How to setup internal and external networking for rootless containers with podman

Question

I am trying to get networking working with rootless containers using podman. Getting either external networking up and running or internal networking is not the issue. Using the --network option, containers are able to see each other. However ping 8.8.8.8 does not work. Starting containers without --network or with --network=slirp4netns ping 8.8.8.8 does work as expected. Of course in the latter case, there is no internal networking. What I think this tells me is that host is not blocking external access from within containers. The issues that I am facing is that I seem to be unable to get both internal and external networking working within containers at the same time.

> podman network ls 
NETWORK ID    NAME           VERSION     PLUGINS
2f259bab93aa  podman         0.4.0       bridge,portmap,firewall,tuning
6129a34887d3  container-net  0.4.0       bridge,portmap,firewall,tuning,dnsname

I am starting containers like so:

podman pod create \
  --network container-net \
  --network-alias test-pod \
  --hostname test-01 \
  --name test-pod

Contents of start-test.sh:

podman run --rm -it \
  --pod test-pod \
  --network=container-net \
  --dns-search dns.podman \
  --name test-01 \
  --network-alias test-01 \
  docker.io/alpine /bin/sh

> ./start-test.sh 
/ # ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
^C
--- 8.8.8.8 ping statistics ---
5 packets transmitted, 0 packets received, 100% packet loss

> podman --version
podman version 3.3.1

I have checked that selinux is not the cause by test with: setenforce 0 as well.

Is it possible to get both internal and external networking working within containers and if so, what does one need to do?

fatherlinux · Accepted Answer · 2021-10-21 17:36:23Z

1

I just tried this on RHEL 8 and I was able to reproduce this issue. We also figured out the issue (I think). Try the following:

sudo sysctl -w net.ipv4.ping_group_range="0 2147483647"

You might be being limited by the group range and /etc/subuid /etc/subgid:

https://man7.org/linux/man-pages/man7/icmp.7.html

I'm not sure what the long term solution is yet, but if this works, you can likely fix it with sysctl for now.

answered Oct 21, 2021 at 17:36

fatherlinux

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Gerben Venekamp · Accepted Answer · 2021-10-27 19:52:24Z

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The issue I was having was not related to any configuration. As it turned out after having removed all podman created networks, rebooting the machine and recreating the networks I needed, the containers behave as expected, i.e. internal and external networking are working.

answered Oct 27, 2021 at 19:52

Gerben Venekamp

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1 Comment

akostadinov Over a year ago

how to remove the default network??

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