FastCGI: combining headers with identical names (ticket #1724). FastCGI responder is expected to receive CGI/1.1 environment variables in the parameters (see section "6.2 Responder" of the FastCGI specification). Obviously enough, there cannot be multiple environment variables with the same name. Further, CGI specification (RFC 3875, section "4.1.18. Protocol-Specific Meta-Variables") explicitly requires to combine headers: "If multiple header fields with the same field-name are received then the server MUST rewrite them as a single value having the same semantics".

--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -242,6 +242,8 @@ typedef struct {
 
     unsigned                          connection_type:2;
     unsigned                          chunked:1;
+    unsigned                          multi:1;
+    unsigned                          multi_linked:1;
     unsigned                          msie:1;
     unsigned                          msie6:1;
     unsigned                          opera:1;