--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -1809,6 +1809,35 @@ ngx_http_set_exten(ngx_http_request_t *r
 
 
 ngx_int_t
+ngx_http_set_etag(ngx_http_request_t *r)
+{
+    ngx_table_elt_t  *etag;
+
+    etag = ngx_list_push(&r->headers_out.headers);
+    if (etag == NULL) {
+        return NGX_ERROR;
+    }
+
+    etag->hash = 1;
+    ngx_str_set(&etag->key, "ETag");
+
+    etag->value.data = ngx_pnalloc(r->pool, NGX_OFF_T_LEN + NGX_TIME_T_LEN + 3);
+    if (etag->value.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    etag->value.len = ngx_sprintf(etag->value.data, "\"%xT-%xO\"",
+                                  r->headers_out.last_modified_time,
+                                  r->headers_out.content_length_n)
+                      - etag->value.data;
+
+    r->headers_out.etag = etag;
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
 ngx_http_send_response(ngx_http_request_t *r, ngx_uint_t status,
     ngx_str_t *ct, ngx_http_complex_value_t *cv)
 {