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/core/ngx_hash.h
+++ b/src/core/ngx_hash.h
@@ -89,12 +89,15 @@ typedef struct {
 } ngx_hash_keys_arrays_t;
 
 
-typedef struct {
+typedef struct ngx_table_elt_s  ngx_table_elt_t;
+
+struct ngx_table_elt_s {
     ngx_uint_t        hash;
     ngx_str_t         key;
     ngx_str_t         value;
     u_char           *lowcase_key;
-} ngx_table_elt_t;
+    ngx_table_elt_t  *next;
+};
 
 
 void *ngx_hash_find(ngx_hash_t *hash, ngx_uint_t key, u_char *name, size_t len);