Merge pull request #2662 from sonalkr132/ipv6-fallback

Fallback to IPv4 when IPv6 is unreachable

(cherry picked from commit 533a242)

Author: simi

Manifest.txt

@@ -354,6 +354,7 @@ lib/rubygems/config_file.rb
 lib/rubygems/core_ext/kernel_gem.rb
 lib/rubygems/core_ext/kernel_require.rb
 lib/rubygems/core_ext/kernel_warn.rb
+lib/rubygems/core_ext/tcpsocket_init.rb
 lib/rubygems/defaults.rb
 lib/rubygems/dependency.rb
 lib/rubygems/dependency_installer.rb

lib/rubygems/config_file.rb

@@ -45,6 +45,7 @@ class Gem::ConfigFile
   DEFAULT_UPDATE_SOURCES = true
   DEFAULT_CONCURRENT_DOWNLOADS = 8
   DEFAULT_CERT_EXPIRATION_LENGTH_DAYS = 365
+  DEFAULT_IPV4_FALLBACK_ENABLED = false
 
   ##
   # For Ruby packagers to set configuration defaults.  Set in
@@ -140,6 +141,12 @@ class Gem::ConfigFile
 
   attr_accessor :cert_expiration_length_days
 
+  ##
+  # == Experimental ==
+  # Fallback to IPv4 when IPv6 is not reachable or slow (default: false)
+
+  attr_accessor :ipv4_fallback_enabled
+
   ##
   # Path name of directory or file of openssl client certificate, used for remote https connection with client authentication
 
@@ -175,6 +182,7 @@ def initialize(args)
     @update_sources = DEFAULT_UPDATE_SOURCES
     @concurrent_downloads = DEFAULT_CONCURRENT_DOWNLOADS
     @cert_expiration_length_days = DEFAULT_CERT_EXPIRATION_LENGTH_DAYS
+    @ipv4_fallback_enabled = ENV['IPV4_FALLBACK_ENABLED'] == 'true' || DEFAULT_IPV4_FALLBACK_ENABLED
 
     operating_system_config = Marshal.load Marshal.dump(OPERATING_SYSTEM_DEFAULTS)
     platform_config = Marshal.load Marshal.dump(PLATFORM_DEFAULTS)
@@ -203,6 +211,7 @@ def initialize(args)
     @disable_default_gem_server  = @hash[:disable_default_gem_server]  if @hash.key? :disable_default_gem_server
     @sources                     = @hash[:sources]                     if @hash.key? :sources
     @cert_expiration_length_days = @hash[:cert_expiration_length_days] if @hash.key? :cert_expiration_length_days
+    @ipv4_fallback_enabled       = @hash[:ipv4_fallback_enabled]       if @hash.key? :ipv4_fallback_enabled
 
     @ssl_verify_mode  = @hash[:ssl_verify_mode]  if @hash.key? :ssl_verify_mode
     @ssl_ca_cert      = @hash[:ssl_ca_cert]      if @hash.key? :ssl_ca_cert

lib/rubygems/core_ext/tcpsocket_init.rb

@@ -0,0 +1,49 @@
+require 'socket'
+
+module CoreExtensions
+  module TCPSocketExt
+    def self.prepended(base)
+      base.prepend Initializer
+    end
+
+    module Initializer
+      CONNECTION_TIMEOUT = 5
+      IPV4_DELAY_SECONDS = 0.1
+
+      def initialize(host, serv, *rest)
+        mutex = Mutex.new
+        addrs = []
+        cond_var = ConditionVariable.new
+
+        Addrinfo.foreach(host, serv, nil, :STREAM) do |addr|
+          Thread.report_on_exception = false if defined? Thread.report_on_exception = ()
+
+          Thread.new(addr) do
+            # give head start to ipv6 addresses
+            sleep IPV4_DELAY_SECONDS if addr.ipv4?
+
+            # raises Errno::ECONNREFUSED when ip:port is unreachable
+            Socket.tcp(addr.ip_address, serv, connect_timeout: CONNECTION_TIMEOUT).close
+            mutex.synchronize do
+              addrs << addr.ip_address
+              cond_var.signal
+            end
+          end
+        end
+
+        mutex.synchronize do
+          timeout_time = CONNECTION_TIMEOUT + Time.now.to_f
+          while addrs.empty? && (remaining_time = timeout_time - Time.now.to_f) > 0
+            cond_var.wait(mutex, remaining_time)
+          end
+
+          host = addrs.shift unless addrs.empty?
+        end
+
+        super(host, serv, *rest)
+      end
+    end
+  end
+end
+
+TCPSocket.prepend CoreExtensions::TCPSocketExt

lib/rubygems/remote_fetcher.rb

@@ -78,6 +78,7 @@ def self.fetcher
   #            fetching the gem.
 
   def initialize(proxy=nil, dns=nil, headers={})
+    require 'rubygems/core_ext/tcpsocket_init' if Gem.configuration.ipv4_fallback_enabled
     require 'net/http'
     require 'stringio'
     require 'uri'

test/rubygems/test_gem_config_file.rb

@@ -41,6 +41,7 @@ def test_initialize
     assert_equal true, @cfg.verbose
     assert_equal [@gem_repo], Gem.sources
     assert_equal 365, @cfg.cert_expiration_length_days
+    assert_equal false, @cfg.ipv4_fallback_enabled
 
     File.open @temp_conf, 'w' do |fp|
       fp.puts ":backtrace: true"
@@ -56,6 +57,7 @@ def test_initialize
       fp.puts ":ssl_verify_mode: 0"
       fp.puts ":ssl_ca_cert: /etc/ssl/certs"
       fp.puts ":cert_expiration_length_days: 28"
+      fp.puts ":ipv4_fallback_enabled: true"
     end
 
     util_config_file
@@ -70,6 +72,14 @@ def test_initialize
     assert_equal 0, @cfg.ssl_verify_mode
     assert_equal '/etc/ssl/certs', @cfg.ssl_ca_cert
     assert_equal 28, @cfg.cert_expiration_length_days
+    assert_equal true, @cfg.ipv4_fallback_enabled
+  end
+
+  def test_initialize_ipv4_fallback_enabled_env
+    ENV['IPV4_FALLBACK_ENABLED'] = 'true'
+    util_config_file %W[--config-file #{@temp_conf}]
+
+    assert_equal true, @cfg.ipv4_fallback_enabled
   end
 
   def test_initialize_handle_arguments_config_file

test/rubygems/test_gem_remote_fetcher.rb

@@ -962,6 +962,12 @@ def test_nil_ca_cert
     end
   end
 
+  def test_tcpsocketext_require
+    with_configured_fetcher(":ipv4_fallback_enabled: true") do |fetcher|
+      refute require('rubygems/core_ext/tcpsocket_init')
+    end
+  end
+
   def with_configured_fetcher(config_str = nil, &block)
     if config_str
       temp_conf = File.join @tempdir, '.gemrc'