/etc/hosts has wrong content

[mlegenovic]

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

/kind bug

Description

If container is started with --network=host /etc/hosts maps hostname to wrong IP address (127.0.1.1).

Steps to reproduce the issue:

1. podman run -it --rm --network host registry.fedoraproject.org/fedora:34 cat /etc/hosts

Describe the results you received:

podman run -it --rm --network host 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
127.0.1.1 foo.mydomain.com foo.mydomain.com optimistic_newton

Describe the results you expected:

podman run -it --rm --network host 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
192.168.1.72 foo.mydomain.com foo.mydomain.com optimistic_newton

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

Output of podman version:

Version:      3.2.3
API Version:  3.2.3
Go Version:   go1.16.5
Built:        Fri Jul 16 22:33:32 2021
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.21.3
  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: 8
  distribution:
    distribution: fedora
    version: "34"
  eventLogger: journald
  hostname: foo.mydomain.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: 5.13.4-200.fc34.x86_64
  linkmode: dynamic
  memFree: 29542653952
  memTotal: 33589002240
  ociRuntime:
    name: crun
    package: crun-0.20.1-1.fc34.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 0.20.1
      commit: 0d42f1109fd73548f44b01b3e84d04a279e99d2e
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    exists: true
    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-1.1.9-1.fc34.x86_64
    version: |-
      slirp4netns version 1.1.8+dev
      commit: 6dc0186e020232ae1a6fcc1f7afbc3ea02fd3876
      libslirp: 4.4.0
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.0
  swapFree: 8589930496
  swapTotal: 8589930496
  uptime: 21m 22.51s
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - docker.io
  - quay.io
store:
  configFile: /home/test/.config/containers/storage.conf
  containerStore:
    number: 1
    paused: 0
    running: 0
    stopped: 1
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: fuse-overlayfs-1.5.0-1.fc34.x86_64
      Version: |-
        fusermount3 version: 3.10.4
        fuse-overlayfs: version 1.5
        FUSE library version 3.10.4
        using FUSE kernel interface version 7.31
  graphRoot: /home/test/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: xfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 10
  runRoot: /run/user/1000/containers
  volumePath: /home/test/.local/share/containers/storage/volumes
version:
  APIVersion: 3.2.3
  Built: 1626467612
  BuiltTime: Fri Jul 16 22:33:32 2021
  GitCommit: ""
  GoVersion: go1.16.5
  OsArch: linux/amd64
  Version: 3.2.3

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

podman-3.2.3-1.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

Version:      3.3.0-dev
API Version:  3.3.0-dev
Go Version:   go1.16.5
Git Commit:   d7b2f03f8a5d0e3789ac185ea03989463168fb76
Built:        Tue Jul 27 13:20:19 2021
OS/Arch:      linux/amd64

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

[Luap99]

Why would you need 192.168.1.72 as entry in /etc/hosts? Is this your eth0 ip address? I do not think podman can figure out the correct ip. You could have several interfaces with several ip adresses. According to the hosts man page:

127.0.1.1 is often used for the FQDN of the machine

I close this as duplicate of #10319.

[mlegenovic]

To be honest, I was sure there is an issue on this topic, but I couldn't find it.

My description what I expect is wrong, I'm not expecting any IP address in /etc/hosts file if --network=host is passed as argument, also not 127.0.1.1. Problem with this entry is that a service as consequence starts listening on 127.0.1.1, and this is wrong. In docker, if you run hostname -i in container which is started with --network=host you are getting the same IP address like on host machine. Podman returns now 127.0.1.1, but this was not the case in older version (on RHEL 7).

The problem came to light when a developer in our company complained that he could no longer connect to a service from a remote machine (after upgrade to RHEL 8). netstat -tulpen showed where the problem is: 127.0.1.1:7105, so you can access the service from local machine, but not from remote.