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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06FA2CDB46E for ; Thu, 12 Oct 2023 19:48:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1442712AbjJLTsV (ORCPT ); Thu, 12 Oct 2023 15:48:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1442633AbjJLTsP (ORCPT ); Thu, 12 Oct 2023 15:48:15 -0400 Received: from ganesha.gnumonks.org (ganesha.gnumonks.org [IPv6:2001:780:45:1d:225:90ff:fe52:c662]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82413D8 for ; Thu, 12 Oct 2023 12:47:42 -0700 (PDT) Received: from [78.30.34.192] (port=35870 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 1qr1ee-004NUm-Ls; Thu, 12 Oct 2023 21:47:38 +0200 Date: Thu, 12 Oct 2023 21:47:31 +0200 From: Pablo Neira Ayuso To: Phil Sutter Cc: netfilter-devel@vger.kernel.org Subject: Re: [iptables PATCH] extensions: string: Clarify description of --to Message-ID: References: <20231012160842.18584-1-phil@nwl.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231012160842.18584-1-phil@nwl.cc> Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > String match indeed returns a match as long as the given pattern starts > in the range of --from and --to, update the text accordingly. > Also add a note regarding fragment boundaries. > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > Signed-off-by: Phil Sutter > --- > extensions/libxt_string.man | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man > index 2a470ece19c9d..efdda492ae78d 100644 > --- a/extensions/libxt_string.man > +++ b/extensions/libxt_string.man > @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri > Set the offset from which it starts looking for any matching. If not passed, default is 0. > .TP > \fB\-\-to\fP \fIoffset\fP > -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 > -(counting from 0) is the last one that is scanned. > +Set the offset up to which should be scanned. If the pattern does not start > +within this offset, it is not considered a match. > If not passed, default is the packet size. > +A second function of this parameter is instructing the kernel how much data > +from the packet should be provided. With non-linear skbuffs (e.g. due to > +fragmentation), a pattern extending past this offset may not be found. Also see > +the related note below about Boyer-Moore algorithm in these cases. Then, matching on: - linear skbuff: if the pattern falls within from-to, all good. - non-linear skbuff: if pattern falls within from-to, but remaining patter This is clearly broken, the fix is just to document this? No attempt to fix it this from the kernel?