Date: Tue, 17 Mar 2009 23:35:11 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Paolo Pisati <p.pisati@oltrelinux.com> Cc: freebsd-ipfw@FreeBSD.org, Dmitriy Demidov <dima_bsd@inbox.lv>, Alex Dupre <ale@FreeBSD.org> Subject: Re: keep-state rules inadequately handles big UDP packets or fragmented IP packets? Message-ID: <20090317223511.GB95451@onelab2.iet.unipi.it> In-Reply-To: <49C01E08.9050709@oltrelinux.com> References: <200903132246.49159.dima_bsd@inbox.lv> <20090313214327.GA1675@onelab2.iet.unipi.it> <49BF61E7.7020305@FreeBSD.org> <49BFB9B2.9090909@oltrelinux.com> <20090317190123.GB89417@onelab2.iet.unipi.it> <49C01E08.9050709@oltrelinux.com>
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On Tue, Mar 17, 2009 at 11:02:48PM +0100, Paolo Pisati wrote: > Luigi Rizzo wrote: > > > >Thinking more about it, i believe that calling reass as an explicit > >firewall action is useless, because if ip_reass fails due to lack of > >all fragments you are back to square one: > > what do I do with this fragment ? > > > > AFAIK ip_reass() never fails: if it's the last fragment it reassembles > the packet and return it, else it queues the fragment for later > reassembly. Ok then we may have a plan: you could do is implement REASS as an action (not as a microinstruction), with the following behaviour: - if the packet is a complete one, the rule behaves as a "count" (i.e. the firewall continues with the next rule); - if the packet is a fragment and can be reassembled, the rule behaves as a "count" and the mbuf is replaced with the full packet; - if the packet is a fragment and cannot be reassembled, the rule behaves as a "drop" (i.e. processing stops) and the packet is swallowed by ipfw. This seems a useful behaviour, but it must be documented very clearly because it is not completely intuitive. Perhaps we should find a more descriptive name. Good progress! cheers luigi
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