Class: OsCtl::ExportFS::Operations::Server::Spawn

Inherits:
Base
  • Object
show all
Includes:
Lib::Utils::Log, Lib::Utils::System
Defined in:
lib/osctl/exportfs/operations/server/spawn.rb

Overview

Start a NFS server and wait for it to terminate

Networking is realized using a pair of veth interfaces – one on the host and one in the container. IP addresses of the NFS server is routed to the container, the container routes outbound traffic through osrtr0.

The container has its own mount, network, UTS and PID namespace, only the user namespace is shared. The rootfs is a tmpfs and all required directories and files are bind-mounted from the host, i.e. the entire /nix/store, static files in /etc and so on. All other mounts are cleared.

Constant Summary collapse

SYSTEM_PROFILE = 
'/nix/var/nix/profiles/system'.freeze
SYSTEM_PATH = 
'/run/current-system/sw/bin'.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Base

run

Constructor Details

#initialize(name) ⇒ Spawn

Returns a new instance of Spawn.

Parameters:

  • name (String) 


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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 25

def initialize(name)
  super()
  @server = Server.new(name)
  @cfg = server.open_config
  @cgroup = Operations::Server::CGroup.new(server)
  @sys = OsCtl::Lib::Sys.new
end

Instance Attribute Details

#cfg ⇒ Object (readonly, protected)

Returns the value of attribute cfg.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def cfg
  @cfg
end

#cgroup ⇒ Object (readonly, protected)

Returns the value of attribute cgroup.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def cgroup
  @cgroup
end

#netif_host ⇒ Object (readonly, protected)

Returns the value of attribute netif_host.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def netif_host
  @netif_host
end

#netif_ns ⇒ Object (readonly, protected)

Returns the value of attribute netif_ns.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def netif_ns
  @netif_ns
end

#rand_id ⇒ Object (readonly, protected)

Returns the value of attribute rand_id.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def rand_id
  @rand_id
end

#server ⇒ Object (readonly, protected)

Returns the value of attribute server.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def server
  @server
end

#sys ⇒ Object (readonly, protected)

Returns the value of attribute sys.



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 98

def sys
  @sys
end

Instance Method Details

#add_exports ⇒ Object (protected) 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 272

def add_exports
  cfg.exports.group_by_as.each do |dir, as, _exports|
    target_as = File.join(RunState::ROOTFS, as)

    FileUtils.mkdir_p(target_as)
    sys.bind_mount(dir, target_as)
  end
end

#clear_mounts ⇒ Object (protected) 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 209

def clear_mounts
  mounts = []
  whitelist = %W[
    /
    /dev
    /nix/store
    /nix/.overlay-store
    /run
    #{RunState::ROOTFS}
    #{RunState::ROOTFS}/**
    #{RunState::SERVERS}/*/shared
    /run/wrappers
    /sys
    /sys/fs/cgroup
    /sys/fs/cgroup/*
  ]

  File.open('/proc/mounts').each_line do |line|
    fs, mountpoint = line.split

    keep = whitelist.detect do |pattern|
      File.fnmatch?(pattern, mountpoint)
    end

    mounts << mountpoint unless keep
  end

  mounts.sort.reverse_each do |mnt|
    sys.unmount_lazy(mnt)
  rescue Errno::ENOENT
    next
  end
end

#execute ⇒ Object 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 33

def execute
  server.synchronize do
    raise 'server is already running' if server.running?
    raise 'provide server address' if cfg.address.nil?
  end

  @rand_id = SecureRandom.hex(3)
  netns = rand_id
  @netif_host = cfg.netif
  @netif_ns = "nfsns-#{server.name}"

  cgroup.enter_manager

  # The parent remains in the host namespace, where as the child unshares
  # namespaces
  main = Process.fork do
    cgroup.enter_payload
    Process.setpgrp

    # Create a new network namespace and a veth pair
    syscmd("ip netns add #{netns}")
    syscmd("ip link add #{netif_host} type veth peer name #{netif_ns}")
    syscmd("ip link set #{netif_ns} netns #{netns}")
    syscmd("ip link set #{netif_host} up")
    syscmd("ip route add #{cfg.address}/32 dev #{netif_host}")

    # Remove the named network namespace from the filesystem
    sys.setns_path("/run/netns/#{netns}", OsCtl::Lib::Sys::CLONE_NEWNET)
    sys.unmount("/run/netns/#{netns}")
    File.unlink("/run/netns/#{netns}")

    # Create new namespaces
    sys.unshare_ns(
      OsCtl::Lib::Sys::CLONE_NEWNS \
      | OsCtl::Lib::Sys::CLONE_NEWUTS \
      | OsCtl::Lib::Sys::CLONE_NEWIPC \
      | OsCtl::Lib::Sys::CLONE_NEWPID
    )

    # Run the server in a forked process, required by PID namespace
    run_server
  end

  # Forward SIGTERM and SIGINT
  %w[TERM INT].each do |sig|
    Signal.trap(sig) do
      Process.kill(sig, main)
    end
  end

