answer:
Name:	www.google.com
Address: 2404:6800:4012:4::2004

the network is OK.

step5、create a Dockerfile, vi Dockerfile (still in the container)

FROM alpine/curl

RUN nslookup www.google.com

step6、build the Dockerfile (still in the container)
/ # buildctl --addr=tcp://0.0.0.0:1234 build --frontend=dockerfile.v0 --local context=. --local dockerfile=. --progress=plain
step7、 encounter the ERROR!

#4 [1/2] FROM docker.io/alpine/curl:latest@sha256:a9599b0ecdab1fb3c798985836248c51ba27577218e93c99bcc1ec61969acaf8
#4 extracting sha256:1010f67b3369ce6414bb7f1ebaea67db6912f2d4045960ee5f5386e56196de8a 0.0s done
#4 DONE 7.6s

#5 [2/2] RUN nslookup www.google.com
#5 10.31 nslookup: can't connect to remote host: Address not available
#5 ERROR: process "/bin/sh -c nslookup www.google.com" did not complete successfully: exit code: 1
------
 > [2/2] RUN nslookup www.google.com:
10.31 nslookup: can't connect to remote host: Address not available
------
Dockerfile:3
--------------------
   1 |     FROM alpine/curl
   2 |
   3 | >>> RUN nslookup www.google.com
   4 |
--------------------
error: failed to solve: process "/bin/sh -c nslookup www.google.com" did not complete successfully: exit code: 1

machine info:
Ubuntu 18.04.6
x86_64

cat /etc/resolv.conf on the Ubuntu machine:

nameserver 172.20.100.25
nameserver 172.20.100.27

the Ubuntu machine's network is perfectly fine.

cat /etc/resolv.conf in the container:

/ # cat /etc/resolv.conf
nameserver 127.0.0.11
options ndots:0

other steps：

• when i change step5's Dockerfile, RUN nslookup www.google.com to curl -vvvv -s https://www.google.com,it produce a similar error :

> [2/4] RUN curl -vvvv -s https://www.google.com:
0.223 * Could not resolve host: www.google.com
0.223 * shutting down connection #0

• when i run the step1-step6 on my own mac OS arm64, it works fine, no error.

---

so, why the build command failed？
Did i missed some config in the step 1?

[alazalazalaz]

update.
I added network_mode:bridge in step1, partial RUN command works fun now, such as nslookup wget apt.
The curl command still failed, error :
curl: (6) Could not resolve host: www.google.com