Date: Mon, 2 May 2005 11:09:10 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Maksim Yevmenkin <maksim.yevmenkin@savvis.net> Cc: net@freebsd.org Subject: Re: if_tap unaligned access problem Message-ID: <20050502180910.GV2670@funkthat.com> In-Reply-To: <42765799.6090201@savvis.net> References: <20050428135120.GB21428@cell.sick.ru> <427111BF.2050607@savvis.net> <42712BAA.4070201@elischer.org> <42715269.3010306@errno.com> <Pine.SOC.4.61.0504291132520.28551@tea.blinkenlights.nl> <4272743A.2030003@savvis.net> <20050429182819.GP2670@funkthat.com> <42765799.6090201@savvis.net>
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Maksim Yevmenkin wrote this message on Mon, May 02, 2005 at 09:38 -0700:
> >>>>>>i think we have few options here:
> >>>>>>
> >>>>>>1) revert back original tapwrite function that was changed in v.
> >>>>>>1.48 and set offset to 2 bytes in top mbuf
> >>>>>>
> >>>>>>2) change current version of tapwrite so it would m_prepend and
> >>>>>>m_pullup mbuf after m_uiotombuf
> >>>>>>
> >>>>>>3) change m_uiotombuf to accept one more parameter - mbuf offset at
> >>>>>>which data should be copied. there are not that many users of
> >>>>>>m_uiotombuf
> >>
> >>please find and review the attached patch (untested) that implements
> >>option (3) above.
>
> any objections to the attached (revised) patch? can i commit it?
>
> thanks,
> max
> Index: sys/kern/uipc_mbuf.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/kern/uipc_mbuf.c,v
> retrieving revision 1.147
> diff -u -r1.147 uipc_mbuf.c
> --- sys/kern/uipc_mbuf.c 17 Mar 2005 19:34:57 -0000 1.147
> +++ sys/kern/uipc_mbuf.c 2 May 2005 16:33:41 -0000
> @@ -1333,7 +1333,7 @@
> #endif
>
> struct mbuf *
> -m_uiotombuf(struct uio *uio, int how, int len)
> +m_uiotombuf(struct uio *uio, int how, int len, int align)
> {
> struct mbuf *m_new = NULL, *m_final = NULL;
> int progress = 0, error = 0, length, total;
> @@ -1342,12 +1342,15 @@
> total = min(uio->uio_resid, len);
> else
> total = uio->uio_resid;
> - if (total > MHLEN)
> + if (align >= MHLEN)
> + goto nospace;
> + if (total + align > MHLEN)
I kinda noticed this a bit ago, but didn't think much of it till now...
do we want to allow align >= MHLEN if total requires a cluster? since
if we use a cluster, we'd have enough space for a larger align...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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