allow hash key values more than 255 bytes, it does not actually increase mean
hash element size, because due to aligning a byte after key is not used
anyway in 3/4 cases on 32-bit platforms and in 7/8 cases on 64-bit platforms

src/core/ngx_hash.c

diff --git a/src/core/ngx_hash.c b/src/core/ngx_hash.c
index 2a5b0ad..0c72852 100644
--- a/src/core/ngx_hash.c
+++ b/src/core/ngx_hash.c
@@ -245,7 +245,7 @@
 
 
 #define NGX_HASH_ELT_SIZE(name)                                               \
-    (sizeof(void *) + ngx_align((name)->key.len + 1, sizeof(void *)))
+    (sizeof(void *) + ngx_align((name)->key.len + 2, sizeof(void *)))
 
 ngx_int_t
 ngx_hash_init(ngx_hash_init_t *hinit, ngx_hash_key_t *names, ngx_uint_t nelts)
@@ -257,14 +257,6 @@
     ngx_hash_elt_t  *elt, **buckets;
 
     for (n = 0; n < nelts; n++) {
-        if (names[n].key.len >= 255) {
-            ngx_log_error(NGX_LOG_EMERG, hinit->pool->log, 0,
-                          "the \"%V\" value to hash is to long: %uz bytes, "
-                          "the maximum length can be 255 bytes only",
-                          &names[n].key, names[n].key.len);
-            return NGX_ERROR;
-        }
-
         if (hinit->bucket_size < NGX_HASH_ELT_SIZE(&names[n]) + sizeof(void *))
         {
             ngx_log_error(NGX_LOG_EMERG, hinit->pool->log, 0,
@@ -406,7 +398,7 @@
         elt = (ngx_hash_elt_t *) ((u_char *) buckets[key] + test[key]);
 
         elt->value = names[n].value;
-        elt->len = (u_char) names[n].key.len;
+        elt->len = (u_short) names[n].key.len;
 
         ngx_strlow(elt->name, names[n].key.data, names[n].key.len);
 

src/core/ngx_hash.h

diff --git a/src/core/ngx_hash.h b/src/core/ngx_hash.h
index 76e3c77..beabcb7 100644
--- a/src/core/ngx_hash.h
+++ b/src/core/ngx_hash.h
@@ -14,7 +14,7 @@
 
 typedef struct {
     void             *value;
-    u_char            len;
+    u_short           len;
     u_char            name[1];
 } ngx_hash_elt_t;