From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: Re: [RFC PATCH 0/2] sctp: add new getsockopt option SCTP_SOCKOPT_PEELOFF_KERNEL Date: Wed, 17 Jun 2015 08:38:10 -0300 Message-ID: <55815C22.2000605@gmail.com> References: <20150617102119.GA24677@hmsreliant.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Vlad Yasevich , linux-sctp@vger.kernel.org To: Neil Horman Return-path: Received: from mail-qk0-f182.google.com ([209.85.220.182]:35124 "EHLO mail-qk0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755033AbbFQLiS (ORCPT ); Wed, 17 Jun 2015 07:38:18 -0400 In-Reply-To: <20150617102119.GA24677@hmsreliant.think-freely.org> Sender: netdev-owner@vger.kernel.org List-ID: On 17-06-2015 07:21, Neil Horman wrote: > On Tue, Jun 16, 2015 at 07:42:31PM -0300, Marcelo Ricardo Leitner wrote: >> Hi, >> >> I'm trying to remove a direct dependency of dlm module on sctp one. >> Currently dlm code is calling sctp_do_peeloff() directly and only this >> call is causing the load of sctp module together with dlm. For that, we >> have basically 3 options: >> - Doing a module split on dlm >> - which I'm avoiding because it was already split and was merged (more >> info on patch2 changelog) >> - and the sctp code on it is rather small if compared with sctp module >> itself >> - Using some other infra that gets indirectly activated, like getsockopt() >> - It was like this before, but the exposed sockopt created a file >> descriptor for the new socket and that create some serious issues. >> More info on 2f2d76cc3e93 ("dlm: Do not allocate a fd for peeloff") >> - Doing something like ipv6_stub (which is used by vxlan) or similar >> - but I don't feel that's a good way out here, it doesn't feel right. >> >> So I'm approaching this by going with 2nd option again but this time >> also creating a new sockopt that is only accessible for kernel users of >> this protocol, so that we are safe to directly return a struct socket * >> via getsockopt() results. This is the tricky part of it of this series. >> >> It smells hacky yes but currently most of sctp calls are wrapped behind >> kernel_*(). Even if we set a flag (like netlink does) saying that this >> is a kernel socket, we still have the issue of getting the function call >> through and returning such non-usual return value. >> >> I kept __user marker on sctp_getsockopt_peeloff_kernel() prototype and >> its helpers just to avoid issues with static checkers. >> >> Kernel path not really tested yet.. mainly willing to know what do you >> think, is this feasible? getsockopt option only reachable by kernel >> itself? Couldn't find any other like this. >> >> Thanks, >> Marcelo >> >> Marcelo Ricardo Leitner (2): >> sctp: add new getsockopt option SCTP_SOCKOPT_PEELOFF_KERNEL >> dlm: avoid using sctp_do_peeloff directly >> >> fs/dlm/lowcomms.c | 17 ++++++++--------- >> include/uapi/linux/sctp.h | 12 ++++++++++++ >> net/sctp/socket.c | 39 +++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 59 insertions(+), 9 deletions(-) >> >> -- >> 2.4.1 >> >> > > Why not just use the existing PEELOFF socket option with the kernel_getsockopt > interface, and sockfd_lookup to translate the returned value back to a socket > struct? That seems less redundant and less hack-ish to me. It was like that before commit 2f2d76cc3e93 ("dlm: Do not allocate a fd for peeloff"), but it caused serious issues due to the fd allocation, so that's what I'm willing to avoid now. References: http://article.gmane.org/gmane.linux.network.drbd/22529 https://bugzilla.redhat.com/show_bug.cgi?id=1075629 (this one is closed, sorry) Marcelo