Support responses without entity body

Some HTTP verbs imply that no body is sent with
the response. Puma did not respect that.

This led to issues like this one:

    $ curl localhost:9292
    curl: (18) transfer closed with outstanding
    read data remaining

This also breaks persistent connections.

Example program to program to provoke this issue:

    proc do
      [204, {'Conten-Type' => 'text/plain'}, []]
    end

Signed-off-by: Konstantin Haase <konstantin.mailinglists@googlemail.com>

lib/puma/const.rb

@@ -1,3 +1,4 @@
+require 'set'
 
 module Puma
 
@@ -44,6 +45,9 @@ module Puma
     505  => 'HTTP Version not supported'
   }
 
+  # For some HTTP status codes the client only expects headers.
+  STATUS_WITH_NO_ENTITY_BODY = Set.new((100..199).to_a << 204 << 205 << 304)
+
   # Frequently used constants when constructing requests or responses.  Many times
   # the constant just refers to a string with the same contents.  Using these constants
   # gave about a 3% to 10% performance improvement over using the strings directly.

lib/puma/server.rb

@@ -341,6 +341,7 @@ module Puma
         end
 
         content_length = nil
+        no_body = STATUS_WITH_NO_ENTITY_BODY.include? status
 
         if res_body.kind_of? Array and res_body.size == 1
           content_length = res_body[0].size
@@ -395,6 +396,8 @@ module Puma
           when TRANSFER_ENCODING
             allow_chunked = false
             content_length = nil
+          when CONTENT_TYPE
+            next if no_body
           end
 
           vs.split(NEWLINE).each do |v|
@@ -405,6 +408,11 @@ module Puma
           end
         end
 
+        if no_body
+          client.write line_ending
+          return keep_alive
+        end
+
         if include_keepalive_header
           client.write CONNECTION_KEEP_ALIVE
         elsif !keep_alive

test/test_persistent.rb

@@ -10,6 +10,7 @@ class TestPersistent < Test::Unit::TestCase
     @keep_request = "GET / HTTP/1.0\r\nHost: test.com\r\nContent-Type: text/plain\r\nConnection: Keep-Alive\r\n\r\n"
 
     @valid_post = "POST / HTTP/1.1\r\nHost: test.com\r\nContent-Type: text/plain\r\nContent-Length: 5\r\n\r\nhello"
+    @valid_no_body = "GET / HTTP/1.1\r\nHost: test.com\r\nX-Status: 204\r\nContent-Type: text/plain\r\n\r\n"
 
     @headers = { "X-Header" => "Works" }
     @body = ["Hello"]
@@ -17,7 +18,8 @@ class TestPersistent < Test::Unit::TestCase
 
     @simple = lambda do |env|
       @inputs << env['rack.input']
-      [200, @headers, @body]
+      status = Integer(env['HTTP_X_STATUS'] || 200)
+      [status, @headers, @body]
     end
 
     @server = Puma::Server.new @simple
@@ -76,6 +78,17 @@ class TestPersistent < Test::Unit::TestCase
     assert_equal "Hello", @client.read(5)
   end
 
+  def test_no_body_then_get
+    @client << @valid_no_body
+    assert_equal "HTTP/1.1 204 No Content\r\nX-Header: Works\r\n\r\n", lines(3)
+
+    @client << @valid_request
+    sz = @body[0].size.to_s
+
+    assert_equal "HTTP/1.1 200 OK\r\nX-Header: Works\r\nContent-Length: #{sz}\r\n\r\n", lines(4)
+    assert_equal "Hello", @client.read(5)
+  end
+
   def test_chunked
     @body << "Chunked"