Podman 3.3 adds 127.0.0.1 /etc/hosts record for hostname, breaking gethostbyaddr for the hostname #11596

adelton · 2021-09-15T18:26:32Z

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

The change for #10319 via #11118 changed the /etc/hosts entry being added from 127.0.1.1 to 127.0.0.1. That in turn breaks gethostbyaddr in the container, at least in rootless pods.

Steps to reproduce the issue:

podman pod create --name test-hostname --hostname machine.example.test --add-host machine.example.test:172.29.0.1
podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 cat /etc/hosts
podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 python3 -c 'import socket; print(socket.gethostbyaddr("machine.example.test"))'

Describe the results you received:

$ podman pod create --name test-hostname --hostname machine.example.test --add-host machine.example.test:172.29.0.1
be4669ba40ba018668c5aa057299f70328a3cdc9b9326b79a041ccdf4121b4ea
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.29.0.1 machine.example.test
# used by slirp4netns
10.0.2.100	machine.example.test be4669ba40ba-infra
10.0.2.2 host.containers.internal
127.0.0.1 machine.example.test cranky_ritchie
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 python3 -c 'import socket; print(socket.gethostbyaddr("machine.example.test"))'
('localhost', ['localhost.localdomain', 'localhost4', 'localhost4.localdomain4'], ['127.0.0.1'])

Describe the results you expected:

$ podman pod create --name test-hostname --hostname machine.example.test --add-host machine.example.test:172.29.0.1
40b60852dfd48d40ff084d230572dd33c3fcf72ad8efc57a54aa42af98ef5a62
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.29.0.1 machine.example.test
# used by slirp4netns
10.0.2.100	machine.example.test 40b60852dfd4-infra
10.0.2.2 host.containers.internal
127.0.1.1 machine.example.test brave_nightingale
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 python3 -c 'import socket; print(socket.gethostbyaddr("machine.example.test"))'
('machine.example.test', ['brave_nightingale'], ['127.0.1.1'])

Additional information you deem important (e.g. issue happens only occasionally):

This is a regression with podman-3.3.1-1.fc34.x86_64, against podman-3.2.3-1.fc34.x86_64.

Now the previous behaviour which returned 127.0.1.1 was not great either but at least the hostname returned was the actual container hostname, not localhost.

Output of podman version:

Version:      3.3.1
API Version:  3.3.1
Go Version:   go1.16.6
Built:        Mon Aug 30 22:46:36 2021
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.22.3
  cgroupControllers: []
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-2.0.29-2.fc34.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.29, commit: '
  cpus: 2
  distribution:
    distribution: fedora
    version: "34"
  eventLogger: journald
  hostname: kvm-01-guest16.lab.eng.brq.redhat.com
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.13.15-200.fc34.x86_64
  linkmode: dynamic
  memFree: 5698027520
  memTotal: 8326172672
  ociRuntime:
    name: crun
    package: crun-1.0-1.fc34.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 1.0
      commit: 139dc6971e2f1d931af520188763e984d6cdfbf8
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /run/user/1000/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: true
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.1.12-2.fc34.x86_64
    version: |-
      slirp4netns version 1.1.12
      commit: 7a104a101aa3278a2152351a082a6df71f57c9a3
      libslirp: 4.4.0
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.0
  swapFree: 8325689344
  swapTotal: 8325689344
  uptime: 10h 17m 58.67s (Approximately 0.42 days)
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - docker.io
  - quay.io
store:
  configFile: /home/test/.config/containers/storage.conf
  containerStore:
    number: 4
    paused: 0
    running: 4
    stopped: 0
  graphDriverName: overlay
  graphOptions: {}
  graphRoot: /home/test/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: btrfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 88
  runRoot: /run/user/1000/containers
  volumePath: /home/test/.local/share/containers/storage/volumes
version:
  APIVersion: 3.3.1
  Built: 1630356396
  BuiltTime: Mon Aug 30 22:46:36 2021
  GitCommit: ""
  GoVersion: go1.16.6
  OsArch: linux/amd64
  Version: 3.3.1

Package info (e.g. output of rpm -q podman or apt list podman):

podman-3.3.1-1.fc34.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/master/troubleshooting.md)

Yes (latest packaged in Fedora 34).

Additional environment details (AWS, VirtualBox, physical, etc.):

A Fedora 34 VM.

The text was updated successfully, but these errors were encountered:

rhatdan · 2021-09-15T19:11:08Z

@Luap99 @mheon PTAL

Luap99 · 2021-09-16T09:57:48Z

OK so I think the problem here is that our logic thinks joining the pod namespace is the same as the none networking mode.

