From 814eec6950bbf5c1dc153d7a767ddd1c61b41510 Mon Sep 17 00:00:00 2001
From: proller <proller@github.com>
Date: Fri, 7 Sep 2018 02:22:04 +0300
Subject: [PATCH 1/2] NEXT_ON_MULTIPLEX

---
 include/fcgiapp.h | 1 +
 libfcgi/fcgiapp.c | 2 +-
 perl/FCGI.pm      | 8 ++++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/fcgiapp.h b/include/fcgiapp.h
index 07022b1..a901232 100644
--- a/include/fcgiapp.h
+++ b/include/fcgiapp.h
@@ -82,6 +82,7 @@ typedef char **FCGX_ParamArray;
  * restarting upon being interrupted.
  */
 #define FCGI_FAIL_ACCEPT_ON_INTR	1
+#define NEXT_ON_MULTIPLEX	2
 
 /*
  * FCGX_Request -- State associated with a request.
diff --git a/libfcgi/fcgiapp.c b/libfcgi/fcgiapp.c
index 0f7946c..4e1ed52 100644
--- a/libfcgi/fcgiapp.c
+++ b/libfcgi/fcgiapp.c
@@ -1531,7 +1531,7 @@ static int ProcessBeginRecord(int requestId, FCGX_Stream *stream)
     if(requestId == 0 || data->contentLen != sizeof(body)) {
         return FCGX_PROTOCOL_ERROR;
     }
-    if(data->reqDataPtr->isBeginProcessed) {
+    if(data->reqDataPtr->isBeginProcessed && !(data->reqDataPtr->flags & NEXT_ON_MULTIPLEX)) {
         /*
          * The Web server is multiplexing the connection.  This library
          * doesn't know how to handle multiplexing, so respond with
diff --git a/perl/FCGI.pm b/perl/FCGI.pm
index b1ae3c2..39bb00a 100644
--- a/perl/FCGI.pm
+++ b/perl/FCGI.pm
@@ -9,6 +9,7 @@ BEGIN {
 }
 
 sub FAIL_ACCEPT_ON_INTR () { 1 };
+sub NEXT_ON_MULTIPLEX () { 2 };
 
 sub Request(;***$*$) {
     my @defaults = (\*STDIN, \*STDOUT, \*STDERR, \%ENV, 0, FAIL_ACCEPT_ON_INTR);
@@ -140,6 +141,13 @@ It not set, it will just keep on waiting.
 
 =back
 
+=item FCGI::NEXT_ON_MULTIPLEX
+
+If set, do not wait message with current requestId, start processing next request
+It not set, wait finishing current request with correct requestId - this can produce lot of 500 errors with IIS
+
+=back
+
 =back
 
 Example usage:

From 6db1975cb79a854905c2430d1f37749d2d440f2a Mon Sep 17 00:00:00 2001
From: proller <proller@github.com>
Date: Wed, 31 Oct 2018 02:32:51 +0300
Subject: [PATCH 2/2] Also answer error

---
 libfcgi/fcgiapp.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libfcgi/fcgiapp.c b/libfcgi/fcgiapp.c
index 4e1ed52..251055a 100644
--- a/libfcgi/fcgiapp.c
+++ b/libfcgi/fcgiapp.c
@@ -1604,6 +1604,16 @@ static int ProcessHeader(FCGI_Header header, FCGX_Stream *stream)
         return ProcessManagementRecord(header.type, stream);
     }
     if(requestId != data->reqDataPtr->requestId) {
+        if(data->reqDataPtr->flags & NEXT_ON_MULTIPLEX) {
+            FCGI_EndRequestRecord endRequestRecord;
+            endRequestRecord.header = MakeHeader(FCGI_END_REQUEST, requestId, sizeof(endRequestRecord.body), 0);
+            endRequestRecord.body = MakeEndRequestBody(0, FCGI_CANT_MPX_CONN);
+            if(write_it_all(data->reqDataPtr->ipcFd, (char *)&endRequestRecord, sizeof(endRequestRecord)) < 0) {
+                SetError(stream, OS_Errno);
+                return -1;
+            }
+        }
+
         return SKIP;
     }
     if(header.type != data->type) {