Add support for Linux's abstract sockets (#2564)

* Support Linux's abstract sockets

Closes #2526

* Add two simple UNIXSocket tests

lib/puma.rb

@@ -39,6 +39,20 @@ def self.ssl?
     HAS_SSL
   end
 
+  def self.abstract_unix_socket?
+    @abstract_unix ||=
+      if HAS_UNIX_SOCKET
+        begin
+          ::UNIXServer.new("\0puma.temp.unix").close
+          true
+        rescue ArgumentError  # darwin
+          false
+        end
+      else
+        false
+      end
+  end
+
   # @!attribute [rw] stats_object=
   def self.stats_object=(val)
     @get_stats = val

lib/puma/binder.rb

@@ -177,11 +177,19 @@ def parse(binds, logger, log_msg = 'Listening')
           @listeners << [str, io] if io
         when "unix"
           path = "#{uri.host}#{uri.path}".gsub("%20", " ")
+          abstract = false
+          if str.start_with? 'unix://@'
+            raise "OS does not support abstract UNIXSockets" unless Puma.abstract_unix_socket?
+            abstract = true
+            path = "@#{path}"
+          end
 
           if fd = @inherited_fds.delete(str)
+            @unix_paths << path unless abstract
             io = inherit_unix_listener path, fd
             logger.log "* Inherited #{str}"
           elsif sock = @activated_sockets.delete([ :unix, path ])
+            @unix_paths << path unless abstract || File.exist?(path)
             io = inherit_unix_listener path, sock
             logger.log "* Activated #{str}"
           else
@@ -205,6 +213,7 @@ def parse(binds, logger, log_msg = 'Listening')
               end
             end
 
+            @unix_paths << path unless abstract || File.exist?(path)
             io = add_unix_listener path, umask, mode, backlog
             logger.log "* #{log_msg} on #{str}"
           end
@@ -355,8 +364,6 @@ def inherit_ssl_listener(fd, ctx)
     # Tell the server to listen on +path+ as a UNIX domain socket.
     #
     def add_unix_listener(path, umask=nil, mode=nil, backlog=1024)
-      @unix_paths << path unless File.exist? path
-
       # Let anyone connect by default
       umask ||= 0
 
@@ -373,8 +380,7 @@ def add_unix_listener(path, umask=nil, mode=nil, backlog=1024)
             raise "There is already a server bound to: #{path}"
           end
         end
-
-        s = UNIXServer.new(path)
+        s = UNIXServer.new path.sub(/\A@/, "\0") # check for abstract UNIXSocket
         s.listen backlog
         @ios << s
       ensure
@@ -393,8 +399,6 @@ def add_unix_listener(path, umask=nil, mode=nil, backlog=1024)
     end
 
     def inherit_unix_listener(path, fd)
-      @unix_paths << path unless File.exist? path
-
       s = fd.kind_of?(::TCPServer) ? fd : ::UNIXServer.for_fd(fd)
 
       @ios << s
@@ -407,24 +411,24 @@ def inherit_unix_listener(path, fd)
     end
 
     def close_listeners
-      listeners.each do |l, io|
-        io.close unless io.closed? # Ruby 2.2 issue
-        uri = URI.parse(l)
+      @listeners.each do |l, io|
+        io.close unless io.closed?
+        uri = URI.parse l
         next unless uri.scheme == 'unix'
         unix_path = "#{uri.host}#{uri.path}"
-        File.unlink unix_path if unix_paths.include? unix_path
+        File.unlink unix_path if @unix_paths.include?(unix_path) && File.exist?(unix_path)
       end
     end
 
     def redirects_for_restart
-      redirects = listeners.map { |a| [a[1].to_i, a[1].to_i] }.to_h
+      redirects = @listeners.map { |a| [a[1].to_i, a[1].to_i] }.to_h
       redirects[:close_others] = true
       redirects
     end
 
     # @version 5.0.0
     def redirects_for_restart_env
-      listeners.each_with_object({}).with_index do |(listen, memo), i|
+      @listeners.each_with_object({}).with_index do |(listen, memo), i|
         memo["PUMA_INHERIT_#{i}"] = "#{listen[1].to_i}:#{listen[0]}"
       end
     end

lib/puma/control_cli.rb

@@ -176,7 +176,9 @@ def send_request
         when 'tcp'
           TCPSocket.new uri.host, uri.port
         when 'unix'
-          UNIXSocket.new "#{uri.host}#{uri.path}"
+          # check for abstract UNIXSocket
+          UNIXSocket.new(@control_url.start_with?('unix://@') ?
+            "\0#{uri.host}#{uri.path}" : "#{uri.host}#{uri.path}")
         else
           raise "Invalid scheme: #{uri.scheme}"
         end

test/test_pumactl.rb

@@ -175,6 +175,30 @@ def test_control_ssl
     assert_kind_of Thread, t.join, "server didn't stop"
   end
 
+  def test_control_aunix
+    skip_unless :aunix
+
+    url = "unix://@test_control_aunix.unix"
+
+    opts = [
+      "--control-url", url,
+      "--control-token", "ctrl",
+      "--config-file", "test/config/app.rb",
+    ]
+
+    control_cli = Puma::ControlCLI.new (opts + ["start"]), @ready, @ready
+    t = Thread.new do
+      control_cli.run
+    end
+
+    wait_booted
+
+    assert_command_cli_output opts + ["status"], "Puma is started"
+    assert_command_cli_output opts + ["stop"], "Command stop sent success"
+
+    assert_kind_of Thread, t.join, "server didn't stop"
+  end
+
   private
 
   def assert_command_cli_output(options, expected_out)

test/test_unix_socket.rb

@@ -8,21 +8,21 @@ class TestPumaUnixSocket < Minitest::Test
 
   App = lambda { |env| [200, {}, ["Works"]] }
 
-  def setup
-    return unless UNIX_SKT_EXIST
-    @tmp_socket_path = tmp_path('.sock')
+  def teardown
+    return if skipped?
+    @server.stop(true)
+  end
+
+  def server_unix(type)
+    @tmp_socket_path = type == :unix ? tmp_path('.sock') : "@TestPumaUnixSocket"
     @server = Puma::Server.new App
     @server.add_unix_listener @tmp_socket_path
     @server.run
   end
 
-  def teardown
-    return unless UNIX_SKT_EXIST
-    @server.stop(true)
-  end
-
-  def test_server
+  def test_server_unix
     skip_unless :unix
+    server_unix :unix
     sock = UNIXSocket.new @tmp_socket_path
 
     sock << "GET / HTTP/1.0\r\nHost: blah.com\r\n\r\n"
@@ -31,4 +31,16 @@ def test_server
 
     assert_equal expected, sock.read(expected.size)
   end
+
+  def test_server_aunix
+    skip_unless :aunix
+    server_unix :aunix
+    sock = UNIXSocket.new @tmp_socket_path.sub(/\A@/, "\0")
+
+    sock << "GET / HTTP/1.0\r\nHost: blah.com\r\n\r\n"
+
+    expected = "HTTP/1.0 200 OK\r\nContent-Length: 5\r\n\r\nWorks"
+
+    assert_equal expected, sock.read(expected.size)
+  end
 end