From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next 1/3] ip: discard IPv4 datagrams with overlapping segments. Date: Thu, 2 Aug 2018 16:33:55 -0700 Message-ID: References: <20180802224600.43070-1-posk@google.com> <20180802224600.43070-2-posk@google.com> <20180802155446.604d1a9b@xeon-e3> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: David Miller , netdev@vger.kernel.org, Eric Dumazet , Florian Westphal To: Stephen Hemminger , Peter Oskolkov Return-path: Received: from mail-pg1-f196.google.com ([209.85.215.196]:45488 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727053AbeHCB1X (ORCPT ); Thu, 2 Aug 2018 21:27:23 -0400 Received: by mail-pg1-f196.google.com with SMTP id f1-v6so1917435pgq.12 for ; Thu, 02 Aug 2018 16:33:58 -0700 (PDT) In-Reply-To: <20180802155446.604d1a9b@xeon-e3> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 08/02/2018 03:54 PM, Stephen Hemminger wrote: > On Thu, 2 Aug 2018 22:45:58 +0000 > Peter Oskolkov wrote: > >> diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h >> index e5ebc83827ab..da1a144f1a51 100644 >> --- a/include/uapi/linux/snmp.h >> +++ b/include/uapi/linux/snmp.h >> @@ -40,6 +40,7 @@ enum >> IPSTATS_MIB_REASMREQDS, /* ReasmReqds */ >> IPSTATS_MIB_REASMOKS, /* ReasmOKs */ >> IPSTATS_MIB_REASMFAILS, /* ReasmFails */ >> + IPSTATS_MIB_REASM_OVERLAPS, /* ReasmOverlaps */ >> IPSTATS_MIB_FRAGOKS, /* FragOKs */ >> IPSTATS_MIB_FRAGFAILS, /* FragFails */ >> IPSTATS_MIB_FRAGCREATES, /* FragCreates */ > > Inserting new entries in the middle of an enum means the numeric > values will change. Isn't this going to break userspace ABI? > I would argue the only exported thing from the kernel are the Key:Val in the /proc files. Not sure why these enum are uapi. Commit 46c2fa39877ed70415ee2b1acfb9129e956f6de4 added LINUX_MIB_TCPFASTOPENBLACKHOLE in the middle, and really nobody complained. Commit 0604475119de5f80dc051a5db055c6a2a75bd542 added LINUX_MIBSTCPMEMORYPRESSURESCHRONO in the middle as well. I am pretty sure we should maintain locality of these counters to lower number of dirtied cache lines, say under IP frag DDOS ;)