Omit port in Host header for default ports

Setting default port in Host header break some web servers
like "Apache Coyote".

Most clients don't set this default port too:
* request/request#515 (comment)
* https://github.com/ruby/ruby/blob/d46336e71731aa64d71d4573b2741b7de43ec340/lib/net/http/generic_request.rb#L18

lib/rack/reverse_proxy.rb

@@ -46,7 +46,11 @@ def proxy(env, source_request, matcher)
       target_request_headers = extract_http_request_headers(source_request.env)
 
       if options[:preserve_host]
-        target_request_headers['HOST'] = "#{uri.host}:#{uri.port}"
+        if uri.port == uri.default_port
+          target_request_headers['HOST'] = uri.host
+        else
+          target_request_headers['HOST'] = "#{uri.host}:#{uri.port}"
+        end
       end
 
       if options[:x_forwarded_host]

spec/rack/reverse_proxy_spec.rb

@@ -37,10 +37,10 @@ def app
       last_response.body.should == "Proxied App2"
     end
 
-    it "should set the Host header" do
+    it "should set the Host header w/o default port" do
       stub_request(:any, 'example.com/test/stuff')
       get '/test/stuff'
-      a_request(:get, 'http://example.com/test/stuff').with(:headers => {"Host" => "example.com:80"}).should have_been_made
+      a_request(:get, 'http://example.com/test/stuff').with(:headers => {"Host" => "example.com"}).should have_been_made
     end
 
     it "should set the X-Forwarded-Host header to the proxying host by default" do
@@ -49,6 +49,20 @@ def app
       a_request(:get, 'http://example.com/test/stuff').with(:headers => {'X-Forwarded-Host' => 'example.org'}).should have_been_made
     end
 
+    describe "with non-default port" do
+      def app
+        Rack::ReverseProxy.new(dummy_app) do
+          reverse_proxy '/test', 'http://example.com:8080/'
+        end
+      end
+
+      it "should set the Host header including non-default port" do
+        stub_request(:any, 'example.com:8080/test/stuff')
+        get '/test/stuff'
+        a_request(:get, 'http://example.com:8080/test/stuff').with(:headers => {"Host" => "example.com:8080"}).should have_been_made
+      end
+    end
+
     describe "with preserve host turned off" do
       def app
         Rack::ReverseProxy.new(dummy_app) do
@@ -166,6 +180,25 @@ def app
         last_response.body.should == "Proxied Secure App"
       end
 
+      it "should set the Host header w/o default port" do
+        stub_request(:any, 'https://example.com/test/stuff')
+        get '/test/stuff'
+        a_request(:get, 'https://example.com/test/stuff').with(:headers => {"Host" => "example.com"}).should have_been_made
+      end
+    end
+
+    describe "with a https route on non-default port" do
+      def app
+        Rack::ReverseProxy.new(dummy_app) do
+          reverse_proxy '/test', 'https://example.com:8443'
+        end
+      end
+
+      it "should set the Host header including non-default port" do
+        stub_request(:any, 'https://example.com:8443/test/stuff')
+        get '/test/stuff'
+        a_request(:get, 'https://example.com:8443/test/stuff').with(:headers => {"Host" => "example.com:8443"}).should have_been_made
+      end
     end
 
     describe "with a route as a string" do