check duplicate resolver

diff --git a/src/mail/ngx_mail_core_module.c b/src/mail/ngx_mail_core_module.c
index 15627d2453fc11fce68c1085dfef080d402cd182..03635fc4357bf30f4b2908dd63a8c2cb4e2917dc 100644 (file)
--- a/src/mail/ngx_mail_core_module.c
+++ b/src/mail/ngx_mail_core_module.c
@@ -422,6 +422,10 @@ ngx_mail_core_resolver(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 
     value = cf->args->elts;
 
+    if (cscf->resolver != NGX_CONF_UNSET_PTR) {
+        return "is duplicate";
+    }
+
     if (ngx_strcmp(value[1].data, "off") == 0) {
         cscf->resolver = NULL;
         return NGX_CONF_OK;