Here's a fix for a typo;
ngx_http_rdns_module.c
-l709
static void dns_handler(ngx_resolver_ctx_t * rctx) {;
+l709
static void dns_handler(ngx_resolver_ctx_t * rctx) {
Posted at Nginx Forum: http://forum.nginx.org/read.php?2,243191,243213#msg-243213