Add :inet4 transport option to disable IPv4 fallback (#425)

lib/mint/core/transport/ssl.ex

@@ -323,6 +323,7 @@ defmodule Mint.Core.Transport.SSL do
 
   defp connect(address, hostname, port, opts) do
     timeout = Keyword.get(opts, :timeout, @default_timeout)
+    inet4? = Keyword.get(opts, :inet4, true)
     inet6? = Keyword.get(opts, :inet6, false)
 
     opts = ssl_opts(String.to_charlist(hostname), opts)
@@ -334,8 +335,11 @@ defmodule Mint.Core.Transport.SSL do
         {:ok, sslsocket} ->
           {:ok, sslsocket}
 
-        _error ->
+        _error when inet4? ->
           wrap_err(:ssl.connect(address, port, opts, timeout))
+
+        error ->
+          wrap_err(error)
       end
     else
       # Use the defaults provided by ssl/gen_tcp.
@@ -428,7 +432,7 @@ defmodule Mint.Core.Transport.SSL do
     default_ssl_opts(hostname)
     |> Keyword.merge(opts)
     |> Keyword.merge(@transport_opts)
-    |> Keyword.drop([:timeout, :inet6])
+    |> Keyword.drop([:timeout, :inet4, :inet6])
     |> add_verify_opts(hostname)
     |> remove_incompatible_ssl_opts()
     |> add_ciphers_opt()

lib/mint/core/transport/tcp.ex

@@ -19,12 +19,13 @@ defmodule Mint.Core.Transport.TCP do
     opts = Keyword.delete(opts, :hostname)
 
     timeout = Keyword.get(opts, :timeout, @default_timeout)
+    inet4? = Keyword.get(opts, :inet4, true)
     inet6? = Keyword.get(opts, :inet6, false)
 
     opts =
       opts
       |> Keyword.merge(@transport_opts)
-      |> Keyword.drop([:alpn_advertised_protocols, :timeout, :inet6])
+      |> Keyword.drop([:alpn_advertised_protocols, :timeout, :inet4, :inet6])
 
     if inet6? do
       # Try inet6 first, then fall back to the defaults provided by
@@ -33,8 +34,11 @@ defmodule Mint.Core.Transport.TCP do
         {:ok, socket} ->
           {:ok, socket}
 
-        _error ->
+        _error when inet4? ->
           wrap_err(:gen_tcp.connect(address, port, opts, timeout))
+
+        error ->
+          wrap_err(error)
       end
     else
       # Use the defaults provided by gen_tcp.

lib/mint/http.ex

@@ -299,6 +299,12 @@ defmodule Mint.HTTP do
       seconds), and may be overridden by the caller. Set to `:infinity` to
       disable the connect timeout.
 
+    * `:inet6` - if set to `true` enables IPv6 connection. Defaults to `false`
+      and may be overridden by the caller.
+
+    * `:inet4` - if set to `true` falls back to IPv4 if IPv6 connection fails.
+      Defaults to `true` and may be overridden by the caller.
+
   Options for `:https` only:
 
     * `:alpn_advertised_protocols` - managed by Mint. Cannot be overridden.

test/mint/core/transport/ssl_test.exs

@@ -186,15 +186,15 @@ defmodule Mint.Core.Transport.SSLTest do
 
       task =
         Task.async(fn ->
-          with {:ok, socket} <- :ssl.transport_accept(listen_socket) do
-            if function_exported?(:ssl, :handshake, 1) do
-              {:ok, _} = apply(:ssl, :handshake, [socket])
-            else
-              :ok = apply(:ssl, :ssl_accept, [socket])
-            end
-
-            {:ok, socket}
+          {:ok, socket} = :ssl.transport_accept(listen_socket)
+
+          if function_exported?(:ssl, :handshake, 1) do
+            {:ok, _} = apply(:ssl, :handshake, [socket])
+          else
+            :ok = apply(:ssl, :ssl_accept, [socket])
           end
+
+          {:ok, socket}
         end)
 
       assert {:ok, _socket} =
@@ -208,6 +208,73 @@ defmodule Mint.Core.Transport.SSLTest do
 
