Date: Wed, 24 Nov 2010 13:59:47 +1300 From: Andrew Thompson <thompsa@FreeBSD.org> To: Jung-uk Kim <jkim@freebsd.org> Cc: Weongyo Jeong <weongyo@freebsd.org>, freebsd-usb@freebsd.org Subject: Re: [RFC] USBdump patches Message-ID: <AANLkTi=D5Spta67JfA%2BSXh2VF8dDV_aKN%2BgHYF01Znb4@mail.gmail.com> In-Reply-To: <201011231936.57818.jkim@FreeBSD.org> References: <AANLkTinaUNi3FGRiOkeTN2FKx3ybqE=F3W6%2BsV8qVCTf@mail.gmail.com> <201011231852.40484.jkim@FreeBSD.org> <20101124001832.GI92881@weongyo> <201011231936.57818.jkim@FreeBSD.org>
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On 24 November 2010 13:36, Jung-uk Kim <jkim@freebsd.org> wrote: > On Tuesday 23 November 2010 07:18 pm, Weongyo Jeong wrote: >> - BPF was normally for ethernet frames (most operations were >> based on mbuf including the machine filter and there were a lot of >> assumptions the input buffer is mbuf type. For example, handling >> BPF_LD|BPF_W|BPF_ABS). However the USB packet isn't like mbuf >> style that it's just a linear buffer. So the most important code >> or assumption wasn't compatible. > > BPF can deal with linear buffer just fine. For example, ng_bpf(4) > does it. Please see sys/netgraph/ng_bpf.c. > >> - Just making the patch for BPF code, it looked like a trick or >> a hack to me because I couldn't define what BPF should be. > > If you don't want to touch bpf.c for some reason, netgraph(4) (-> > ng_bpf) may be an alternate solution for you. > >> - I could not define BPF exactly myself that what BPF should >> cover. I agreed with that BPF is for ethernet packet filtering but >> could not make sure myself that BPF could cover USB packets. > > BPF is a generic packet filter machine, i.e., bytecode is generic > enough for any type of data stream. I agree that this is the best way forward, if it can be achieved. Andrewhome | help
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