instruction: Create a Dockerfile for networking
output: ```dockerfile
  from daemon: driver failed programming external connectivity on endpoint focused_swanson (9e2e139a9d8fc92b37c36edfa6214a6e986fa2028c0cc359812f685173fa6df7): Error starting userland proxy: error while calling PortManager.AddPort(): cannot expose privileged port 80, you might need to add "net.ipv4.ip_unprivileged_port_start=0" (currently 1024) to /etc/sysctl.conf, or set CAP_NET_BIND_SERVICE on rootlesskit binary, or choose a larger port number (>= 1024): listen tcp 0.0.0.0:80: bind: permission denied.
  When you experience this error, consider using an unprivileged port instead. For example, 8080 instead of 80.
  
  $ docker run -p 8080:80 nginx:alpine
  To allow exposing privileged ports, see Exposing privileged ports.Ping doesn't workPing does not work when /proc/sys/net/ipv4/ping_group_range is set to 1 0:
  
  $ cat /proc/sys/net/ipv4/ping_group_range
  1 0
  For details, see Routing ping packets.IPAddress shown in docker inspect is unreachableThis is an expected behavior, as the daemon is namespaced inside RootlessKit's
  network namespace. Use docker run -p instead.--net=host doesn't listen ports on the host network namespaceThis is an expected behavior, as the daemon is namespaced inside RootlessKit's
  network namespace. Use docker run -p instead.Network is slowDocker with rootless mode uses slirp4netns as the default network stack if slirp4netns v0.4.0 or later is installed.
  If slirp4netns is not installed, Docker falls back to VPNKit.
  Installing slirp4netns may improve the network throughput.For more information about network drivers for RootlessKit, see
  RootlessKit documentation.Also, changing MTU value may improve the throughput.
  The MTU value can be specified by creating ~/.config/systemd/user/docker.service.d/override.conf with the following content:
  
  [Service]
  Environment="DOCKERD_ROOTLESS_ROOTLESSKIT_MTU=<INTEGER>"And then restart the daemon:
  
  $ systemctl --user daemon-reload
  $ systemctl --user restart docker
  docker run -p does not propagate source IP addressesThis is because Docker in rootless mode uses RootlessKit's builtin port
  driver by default, which doesn't support source IP propagation. To enable
  source IP propagation, you can:Use the slirp4netns RootlessKit port driverUse the pasta RootlessKit network driver, with the implicit port driverThe pasta network driver is experimental, but provides improved throughput
  performance compared to the slirp4netns port driver. The pasta driver
  requires Docker Engine version 25.0 or later.To change the RootlessKit networking configuration:Create a file at ~/.config/systemd/user/docker.service.d/override.conf.Add the following contents, depending on which configuration you would like to use:slirp4netns
  
  [Service]
  Environment="DOCKERD_ROOTLESS_ROOTLESSKIT_NET=slirp4netns"
  Environment="DOCKERD_ROOTLESS_ROOTLESSKIT_PORT_DRIVER=slirp4netns"pasta network driver with implicit port driver
  
  [Service]
  Environment="DOCKERD_ROOTLESS_ROOTLESSKIT_NET=pasta"
  Environment="DOCKERD_ROOTLESS_ROOTLESSKIT_PORT_DRIVER=implicit"Restart the daemon:
  
  $ systemctl --user daemon-reload
  $ systemctl --user restart docker
  For more information about networking options for RootlessKit, see:Network driversPort driversTips for debuggingEntering into dockerd namespacesThe dockerd-rootless.sh script executes dockerd in its own user, mount, and network namespaces.For debugging, you can enter the namespaces by running
  nsenter -U --preserve-credentials -n -m -t $(cat $XDG_RUNTIME_DIR/docker.pid).
  Request changesTable of contentsHow it worksPrerequisitesDistribution-specific hintKnown limitationsInstallUninstallUsageDaemonClientBest practicesRootless Docker in DockerExpose Docker API socket through TCPExpose Docker API socket through SSHRouting ping packetsExposing privileged portsLimiting resourcesTroubleshootingUnable to install with systemd when systemd is present on the systemErrors when starting the Docker daemondocker pull errorsdocker run errorsNetworking errorsTips for debugging
  
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