       assert {:ok, _server_socket} = Task.await(task)
     end
+
+    test "can fall back to IPv4 if IPv6 fails" do
+      ssl_opts = [
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true,
+        certfile: Path.expand("../../../support/mint/certificate.pem", __DIR__),
+        keyfile: Path.expand("../../../support/mint/key.pem", __DIR__)
+      ]
+
+      {:ok, listen_socket} = :ssl.listen(0, ssl_opts)
+      {:ok, {_address, port}} = :ssl.sockname(listen_socket)
+
+      task =
+        Task.async(fn ->
+          {:ok, socket} = :ssl.transport_accept(listen_socket)
+
+          if function_exported?(:ssl, :handshake, 1) do
+            {:ok, _} = apply(:ssl, :handshake, [socket])
+          else
+            :ok = apply(:ssl, :ssl_accept, [socket])
+          end
+
+          {:ok, socket}
+        end)
+
+      assert {:ok, _socket} =
+               SSL.connect("localhost", port,
+                 active: false,
+                 inet6: true,
+                 timeout: 1000,
+                 verify: :verify_none
+               )
+
+      assert {:ok, _server_socket} = Task.await(task)
+    end
+
+    test "does not fall back to IPv4 if IPv4 is disabled" do
+      ssl_opts = [
+        :inet,
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true,
+        certfile: Path.expand("../../../support/mint/certificate.pem", __DIR__),
+        keyfile: Path.expand("../../../support/mint/key.pem", __DIR__)
+      ]
+
+      {:ok, listen_socket} = :ssl.listen(0, ssl_opts)
+      {:ok, {_address, port}} = :ssl.sockname(listen_socket)
+
+      Task.async(fn ->
+        {:ok, _socket} = :ssl.transport_accept(listen_socket)
+      end)
+
+      assert {:error, %Mint.TransportError{reason: :econnrefused}} =
+               SSL.connect("localhost", port,
+                 active: false,
+                 inet6: true,
+                 inet4: false,
+                 timeout: 1000,
+                 verify: :verify_none
+               )
+    end
   end
 
