bugfix: when variable is cacheable and indexed, setting the request "Host" header should clear any existing cached $host variable value so that subsequent reads return the expected result.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: dndx

src/ngx_http_lua_common.h

@@ -227,6 +227,8 @@ struct ngx_http_lua_main_conf_s {
     ngx_int_t            busy_buf_ptr_count;
 #endif
 
+    ngx_int_t            host_var_index;
+
     unsigned             requires_header_filter:1;
     unsigned             requires_body_filter:1;
     unsigned             requires_capture_filter:1;

src/ngx_http_lua_headers_in.c

@@ -432,10 +432,14 @@ static ngx_int_t
 ngx_http_set_host_header(ngx_http_request_t *r, ngx_http_lua_header_val_t *hv,
     ngx_str_t *value)
 {
-    ngx_str_t host;
+    ngx_str_t                    host;
+    ngx_http_lua_main_conf_t    *lmcf;
+    ngx_http_variable_value_t   *var;
 
     dd("server new value len: %d", (int) value->len);
 
+    lmcf = ngx_http_get_module_main_conf(r, ngx_http_lua_module);
+
     if (value->len) {
         host= *value;
 
@@ -449,6 +453,10 @@ ngx_http_set_host_header(ngx_http_request_t *r, ngx_http_lua_header_val_t *hv,
         r->headers_in.server = *value;
     }
 
+    var = &r->variables[lmcf->host_var_index];
+    var->valid = 0;
+    var->not_found = 0;
+
     return ngx_http_set_builtin_header(r, hv, value);
 }
 

src/ngx_http_lua_module.c

@@ -638,9 +638,15 @@ ngx_http_lua_init(ngx_conf_t *cf)
 #if !defined(NGX_LUA_NO_FFI_API) || nginx_version >= 1011011
     ngx_pool_cleanup_t         *cln;
 #endif
+    ngx_str_t                   name = ngx_string("host");
 
     lmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_lua_module);
 
+    lmcf->host_var_index = ngx_http_get_variable_index(cf, &name);
+    if (lmcf->host_var_index == NGX_ERROR) {
+        return NGX_ERROR;
+    }
+
     if (ngx_http_lua_prev_cycle != ngx_cycle) {
         ngx_http_lua_prev_cycle = ngx_cycle;
         multi_http_blocks = 0;

t/028-req-header.t

@@ -8,7 +8,7 @@ use Test::Nginx::Socket::Lua;
 
 repeat_each(2);
 
-plan tests => repeat_each() * (2 * blocks() + 43);
+plan tests => repeat_each() * (2 * blocks() + 44);
 
 #no_diff();
 no_long_string();
@@ -2008,3 +2008,25 @@ found 3 headers.
 --- no_error_log
 lua exceeding request header limit
 [error]
+
+
+
+=== TEST 61: setting Host header clears cached $host variable
+--- config
+    location /req-header {
+        # this makes $host indexed and cacheable
+        set $foo $host;
+
+        content_by_lua_block {
+            ngx.say(ngx.var.host)
+            ngx.req.set_header("Host", "new");
+            ngx.say(ngx.var.host)
+        }
+    }
+--- request
+GET /req-header
+--- response_body
+localhost
+new
+--- no_error_log
+[error]