From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sabrina Dubroca Subject: Re: [net-next 1/2] dummy: add device MTU validation check Date: Fri, 22 Sep 2017 14:23:15 +0200 Message-ID: <20170922122315.GA3446@bistromath.localdomain> References: <1506000722-40095-1-git-send-email-zhangshengju@cmss.chinamobile.com> <1506000722-40095-2-git-send-email-zhangshengju@cmss.chinamobile.com> <1506006138.29839.132.camel@edumazet-glaptop3.roam.corp.google.com> <20170922085610.GA4544@bistromath.localdomain> <1506078309.29839.161.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Jarod Wilson , Zhang Shengju , davem@davemloft.net, willemb@google.com, stephen@networkplumber.org, netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32640 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039AbdIVMXW (ORCPT ); Fri, 22 Sep 2017 08:23:22 -0400 Content-Disposition: inline In-Reply-To: <1506078309.29839.161.camel@edumazet-glaptop3.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: 2017-09-22, 04:05:09 -0700, Eric Dumazet wrote: > On Fri, 2017-09-22 at 10:56 +0200, Sabrina Dubroca wrote: > > 2017-09-21, 08:02:18 -0700, Eric Dumazet wrote: > > > On Thu, 2017-09-21 at 21:32 +0800, Zhang Shengju wrote: > > > > Currently, any mtu value can be assigned when adding a new dummy device: > > > > [~]# ip link add name dummy1 mtu 100000 type dummy > > > > [~]# ip link show dummy1 > > > > 15: dummy1: mtu 100000 qdisc noop state DOWN mode DEFAULT group default qlen 1000 > > > > link/ether 0a:61:6b:16:14:ce brd ff:ff:ff:ff:ff:ff > > > > > > > > This patch adds device MTU validation check. > > > > > > What is wrong with big MTU on dummy ? > > > > It looks like the "centralize MTU checking" series broke that, but > > only for changing the MTU on an existing dummy device. Commit > > a52ad514fdf3 defined min_mtu/max_mtu in ether_setup, which dummy uses, > > but there was no MTU check in dummy prior to that commit. > > > > It looks like we accept big mtu on loopback, right ? Yes. I only meant that before commit a52ad514fdf3, there was no range check on dummy's MTU. Commit 25e3e84b183a ("dummy: expend mtu range for dummy device") and 8b1efc0f83f1 ("net: remove MTU limits on a few ether_setup callers") fixed that only partially. It's the same with ifb, btw, it didn't have any check before a52ad514fdf3, so we should set min_mtu = max_mtu = 0. -- Sabrina