From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ganesha.gnumonks.org (ganesha.gnumonks.org [213.95.27.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D6A4C1DA0FB for ; Fri, 13 Sep 2024 12:36:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.27.120 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726231017; cv=none; b=MlE8ZZ4xsMm8D9j6Ilu8VmsP10qNQ9UMJ2TsWShFNNFggQxN1ORDdwpcHn5StrnttnNzOdVPGSs122LUWdjhRBVO9MZZ/rNiSk1yGc36wg+9S08XT2Vk/+/TMKj9Jl/XBQRz/kFLvyv81e3wzF+IeqPfDKA9N8euVDBmvLB4DkU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726231017; c=relaxed/simple; bh=gDOlQ8VXG/P3c5u7ol2krG/r8PCPTk223jW4lvURYU0=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QmeaBNGSq9GzVIM2x4EC4Fiz9a8rbLa0sGfWkMA3gtXl+SC5u0wvaiWXWCDpB3l3qVGfw8Vt/lz+0qdcH3sADavHTJYVapoTccl3/RUTDtCj1a7IsYc8mIQxg8dvmFJoCaCxDSD0HRyLnmKcR0/688ezYI8q6Afh9PZGyjFwBZE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=gnumonks.org; arc=none smtp.client-ip=213.95.27.120 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gnumonks.org Received: from [78.30.37.63] (port=41952 helo=gnumonks.org) by ganesha.gnumonks.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1sp5Xc-00AOOC-MY; Fri, 13 Sep 2024 14:36:50 +0200 Date: Fri, 13 Sep 2024 14:36:47 +0200 From: Pablo Neira Ayuso To: Phil Sutter , Antonio Ojea , Florian Westphal , netfilter-devel@vger.kernel.org Subject: Re: [PATCH nf] netfilter: nft_tproxy: make it terminal Message-ID: References: <20240913102023.3948-1-pablo@netfilter.org> <20240913102347.GA15700@breakpoint.cc> <20240913104101.GA16472@breakpoint.cc> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Spam-Score: -1.9 (-) On Fri, Sep 13, 2024 at 02:00:46PM +0200, Phil Sutter wrote: > Hi, > > On Fri, Sep 13, 2024 at 01:24:25PM +0200, Pablo Neira Ayuso wrote: > > On Fri, Sep 13, 2024 at 01:02:02PM +0200, Antonio Ojea wrote: > > > On Fri, 13 Sept 2024 at 12:47, Pablo Neira Ayuso wrote: > > > > > > > > On Fri, Sep 13, 2024 at 12:41:01PM +0200, Florian Westphal wrote: > > > > > Pablo Neira Ayuso wrote: > > > > > > On Fri, Sep 13, 2024 at 12:23:47PM +0200, Florian Westphal wrote: > > > > > > > Pablo Neira Ayuso wrote: > > > > > > > > tproxy action must be terminal since the intent of the user to steal the > > > > > > > > traffic and redirect to the port. > > > > > > > > Align this behaviour to iptables to make it easier to migrate by issuing > > > > > > > > NF_ACCEPT for packets that are redirect to userspace process socket. > > > > > > > > Otherwise, NF_DROP packet if socket transparent flag is not set on. > > > > > > > > > > > > > > The nonterminal behaviour is intentional. This change will likely > > > > > > > break existing setups. > > > > > > > > > > > > > > nft add rule filter divert tcp dport 80 tproxy to :50080 meta mark set 1 accept > > > > > > > > > > > > > > This is a documented example. > > > > > > > > > > > > Ouch. Example could have been: > > > > > > > > > > > > nft add rule filter divert tcp dport 80 socket transparent meta set 1 tproxy to :50080 > > > > > > > > > > Yes, but its not the same. > > > > > > > > > > With the statements switched, all tcp dport 80 have the mark set. > > > > > With original example, the mark is set only if tproxy found a > > > > > transparent sk. > > > > > > > > Indeed, thanks for correcting me. > > > > > > > > I'm remembering now why this was done to provide to address the ugly > > > > mark hack that xt_TPROXY provides. > > > > > > > > While this is making harder to migrate, making it non-terminal is > > > > allowing to make more handling such as ct/meta marking after it. > > > > > > > > I think we just have to document this in man nft(8). > > > > > > I think that at this point in time the current state can not be broken > > > based on this discussion, I just left the comment in the bugzilla > > > about the possibility but it is clear now that people that have > > > already started using this feature with nftables must not experience a > > > disruption. > > > On the other side, users that need to migrate will have to adapt more > > > things so I don't think it should be a big deal. > > > What I really think is that users should have a way to terminate > > > processing to avoid other rules to interfere with the tproxy > > > functionality > > > > It is possible to add an explicit 'accept' verdict as the example > > above displays: > > > > tcp dport 80 tproxy to :50080 meta mark set 1 accept > > ^^^^^^ > > I wonder if this is sufficient: The packet will still appear in > following chains, etc. So shouldn't one use 'drop' verdict instead or > does that prevent the proxying somehow? > > Hmm. Looking at nft_nat.c, 'accept' seems consistent with what nat > statements do implicitly. Yes, and xt_TPROXY does NF_ACCEPT. On the other hand, I can see it does NF_DROP it socket is not transparent, it does NFT_BREAK instead, so policy keeps evaluating the packet. > > is this sufficient in your opinion? If so, I made this quick update > > for man nft(8). > > Acked-by: Phil Sutter > > In addition to that, I will update tproxy_tg_xlate() in iptables.git to > emit a verdict, too. Thanks, this is very convenient. > Also I should update the respective wiki article[1] once more with added > translation testsuite links - at least the one for TPROXY is missing. Great, thanks. I still have to update wiki to extend set element timeout with the recent information I provided in netfilter@vger.kernel.org ML too.