Date: Mon, 19 Sep 2005 08:16:26 -0700 From: Luigi Rizzo <rizzo@icir.org> To: Brett Glass <brett@lariat.org> Cc: net@freebsd.org Subject: Re: Efficient use of Dummynet pipes in IPFW Message-ID: <20050919081626.B67259@xorpc.icir.org> In-Reply-To: <6.2.3.4.2.20050919085600.07f783f0@localhost>; from brett@lariat.org on Mon, Sep 19, 2005 at 09:11:33AM -0600 References: <6.2.3.4.2.20050918205708.08cff430@localhost> <20050918235659.B60185@xorpc.icir.org> <6.2.3.4.2.20050919010035.07dfc448@localhost> <20050919005932.B60737@xorpc.icir.org> <6.2.3.4.2.20050919085600.07f783f0@localhost>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, Sep 19, 2005 at 09:11:33AM -0600, Brett Glass wrote: > At 01:59 AM 9/19/2005, Luigi Rizzo wrote: > > >Same for as the 'resume' option. It might be nice to have, > >however but there is already a two-rule version (the one i > >suggested, follow the non-terminating action with a skipto rule) > >so its absence is not blocking you from doing what you want. > > That option requires repeating ALL of the matching on the packet. absolutely not. it is the same as your 'resume' only split on two lines. > >in terms of implementation, if you want to add it, the best place > >would be to add the 'skipto' fields to each 'action' opcode. > >I am not very interested in implementing it, though, because i still see > >ipfw as a low-level language. > > I don't see it that way, because low level languages like assembler > are normally very efficient and highly granular. The underlying > opcode language of IPFW is low level for sure. But I would classify > IPFW's "language," as presented by the userland utility, as "high > level but limited." Sort of like the MS-DOS shell. whatever. feel free to write a high level interpreter, since i don't see it that way you can't expect me to do that :) cheers luigi > >> I've looked at the source and it's fragmented and virtually undocumented, > > > >are you talking about the userland part or the kernel code ? > > Both. There are some parts that are better than others; for > example, the kernel part is more straightforward than the > userland part and has more comments. > > Yes, I know: some coders (the NetBSD folks are notorious for this) > seem to think that if you don't want to read (and mentally reverse- > engineer) all of the C code, you shouldn't be touching it. But this > leads to bugs, because even a good coder won't know about "contracts" > involving code in other places. > > >i agree the userland part is a mess. > >But the kernel code i believe is reasonably documented > >(of course it could be documented better - patches welcome). > >the first 250 or so lines in ip_fw2.h are almost all comments > >describing the opcode formats. > >ip_fw2.c tries to describe rule parsing in the body of ipfw_chk() > > Yep, I see that. But there are implicit contracts with the userland > side.... Some are obvious but some seem to be subtle. > > --Brett Glass
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050919081626.B67259>