Date: Wed, 26 Mar 2003 19:33:51 +0100 From: Maxime Henrion <mux@freebsd.org> To: Mike Silbersack <silby@silby.com> Cc: cvs-src@FreeBSD.org Subject: Re: cvs commit: src/sys/conf options src/sys/netinet ip_output.c Message-ID: <20030326183351.GJ57674@elvis.mu.org> In-Reply-To: <20030326114030.U2075@odysseus.silby.com> References: <200303260452.h2Q4quap015364@www.ambrisko.com> <20030326114030.U2075@odysseus.silby.com>
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Mike Silbersack wrote: > > On Tue, 25 Mar 2003, Doug Ambrisko wrote: > > > | I think that we'll end up being even better off by just making a > > | m_defragment function, thereby reducing code duplication even more. I'll > > | make sure to test any such function more than I tested the MBUF_FRAG_TEST > > | code, however. :) > > > > Yes, I was thinking that as well. > > Ok, here's my attempt at a m_defragment function. It seems to work well > here, although I have only tested it with the if_xl driver. Could you > guys give it a quick lookover to see if it has any bugs? I'll add the > ability to copy mbuf chains longer than MCLBYTES once I know all the > packet header handling / etc is correct. > > Also note that the patch contains my changes to if_xl, which are mostly > debugging code. You can ignore most of that. One change I _will_ make to > if_xl, however, is to walk the chain and find out its length _before_ we > do any busdma calls; this moves the defragmentation occur earlier, thereby > avoiding the need for a complex error recovery case. I suspect we'll want > to do the same in the other network drivers. Nice work! This will really be very useful to have for the network interface drivers. I have a few comments : - You removed the m_getcl() optimization that has been added in if_xl.c recently. You should use m_getcl() if len is > MHLEN, because m_getcl() grabs both a header and a cluster. If len is <= MHLEN, you can just use m_gethdr(). I guess you did this because you have been hitting the KASSERT() in m_dup_pkthdr(), and I think this KASSERT() is a bit bogus. It seems to me there should be a way to do it without having to delay the cluster allocation. Maybe Sam or Robert could comment on this? - I believe an mbuf chain passed to a network driver should always have a packet header. - Minor style(9) nits: you should test pointers against NULL and not using them as booleans. Also, there's a trailing newline in the m_defragment() function. Thanks for doing this work! Cheers, Maxime
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