podman: Uninformative `slirp4netns` ERROR when portmapping

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

/kind bug

Description

Running unprivileged (rootless) container on ArchLinux (using dnsmasq and shorewall) gives uninformative ERRO[0006] slirp4netns failed. Same operation as root works.

Steps to reproduce the issue:

1. Install podman.

2. Pull alpine: podman pull alpine

3. Run container while portmapping docker-equivalently: podman run -d --log-level=debug -p 127.0.0.1:8787:8787 docker.io/library/alpine

Describe the results you received: See the attached (podman.log) output of podman run -d --log-level=debug -p 127.0.0.1:8787:8787 docker.io/library/alpine 2> /tmp/podman.log: container fails with non-descript slirp4netns error.

Describe the results you expected: Container starts with port forwarding to localhost.

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

Output of podman version:

Version:            1.1.2
RemoteAPI Version:  1
Go Version:         go1.12
Built:              Fri Mar  8 10:39:55 2019
OS/Arch:            linux/amd64

Output of podman info --debug:

debug:
  compiler: gc
  git commit: ""
  go version: go1.12
  podman version: 1.1.2
host:
  BuildahVersion: 1.7.1
  Conmon:
    package: Unknown
    path: /usr/bin/conmon
    version: 'conmon version , commit: 8fba206232c249a8fc4e2fac1469fb2fddbf5cf7'
  Distribution:
    distribution: arch
    version: unknown
  MemFree: 56151654400
  MemTotal: 67480981504
  OCIRuntime:
    package: Unknown
    path: /usr/bin/runc
    version: |-
      runc version 1.0.0-rc6
      commit: ccb5efd37fb7c86364786e9137e22948751de7ed-dirty
      spec: 1.0.1-dev
  SwapFree: 64135098368
  SwapTotal: 64135098368
  arch: amd64
  cpus: 8
  hostname: KI-P0695
  kernel: 5.0.4-arch1-1-ARCH
  os: linux
  rootless: true
  uptime: 5h 33m 35.72s (Approximately 0.21 days)
insecure registries:
  registries: []
registries:
  registries:
  - docker.io
  - registry.fedoraproject.org
  - quay.io
  - registry.access.redhat.com
  - registry.centos.org
store:
  ConfigFile: /home/balin/.config/containers/storage.conf
  ContainerStore:
    number: 43
  GraphDriverName: vfs
  GraphOptions: null
  GraphRoot: /home/balin/.local/share/containers/storage
  GraphStatus: {}
  ImageStore:
    number: 3
  RunRoot: /run/user/1000
  VolumePath: /home/balin/.local/share/containers/storage/volumes

Additional environment details (AWS, VirtualBox, physical, etc.): ArchLinux with dnsmasq local dns caching and shorewall running - eqivalent docker install uses dedicated bridge. How does podman handled this? Can’t find info in debugging this networking(?) problem.