   describe "controlling_process/2" do

test/mint/core/transport/tcp_test.exs

@@ -0,0 +1,208 @@
+defmodule Mint.Core.Transport.TCPTest do
+  use ExUnit.Case, async: true
+
+  alias Mint.Core.Transport.TCP
+
+  describe "connect/3" do
+    test "can connect to IPv6 addresses" do
+      tcp_opts = [
+        :inet6,
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true
+      ]
+
+      {:ok, listen_socket} = :gen_tcp.listen(0, tcp_opts)
+      {:ok, {_address, port}} = :inet.sockname(listen_socket)
+
+      task =
+        Task.async(fn ->
+          {:ok, _socket} = :gen_tcp.accept(listen_socket)
+        end)
+
+      assert {:ok, _socket} =
+               TCP.connect({127, 0, 0, 1}, port,
+                 active: false,
+                 inet6: true,
+                 timeout: 1000
+               )
+
+      assert {:ok, _server_socket} = Task.await(task)
+    end
+
+    test "can fall back to IPv4 if IPv6 fails" do
+      tcp_opts = [
+        :inet6,
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true
+      ]
+
+      {:ok, listen_socket} = :gen_tcp.listen(0, tcp_opts)
+      {:ok, {_address, port}} = :inet.sockname(listen_socket)
+
+      task =
+        Task.async(fn ->
+          {:ok, _socket} = :gen_tcp.accept(listen_socket)
+        end)
+
+      assert {:ok, _socket} =
+               TCP.connect("localhost", port,
+                 active: false,
+                 inet6: true,
+                 timeout: 1000
+               )
+
+      assert {:ok, _server_socket} = Task.await(task)
+    end
+
+    test "does not fall back to IPv4 if IPv4 is disabled" do
+      tcp_opts = [
+        :inet,
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true
+      ]
+
+      {:ok, listen_socket} = :gen_tcp.listen(0, tcp_opts)
+      {:ok, {_address, port}} = :inet.sockname(listen_socket)
+
+      Task.async(fn ->
+        {:ok, _socket} = :gen_tcp.accept(listen_socket)
+      end)
+
+      assert {:error, %Mint.TransportError{reason: :econnrefused}} =
+               TCP.connect("localhost", port,
+                 active: false,
+                 inet6: true,
+                 inet4: false,
+                 timeout: 1000
+               )
+    end
+  end
+
+  describe "controlling_process/2" do
+    @describetag :capture_log
+
+    setup do
+      parent = self()
+      ref = make_ref()
+
+      ssl_opts = [
+        mode: :binary,
+        packet: :raw,
+        active: false,
+        reuseaddr: true,
+        nodelay: true
+      ]
+
+      spawn_link(fn ->
+        {:ok, listen_socket} = :gen_tcp.listen(0, ssl_opts)
+        {:ok, {_address, port}} = :inet.sockname(listen_socket)
+        send(parent, {ref, port})
+
+        {:ok, socket} = :gen_tcp.accept(listen_socket)
+
+        send(parent, {ref, socket})
+
+        # Keep the server alive forever.
+        :ok = Process.sleep(:infinity)
+      end)
+
+      assert_receive {^ref, port} when is_integer(port), 500
+
+      {:ok, socket} = TCP.connect("localhost", port, [])
+      assert_receive {^ref, server_socket}, 200
+
+      {:ok, server_port: port, socket: socket, server_socket: server_socket}
+    end
+
+    test "changing the controlling process of a active: :once socket",
+         %{socket: socket, server_socket: server_socket} do
+      parent = self()
+      ref = make_ref()
+
+      # Send two SSL messages (that get translated to Erlang messages right
+      # away because of "nodelay: true"), but wait after each one so that
+      # it actually arrives and we can set the socket back to active: :once.
+      :ok = TCP.setopts(socket, active: :once)
+      :ok = :gen_tcp.send(server_socket, "some data 1")
+      Process.sleep(100)
+
+      :ok = TCP.setopts(socket, active: :once)
+      :ok = :gen_tcp.send(server_socket, "some data 2")
+
+      wait_until_passes(500, fn ->
+        {:messages, messages} = Process.info(self(), :messages)
+        assert {:tcp, socket, "some data 1"} in messages
+        assert {:tcp, socket, "some data 2"} in messages
+      end)
+
+      other_process = spawn_link(fn -> process_mirror(parent, ref) end)
+
+      assert :ok = TCP.controlling_process(socket, other_process)
+
+      assert_receive {^ref, {:tcp, ^socket, "some data 1"}}
+      assert_receive {^ref, {:tcp, ^socket, "some data 2"}}
+
+      refute_received _message
+    end
+
+    test "changing the controlling process of a passive socket",
+         %{socket: socket, server_socket: server_socket} do
+      parent = self()
+      ref = make_ref()
+
+      :ok = :gen_tcp.send(server_socket, "some data")
+
+      other_process =
+        spawn_link(fn ->
+          assert_receive message, 500
+          send(parent, {ref, message})
+        end)
+
+      assert :ok = TCP.controlling_process(socket, other_process)
+      assert {:ok, [active: false]} = TCP.getopts(socket, [:active])
+      :ok = TCP.setopts(socket, active: :once)
+
+      assert_receive {^ref, {:tcp, ^socket, "some data"}}, 500
+
+      refute_received _message
+    end
+
+    test "changing the controlling process of a closed socket",
+         %{socket: socket} do
+      other_process = spawn_link(fn -> :ok = Process.sleep(:infinity) end)
+
+      :ok = TCP.close(socket)
+
+      assert {:error, _error} = TCP.controlling_process(socket, other_process)
+    end
+  end
+
+  defp process_mirror(parent, ref) do
+    receive do
+      message ->
+        send(parent, {ref, message})
+        process_mirror(parent, ref)
+    end
+  end
+
+  defp wait_until_passes(time_left, fun) when time_left <= 0 do
+    fun.()
+  end
+
+  defp wait_until_passes(time_left, fun) do
+    fun.()
+  rescue
+    _exception ->
+      Process.sleep(10)
+      wait_until_passes(time_left - 10, fun)
+  end
+end