From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B191FC33CB1 for ; Tue, 14 Jan 2020 10:25:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DB2A207FF for ; Tue, 14 Jan 2020 10:25:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729191AbgANKZT (ORCPT ); Tue, 14 Jan 2020 05:25:19 -0500 Received: from orbyte.nwl.cc ([151.80.46.58]:44948 "EHLO orbyte.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726156AbgANKZT (ORCPT ); Tue, 14 Jan 2020 05:25:19 -0500 Received: from n0-1 by orbyte.nwl.cc with local (Exim 4.91) (envelope-from ) id 1irJNs-0005RO-Hn; Tue, 14 Jan 2020 11:25:16 +0100 Date: Tue, 14 Jan 2020 11:25:16 +0100 From: Phil Sutter To: Pablo Neira Ayuso Cc: netfilter-devel@vger.kernel.org, Florian Westphal Subject: Re: [PATCH nft 1/3] libnftables: add nft_ctx_set_netns() Message-ID: <20200114102516.GD20229@orbyte.nwl.cc> Mail-Followup-To: Phil Sutter , Pablo Neira Ayuso , netfilter-devel@vger.kernel.org, Florian Westphal References: <20200109172115.229723-1-pablo@netfilter.org> <20200109172115.229723-2-pablo@netfilter.org> <20200110125311.GP20229@orbyte.nwl.cc> <20200112102802.7bvwieqaza3zdbza@salvia> <20200112104027.ijjcv34glvnkhnvc@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200112104027.ijjcv34glvnkhnvc@salvia> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Hi Pablo, On Sun, Jan 12, 2020 at 11:40:27AM +0100, Pablo Neira Ayuso wrote: > On Sun, Jan 12, 2020 at 11:28:02AM +0100, Pablo Neira Ayuso wrote: > > On Fri, Jan 10, 2020 at 01:53:11PM +0100, Phil Sutter wrote: > > > On Thu, Jan 09, 2020 at 06:21:13PM +0100, Pablo Neira Ayuso wrote: > > > [...] > > > > diff --git a/include/nftables/libnftables.h b/include/nftables/libnftables.h > > > > index 765b20dd71ee..887628959ac6 100644 > > > > --- a/include/nftables/libnftables.h > > > > +++ b/include/nftables/libnftables.h > > > > @@ -34,10 +34,13 @@ enum nft_debug_level { > > > > * Possible flags to pass to nft_ctx_new() > > > > */ > > > > #define NFT_CTX_DEFAULT 0 > > > > +#define NFT_CTX_NETNS 1 > > > > > > What is this needed for? > > > > The socket is initialized from nft_ctx_init(), and such initialization > > needs to happen after the netns switch. > > s/nft_ctx_init()/nft_ctx_new() Ah, I missed that socket init in nft_ctx_new() happens only if flags is zero. > > > > struct nft_ctx *nft_ctx_new(uint32_t flags); > > > > void nft_ctx_free(struct nft_ctx *ctx); > > > > > > > > +int nft_ctx_set_netns(struct nft_ctx *ctx, const char *netns); > > > > > > Is there a way to select init ns again? > > > > AFAIK, setns() does not let you go back to init ns once set. I noticed something I find worse, namely that libnftables as a library changes the application's netns. Anything it does after changing the context's netns applies to that netns only, no matter if it's creating a new nft context with NFT_CtX_DEFAULT flag or call iproute via system(). If we can't find a way to exit the netns again, one can safely assume that we are trapping a user's application in a netns with this feature. Maybe we should restrict per-netns operation to nft utility and perform the netns switch there? Maybe we could provide a "switch_netns()" routine in libnftables which is not bound to nft context so users may use it in their application? Cheers, Phil