From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Sutter Subject: netstat and dual stack sockets Date: Mon, 15 Jun 2015 22:54:21 +0200 Message-ID: <20150615205421.GA22616@orbit.nwl.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from orbit.nwl.cc ([176.31.251.142]:59900 "EHLO mail.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751941AbbFOVAL (ORCPT ); Mon, 15 Jun 2015 17:00:11 -0400 Received: from mail.nwl.cc (orbit [127.0.0.1]) by mail.nwl.cc (Postfix) with ESMTP id 4036920094 for ; Mon, 15 Jun 2015 22:54:22 +0200 (CEST) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hi, A socket listening on any AF_INET6 address will receive IPv4 traffic as well, as long as it does not set IPV6_V6ONLY (or sysctl net.ipv6.bindv6only is set). Apache APR e.g. explicitly disables IPV6_V6ONLY for listening sockets. As I see it, a user has no way of detecting the listening socket in this address family: it does not show in /proc/net/{tcp,udp} nor do 'netstat', 'ss' or 'lsof' print any additional information about those sockets over pure IPv6 ones. Is this correct? If so, are there any intentions to export the missing information to userspace? Phil