[ALTQ/FreeBSD] Re: Pagefault with bpf

[Vlad Galu <vladg@xxxxxxxxx>]

On Sat, 19 Apr 2003 02:48:03 +0200
"Max Laier" <max@love2party.net> wrote:

> Some time ago I wrote:
> > I gave ALTQ a try on my 5.0-Release Laptop with Intel
> > fxp Ethernet. Worked fine until I tried to look at my
> > traffic with "tcpdump -i fxp0" and a
> packet
> > was droped, as this caused my kernel to panic with
> > "pagefault in
> kernelmode"
> > and a trace like this:
> >
> > < TRACE ...
> > < bpf_mtap
> > < fxp_start
> > < fxp_intr_body
> > < fxp_intr
> > < ithread_loop
> > < fork_exit
> > < fork_trampoline
> >
> > I could attach dmesg and stuff (if you really want it)
> > but it seems that this is a more general problem. bpf
> > just does not exspect a freed mbuf so early and hence
> > does not capture it. Can you think of any workaround or
> fix
> > for this issue, maybe there is a LOCK for that? Please
> > let me know.
> >
> > Regards,
> >     Max
> 
> but didn't get any response here until now. I discussed
> the problem with Pyun YongHyeon, who is working on the pf
> port(http://pf4freebsd.love2party.net/) and he came up
> with the following:
> 
> < After reading NetBSD/OpenBSD's fxp driver, I realized
> there is some< missing lines in FreeBSD ALTQ fxp driver.
> < Anyway, here is patch.
> 
> monster# diff -u if_fxp.c if_fxp.c.mod
> --- if_fxp.c    Mon Apr  7 17:05:19 2003
> +++ if_fxp.c.mod        Tue Apr 15 14:12:22 2003
> @@ -1039,7 +1039,8 @@
>                  * Grab a packet to transmit.
>                  */
>                 IFQ_DEQUEUE(&ifp->if_snd, mb_head);
> -
> +               if (mb_head == NULL)
> +                       break;
>                 /*
>                  * Get pointer to next available tx desc.
>                  */
> 
> He told me that he reported to Adrian Penisoara, but
> didn't get any response either. So I just decided to
> report here (in case somebody reads the list and has come
> across this error)
> 
> Regards
>     Max
> 
> p.s. ALTQ-Support with our pf port is evolving. Have a
> loot at http://pf4freebsd.love2party.net/
> 
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> 

	Thanks a lot, that helped. I appreciate your good will.

	All my best,

------------
Vlad Galu
Network Administrator VipNET Bucharest
tel: 021/4114262
email: vladg@vipnet.ro
web: http://www.vipnet.ro

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