resolv.rb: close socket

* lib/resolv.rb (UnconnectedUDP#lazy_initialize): store new
  sockets before binding, so the sockets get closed when the
  requester is closing.

* lib/resolv.rb (ConnectedUDP#lazy_initialize): ditto.

* lib/resolv.rb (UnconnectedUDP#close): synchronize to get rid of
  race condition.

* lib/resolv.rb (ConnectedUDP#close): ditto.

[ruby-core:85901] [Bug #14571]

From: quixoten (Devin Christensen) <quixoten@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62671 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/resolv.rb

@@ -732,9 +732,17 @@ class Resolv
         def initialize(*nameserver_port)
           super()
           @nameserver_port = nameserver_port
+          @initialized = false
+          @mutex = Thread::Mutex.new
+        end
+
+        def lazy_initialize
+          @mutex.synchronize {
+            next if @initialized
+            @initialized = true
             @socks_hash = {}
             @socks = []
-          nameserver_port.each {|host, port|
+            @nameserver_port.each {|host, port|
               if host.index(':')
                 bind_host = "::"
                 af = Socket::AF_INET6
@@ -748,19 +756,23 @@ class Resolv
               rescue Errno::EAFNOSUPPORT
                 next # The kernel doesn't support the address family.
               end
-            sock.do_not_reverse_lookup = true
-            DNS.bind_random_port(sock, bind_host)
               @socks << sock
               @socks_hash[bind_host] = sock
+              sock.do_not_reverse_lookup = true
+              DNS.bind_random_port(sock, bind_host)
             }
+          }
+          self
         end
 
         def recv_reply(readable_socks)
+          lazy_initialize
           reply, from = readable_socks[0].recvfrom(UDPSize)
           return reply, [from[3],from[1]]
         end
 
         def sender(msg, data, host, port=Port)
+          lazy_initialize
           sock = @socks_hash[host.index(':') ? "::" : "0.0.0.0"]
           return nil if !sock
           service = [host, port]
@@ -772,10 +784,15 @@ class Resolv
         end
 
         def close
+          @mutex.synchronize {
+            if @initialized
               super
               @senders.each_key {|service, id|
                 DNS.free_request_id(service[0], service[1], id)
               }
+              @initialized = false
+            end
+          }
         end
 
         class Sender < Requester::Sender # :nodoc:
@@ -798,20 +815,32 @@ class Resolv
           super()
           @host = host
           @port = port
-          is_ipv6 = host.index(':')
+          @mutex = Thread::Mutex.new
+          @initialized = false
+        end
+
+        def lazy_initialize
+          @mutex.synchronize {
+            next if @initialized
+            @initialized = true
+            is_ipv6 = @host.index(':')
             sock = UDPSocket.new(is_ipv6 ? Socket::AF_INET6 : Socket::AF_INET)
             @socks = [sock]
             sock.do_not_reverse_lookup = true
             DNS.bind_random_port(sock, is_ipv6 ? "::" : "0.0.0.0")
-          sock.connect(host, port)
+            sock.connect(@host, @port)
+          }
+          self
         end
 
         def recv_reply(readable_socks)
+          lazy_initialize
           reply = readable_socks[0].recv(UDPSize)
           return reply, nil
         end
 
         def sender(msg, data, host=@host, port=@port)
+          lazy_initialize
           unless host == @host && port == @port
             raise RequestError.new("host/port don't match: #{host}:#{port}")
           end
@@ -822,10 +851,15 @@ class Resolv
         end
 
         def close
+          @mutex.synchronize do
+            if @initialized
               super
               @senders.each_key {|from, id|
                 DNS.free_request_id(@host, @port, id)
               }
+              @initialized = false
+            end
+          end
         end
 
         class Sender < Requester::Sender # :nodoc:
@@ -839,6 +873,7 @@ class Resolv
 
       class MDNSOneShot < UnconnectedUDP # :nodoc:
         def sender(msg, data, host, port=Port)
+          lazy_initialize
           id = DNS.allocate_request_id(host, port)
           request = msg.encode
           request[0,2] = [id].pack('n')
@@ -848,6 +883,7 @@ class Resolv
         end
 
         def sender_for(addr, msg)
+          lazy_initialize
           @senders[msg.id]
         end
       end

test/resolv/test_dns.rb

@@ -3,6 +3,7 @@ require 'test/unit'
 require 'resolv'
 require 'socket'
 require 'tempfile'
+require 'minitest/mock'
 
 class TestResolvDNS < Test::Unit::TestCase
   def setup
@@ -246,4 +247,22 @@ class TestResolvDNS < Test::Unit::TestCase
     }
     assert_operator(2**14, :<, m.to_s.length)
   end
+
+  def assert_no_fd_leak
+    socket = assert_throw(self) do |tag|
+      Resolv::DNS.stub(:bind_random_port, ->(s, *) {throw(tag, s)}) do
+        yield.getname("8.8.8.8")
+      end
+    end
+
+    assert_predicate(socket, :closed?, "file descriptor leaked")
+  end
+
+  def test_no_fd_leak_connected
+    assert_no_fd_leak {Resolv::DNS.new(nameserver_port: [['127.0.0.1', 53]])}
+  end
+
+  def test_no_fd_leak_unconnected
+    assert_no_fd_leak {Resolv::DNS.new}
+  end
 end