I think we should never add 127.0.1.1 or 127.0.0.1 in case of joining the pod ns. @adelton Do you agree?

Edit: This is the result I get when 127... is not added.

$ bin/podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 python3 -c 'import socket; print(socket.gethostbyaddr("machine.example.test"))'
('machine.example.test', ['d6fd0f0ae175-infra'], ['10.0.2.100'])

adelton · 2021-09-16T10:26:24Z

Yes, this looks like a good improvement.

The check for net=none was wrong. It just assumed when we do not create the netns but have one set that we use the none mode. This however also applies to a container which joins the pod netns. To correctly check for the none mode use `config.NetMode.IsNone()`. Fixes containers#11596 Signed-off-by: Paul Holzinger <[email protected]>

adelton · 2021-10-18T11:56:30Z

I see the fix should be in podman 3.4 but https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_21.04/ still has only 3.3.1. Is there any plan to build 3.4 there?

mheon · 2021-10-18T19:24:57Z

@lsm5 PTAL

…ution." This reverts commit 7699cbc. Issue containers/podman#11596 was fixed in podman 3.4.

Luap99 · 2022-04-20T11:13:43Z

@adelton FYI I tested this with my new /etc/hosts changes from #13918

The result I now get is ('machine.example.test', [], ['172.29.0.1']) which I assume works for you?
Basically the new logic makes sure to never overwrite entries that a user added with --add-host.

adelton · 2022-04-20T12:56:46Z

With podman-3.4.4-1.fc35.x86_64 I get

$ podman pod create --name test-hostname --hostname machine.example.test --add-host machine.example.test:172.29.0.1
01f31527cd44dc95468e48352c0799891e41f2ea13e92982b6468adaee94b1de
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.29.0.1 machine.example.test
# used by slirp4netns
10.0.2.100	machine.example.test 01f31527cd44-infra
10.0.2.2 host.containers.internal
$ podman run --rm --pod test-hostname registry.fedoraproject.org/fedora:34 python3 -c 'import socket; print(socket.gethostbyaddr("machine.example.test"))'
('machine.example.test', ['01f31527cd44-infra'], ['10.0.2.100'])

I don't see a problem with the IP address being different as long as the hostname is the expected one.

openshift-ci bot added the kind/bug Categorizes issue or PR as related to a bug. label Sep 15, 2021

adelton mentioned this issue Sep 15, 2021

podman-3.3.0 - Changes to default /etc/hosts handling are breaking container workloads #11282

Closed

Luap99 mentioned this issue Sep 16, 2021

Only add 127.0.0.1 entry to /etc/hosts with --net=none #11605

Merged

openshift-merge-robot closed this as completed in #11605 Sep 16, 2021

douglas-legulas mentioned this issue Oct 17, 2021

Regression 3.4: missing entries in /etc/hosts #12003

Closed

adelton added a commit to adelton/freeipa-container that referenced this issue Dec 31, 2021

Revert "With podman 3.3, rootless pod setup has broken hostname resol…

0777523

…ution." This reverts commit 7699cbc. Issue containers/podman#11596 was fixed in podman 3.4.

github-actions bot added the locked - please file new issue/PR Assist humans wanting to comment on an old issue or PR with locked comments. label Sep 20, 2023

github-actions bot locked as resolved and limited conversation to collaborators Sep 20, 2023

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Podman 3.3 adds 127.0.0.1 /etc/hosts record for hostname, breaking gethostbyaddr for the hostname #11596

Podman 3.3 adds 127.0.0.1 /etc/hosts record for hostname, breaking gethostbyaddr for the hostname #11596

adelton commented Sep 15, 2021

rhatdan commented Sep 15, 2021

Luap99 commented Sep 16, 2021 •

edited

Loading

adelton commented Sep 16, 2021

adelton commented Oct 18, 2021

mheon commented Oct 18, 2021

Luap99 commented Apr 20, 2022

adelton commented Apr 20, 2022

Podman 3.3 adds 127.0.0.1 /etc/hosts record for hostname, breaking gethostbyaddr for the hostname #11596

Podman 3.3 adds 127.0.0.1 /etc/hosts record for hostname, breaking gethostbyaddr for the hostname #11596

Comments

adelton commented Sep 15, 2021

rhatdan commented Sep 15, 2021

Luap99 commented Sep 16, 2021 • edited Loading

adelton commented Sep 16, 2021

adelton commented Oct 18, 2021

mheon commented Oct 18, 2021

Luap99 commented Apr 20, 2022

adelton commented Apr 20, 2022

Luap99 commented Sep 16, 2021 •

edited

Loading