fix const error responses for Rainbows!

Rainbows! relies on the ERROR_XXX_RESPONSE constants of unicorn
4.x.  Changing the constants in unicorn 4.x will break existing
versions of Rainbows!, so remove the dependency on the constants
and generate the error response dynamically.

Unlike Mongrel, unicorn is unlikely to see malicious traffic and
thus unlikely to benefit from making error messages constant.

For unicorn 5.x, we will drop these constants entirely.

(Rainbows! most likely cannot support check_client_connection
 consistently across all concurrency models since some of them
 pessimistically buffer all writes in userspace.  However, the
 extra concurrency of Rainbows! makes it less likely to be
 overloaded than unicorn, so this feature is likely less useful
 for Rainbows!)

3 files changed, 17 insertions, 12 deletions

diff --git a/lib/unicorn/const.rb b/lib/unicorn/const.rb
index 60a63b1..02e29c7 100644
--- a/lib/unicorn/const.rb
+++ b/lib/unicorn/const.rb
@@ -29,10 +29,12 @@ module Unicorn::Const
 
   # :stopdoc:
   # common errors we'll send back
-  ERROR_400_RESPONSE = "400 Bad Request\r\n\r\n"
-  ERROR_414_RESPONSE = "414 Request-URI Too Long\r\n\r\n"
-  ERROR_413_RESPONSE = "413 Request Entity Too Large\r\n\r\n"
-  ERROR_500_RESPONSE = "500 Internal Server Error\r\n\r\n"
+  # (N.B. these are not used by unicorn, but we won't drop them until
+  #  unicorn 5.x to avoid breaking Rainbows!).
+  ERROR_400_RESPONSE = "HTTP/1.1 400 Bad Request\r\n\r\n"
+  ERROR_414_RESPONSE = "HTTP/1.1 414 Request-URI Too Long\r\n\r\n"
+  ERROR_413_RESPONSE = "HTTP/1.1 413 Request Entity Too Large\r\n\r\n"
+  ERROR_500_RESPONSE = "HTTP/1.1 500 Internal Server Error\r\n\r\n"
 
   EXPECT_100_RESPONSE = "HTTP/1.1 100 Continue\r\n\r\n"
   EXPECT_100_RESPONSE_SUFFIXED = "100 Continue\r\n\r\nHTTP/1.1 "
diff --git a/lib/unicorn/http_response.rb b/lib/unicorn/http_response.rb
index 61563cd..579d957 100644
--- a/lib/unicorn/http_response.rb
+++ b/lib/unicorn/http_response.rb
@@ -17,6 +17,10 @@ module Unicorn::HttpResponse
   }
   CRLF = "\r\n"
 
+  def err_response(code, response_start_sent)
+    "#{response_start_sent ? '' : 'HTTP/1.1 '}#{CODES[code]}\r\n\r\n"
+  end
+
   # writes the rack_response to socket as an HTTP response
   def http_response_write(socket, status, headers, body,
                           response_start_sent=false)
diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
index ef1ea58..aa98aeb 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -519,22 +519,21 @@ class Unicorn::HttpServer
   # if the socket is already closed or broken.  We'll always ensure
   # the socket is closed at the end of this function
   def handle_error(client, e)
-    msg = case e
+    code = case e
     when EOFError,Errno::ECONNRESET,Errno::EPIPE,Errno::EINVAL,Errno::EBADF,
          Errno::ENOTCONN
-      Unicorn::Const::ERROR_500_RESPONSE
+      500
     when Unicorn::RequestURITooLongError
-      Unicorn::Const::ERROR_414_RESPONSE
+      414
     when Unicorn::RequestEntityTooLargeError
-      Unicorn::Const::ERROR_413_RESPONSE
+      413
     when Unicorn::HttpParserError # try to tell the client they're bad
-      Unicorn::Const::ERROR_400_RESPONSE
+      400
     else
       Unicorn.log_error(@logger, "app error", e)
-      Unicorn::Const::ERROR_500_RESPONSE
+      500
     end
-    msg = "HTTP/1.1 #{msg}" unless @request.response_start_sent
-    client.kgio_trywrite(msg)
+    client.kgio_trywrite(err_response(code, @request.response_start_sent))
     client.close
     rescue
   end