From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50314 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751344AbeCLQFb (ORCPT ); Mon, 12 Mar 2018 12:05:31 -0400 Date: Mon, 12 Mar 2018 17:05:28 +0100 From: Sabrina Dubroca To: David Miller Cc: netdev@vger.kernel.org, sbrivio@redhat.com Subject: Re: [PATCH net] ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu Message-ID: <20180312160528.GA30326@bistromath.localdomain> References: <7db505e856b96802375c2e3e822fdc5a3cf66b65.1520613617.git.sd@queasysnail.net> <20180309.160619.741646019216536916.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180309.160619.741646019216536916.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: 2018-03-09, 16:06:19 -0500, David Miller wrote: > From: Sabrina Dubroca > Date: Fri, 9 Mar 2018 17:43:21 +0100 > > > diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h > > index f80524396c06..77d0a78cf7d2 100644 > > --- a/include/net/ip_fib.h > > +++ b/include/net/ip_fib.h > > @@ -59,6 +59,7 @@ struct fib_nh_exception { > > int fnhe_genid; > > __be32 fnhe_daddr; > > u32 fnhe_pmtu; > > + bool fnhe_mtu_locked; > > __be32 fnhe_gw; > > unsigned long fnhe_expires; > > struct rtable __rcu *fnhe_rth_input; > > diff --git a/include/net/route.h b/include/net/route.h > > index 1eb9ce470e25..729bb5e61e9a 100644 > > --- a/include/net/route.h > > +++ b/include/net/route.h > > @@ -64,6 +64,7 @@ struct rtable { > > > > /* Miscellaneous cached information */ > > u32 rt_pmtu; > > + bool rt_mtu_locked; > > > > u32 rt_table_id; > > > > Please use a flag bit for this, we've worked hard to shrink these > datastructures as much as possible. Oops, sorry. > I think if you just choose an unused RTCF_* bit (f.e. 0x02000000) for > the state, you can use that because values propagate into the > rtable->rt_flags, and do not propagate out. So you should be able to > use it in this way privately inside the kernel. What about a bitfield? - u32 rt_pmtu; + u32 rt_mtu_locked:1, + rt_pmtu:31; Since it's going to be private to the kernel, I'd rather not use a value that's in uapi, especially considering that they're almost all used (unless we start recycling). -- Sabrina