From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: Re: [PATCH nf-next] netfilter: nf_defrag_ipv4: Add sysctl to disable per interface Date: Tue, 7 Nov 2017 11:30:13 +0100 Message-ID: <20171107103013.GA5512@breakpoint.cc> References: <1509762520-17873-1-git-send-email-subashab@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netfilter-devel@vger.kernel.org, steffen.klassert@secunet.com, pablo@netfilter.org To: Subash Abhinov Kasiviswanathan Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:50042 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750917AbdKGKat (ORCPT ); Tue, 7 Nov 2017 05:30:49 -0500 Content-Disposition: inline In-Reply-To: <1509762520-17873-1-git-send-email-subashab@codeaurora.org> Sender: netfilter-devel-owner@vger.kernel.org List-ID: Subash Abhinov Kasiviswanathan wrote: > Add a sysctl nf_ipv4_defrag_skip to skip defragmentation per > interface. This is set 0 to preserve existing behavior (always > defrag per interface). > > This is useful for pure ipv4 forwarding scenarios (without NAT) > in conjunction with xfrm. It appears that network stack defrags > the packets and then forwards them to xfrm which then encrypts > and then later fragments them on a different boundary compared > to the source. This breaks connection tracking for packets coming in via such interfaces. Nowadays we only enable defrag in a network namespace if the ip/nftables ruleset requires it, so this setting would be counter-productive. > An example of this usage is for fixing wifi calling on networks > where certain routers are configured to drop fragments explicitly. Yay... does that happen for all frags or is this related to df bit somehow?