Date: Mon, 14 Jun 2004 13:28:06 -0400 From: James Housley <jim@Thehousleys.net> To: freebsd-net@FreeBSD.org Subject: Re: Using netgraph for filtering/modifing packets Message-ID: <40CDE026.3040502@Thehousleys.net> In-Reply-To: <Pine.BSF.4.21.0406141016280.30464-100000@InterJet.elischer.org> References: <Pine.BSF.4.21.0406141016280.30464-100000@InterJet.elischer.org>
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[-- Attachment #1 --] Julian Elischer wrote: > > On Mon, 14 Jun 2004, James Housley wrote: > > >>For testing of a product I would like to be able to modify or even drop >>packets based on their content. What I have in mind is forcing the >>packets through a firewall that would redirect all packet to a netgraph >>node that would either pass unchanged, drop or change the contents to >>assist in testing some corner cases in the code. >> >>1) is this something doable with netgraph, I believe it is. > > > yes > > > >>2) what might be a good place to start? Have done some searching, but >>haven't found any example code I thought I could start from. > > > What sort of filter do you need? > > you can pass packets to netgraph from ipfw by diverting them and > openning a divert socket with teh ksocket node.. > > Or you can pick them directly from the network interface > and filter yourself using the 'bpf' node type to select > on something. > or you can use the etf type of node to filter on a particular > ethertype.. > > there are a lot of options but I don't knw your application enough :-) > I have a product that is connected to a PC via eithernet. The product runs FBSD, but I would likely put another FBSD box in the middle. I want to be able modify packets for good and evil based on the data portion of the packet. For example to ocasionally drop a packet that is acking some command. Or send an ack for a command that was never sent. Or just change data to be invalid. Then after messing with the data portion put it back in the queue to be sent, if it wasn't just dropped. Jim -- /"\ ASCII Ribbon Campaign . \ / - NO HTML/RTF in e-mail . X - NO Word docs in e-mail . / \ ----------------------------------------------------------------- jeh@FreeBSD.org http://www.FreeBSD.org The Power to Serve jim@TheHousleys.Net http://www.TheHousleys.net --------------------------------------------------------------------- "Eagles may soar, but weasels don't get sucked into jet engines" -- Anon [-- Attachment #2 --] 0 *H 01 0 + 0 *H #00U 0 *H 0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA0 040131191100Z 050130191100Z0^10UHousley10 U*James10U James Housley1"0 *H jim@thehousleys.net0"0 *H 0 %k7o_tg ?@<_P. Eh;_{)SӻNKH)'M(W_w%ވ,UnJ13{ ㎊t [lBg] ѢbkKZ 3OXmuq2$=d8ݨiܠc[)"(Vln嗛x RE%H%'zm6 ;!nij0$c` wӁX ᝐCs 00.0 U 0jim@thehousleys.net0 U 0 0 *H }Nrx4Ae+d)?O}ibqWSVَ Uր 0QjL*m$A "Vs̱8~`0e&q$5]%ړN00U 0 *H 0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA0 040131191100Z 050130191100Z0^10UHousley10 U*James10U James Housley1"0 *H jim@thehousleys.net0"0 *H 0 %k7o_tg ?@<_P. Eh;_{)SӻNKH)'M(W_w%ވ,UnJ13{ ㎊t [lBg] ѢbkKZ 3OXmuq2$=d8ݨiܠc[)"(Vln嗛x RE%H%'zm6 ;!nij0$c` wӁX ᝐCs 00.0 U 0jim@thehousleys.net0 U 0 0 *H }Nrx4Ae+d)?O}ibqWSVَ Uր 0QjL*m$A "Vs̱8~`0e&q$5]%ړN0?0 0 *H 01 0 UZA10U Western Cape10U Cape Town10U Thawte Consulting1(0&U Certification Services Division1$0"UThawte Personal Freemail CA1+0) *H personal-freemail@thawte.com0 030717000000Z 130716235959Z0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA00 *H 0 Ħ<UsUNʙZ hup [v :aQP 0cZ,p+Z?qV˯< 6$*+w=+>@dקe*TH<a@ dr` 00U 0 0CU <0:08642http://crl.thawte.com/ThawtePersonalFreemailCA.crl0 U 0)U "0 0 10UPrivateLabel2-1380 *H HP . fgCL!6 -6/ P p<ab:~ t%Pb'qW%ݩ9 Oe_N4[5MwV!x!5$ F]_eO1;070i0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA 0 + 0 *H 1 *H 0 *H 1 040614172807Z0# *H 14"jh*D R_(} H0R *H 1E0C0 *H 0*H 0 *H @0+0 *H (0x +71k0i0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA 0z *H 1ki0b1 0 UZA1%0#U Thawte Consulting (Pty) Ltd.1,0*U#Thawte Personal Freemail Issuing CA 0 *H <Nw 8! i |#"=<Y6)(th l$TeE ։ZHRdxG[UlEA}=aq!e'Oplk> W4E~^ ^MP~mAǂ:ahEH}Pv]/ow]yw ) ('o7MH IC, xS[OSI(AMvlY VUeWbM1QĒ//ɒ
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