  # Wait for the child to terminate and then cleanup
  _waited, status = Process.wait2(main)
  FileUtils.rm_f(server.pid_file)
  syscmd("ip link del #{netif_host}")

  log(:info, 'Killing remaining processes')
  cgroup.clear_payload

  return if status.success?

  raise "server spawn failed with exit status #{status.exitstatus || 1}"
end

#mount_nix_paths ⇒ Object (protected) 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 264

def mount_nix_paths
  sys.bind_mount('/nix/store', File.join(RunState::ROOTFS, 'nix/store'))
  sys.bind_mount_readonly(
    '/nix/var/nix/profiles',
    File.join(RunState::ROOTFS, 'nix/var/nix/profiles')
  )
end

#run_server ⇒ Object (protected) 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 100

def run_server
  main = Process.fork do
    # Mount the new root filesystem
    sys.mount_tmpfs(RunState::ROOTFS)

    # Add exports that were configured before the server was started
    add_exports

    # Mark all mounts as slave, in case some mounts from the parent namespace
    # are marked as shared, because unmounting them in this namespaces
    # would result in them being unmounted in the parent namespace as well.
    sys.make_rslave('/')

    # Unmount all unnecessary mounts
    clear_mounts

    # Create necessary directories in the new rootfs
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'bin'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'dev'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'etc/runit'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'proc'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, RunState::DIR))
    File.chmod(0o750, File.join(RunState::ROOTFS, RunState::DIR))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, RunState::CURRENT_SERVER))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'nix/store'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'nix/var/nix/profiles'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'sys'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'var/lib/nfs'))
    FileUtils.mkdir_p(File.join(RunState::ROOTFS, 'usr/bin'))

    # Mount /proc, /dev, /sys, /nix/store and system profiles
    sys.mount_proc(File.join(RunState::ROOTFS, 'proc'))
    sys.bind_mount('/dev', File.join(RunState::ROOTFS, 'dev'))
    mount_nix_paths
    sys.bind_mount('/sys', File.join(RunState::ROOTFS, 'sys'))

    setup_system_paths

    %w[group passwd shadow].each do |v|
      dst = File.join(RunState::ROOTFS, 'etc', v)
      File.new(dst, 'w').close
      sys.bind_mount(File.join('/etc', v), dst)
    end

    # Mount the current server directory, we need rbind to also mount the
    # shared directory
    sys.rbind_mount(
      server.dir,
      File.join(RunState::ROOTFS, RunState::CURRENT_SERVER)
    )

    # Switch to the new rootfs
    Dir.chdir(RunState::ROOTFS)
    Dir.mkdir('old-root')
    syscmd('pivot_root . old-root')
    sys.chroot('.')
    sys.unmount_lazy('/old-root')
    Dir.rmdir('/old-root')
    server.enter_ns

    # Mount files and directories from the server directory to the system
    # where they're expected
    sys.bind_mount(server.nfs_state, '/var/lib/nfs')
    File.symlink('/run', '/var/run')
    %w[hosts localtime services].each do |v|
      File.symlink("/etc/static/#{v}", "/etc/#{v}")
    end
    File.symlink(server.exports_file, '/etc/exports')

    # Generate runit scripts and services
    Operations::Runit::Generate.run(server, cfg)

    # Generate NFS exports
    Operations::Exportfs::Generate.run(server)

    # Configure the network interface
    syscmd('ip link set lo up')
    syscmd("ip link set #{netif_ns} name eth0")
    @netif_ns = 'eth0'
    syscmd("ip link set #{netif_ns} up")
    syscmd("ip addr add #{cfg.address}/32 dev #{netif_ns}")
    syscmd("ip route add 255.255.255.254 dev #{netif_ns}")
    syscmd("ip route add default via 255.255.255.254 dev #{netif_ns}")

    # Instruct runit to exit on SIGCONT
    if File.exist?('/etc/runit/stopit')
      File.chmod(0o100, '/etc/runit/stopit')
    else
      File.new('/etc/runit/stopit', 'w', 0o100).close
    end

    puts 'Starting nfsd...'
    Process.exec('runit-init')
  end

  # Save the server's PID file
  File.write(server.pid_file, main.to_s)

  # Forward SIGTERM and SIGINT
  %w[TERM INT].each do |sig|
    Signal.trap(sig) do
      Process.kill('CONT', main)
    end
  end

  _waited, status = Process.wait2(main)
  exit!(status.exitstatus || 1) unless status.success?
end

#setup_system_paths ⇒ Object (protected) 



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# File 'lib/osctl/exportfs/operations/server/spawn.rb', line 243

def setup_system_paths
  File.symlink(
    SYSTEM_PROFILE,
    File.join(RunState::ROOTFS, 'run/current-system')
  )
  File.symlink(
    File.join(SYSTEM_PATH, 'sh'),
    File.join(RunState::ROOTFS, 'bin/sh')
  )
  File.symlink(
    File.join(SYSTEM_PATH, 'env'),
    File.join(RunState::ROOTFS, 'usr/bin/env')
  )
  File.symlink(
    '/run/current-system/etc',
    File.join(RunState::ROOTFS, 'etc/static')
  )

  ENV['PATH'] = SYSTEM_PATH
end