Date: Wed, 17 May 1995 11:40:01 -0700 From: Bill Fenner <fenner@parc.xerox.com> To: freebsd-bugs Subject: kern/429: de driver BPF/Multicast logic broken Message-ID: <199505171840.LAA11126@freefall.cdrom.com> In-Reply-To: Your message of Wed, 17 May 1995 11:26:38 PDT <199505171826.LAA01469@baobab.parc.xerox.com>
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>Number: 429
>Category: kern
>Synopsis: de driver BPF/Multicast logic is broken
>Confidential: no
>Severity: critical
>Priority: high
>Responsible: freebsd-bugs (FreeBSD bugs mailing list)
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed May 17 11:40:00 1995
>Originator: Bill Fenner
>Organization:
Xerox PARC
>Release: FreeBSD 2.1.0-Development i386
>Environment:
FreeBSD-2.0 SNAP-950412, although I checked -current as of
5/16/95 and it was not fixed. I assume that -current is
the 2.0.5 tentative release.
i386/config/FENESTRO has:
device de0
pseudo-device bpfilter16
>Description:
if_de.c's BPF/multicast logic is broken. It goes something like:
#if BPF is configured
if there is a BPF listener
send the packet to BPF
If it was a packet I normally wouldn't get, then just drop it
else if there is no BPF listener
If this packet is not for me and not broadcast,
just drop it (i.e. if it is multicast, drop it!)
#endif
This means that if BPF is configured, but there are no BPF listeners,
you don't get any multicast.
>How-To-Repeat:
On a machine on the MBONE with a de card and bpfilter in the kernel,
run "vat" and notice that you get no names showing up in the name
window. Leave the "vat" running and start a "tcpdump", and notice
the name window fill up. Kill the "tcpdump" and watch all the names
gray out.
>Fix:
The reason for the checks is because BPF might decide to put the interface
in promiscuous mode. Therefore,
a) if there are no BPF listeners, there is no need to do this checking
b) can optimize out the ethernet address comparisons by checking IFF_PROMISC
I have been running this fix for two weeks and haven't had any problems,
running multicast apps and tcpdump at the same or different times.
*** if_de.c.orig Wed May 3 08:36:36 1995
--- if_de.c Wed May 3 08:37:47 1995
***************
*** 567,577 ****
#if NBPFILTER > 0
if (sc->tulip_bpf != NULL) {
bpf_tap(sc->tulip_bpf, mtod(m, caddr_t), total_len);
! if ((eh.ether_dhost[0] & 1) == 0 &&
!TULIP_ADDREQUAL(eh.ether_dhost, sc->tulip_ac.ac_enaddr))
- goto next;
- } else if (!TULIP_ADDREQUAL(eh.ether_dhost, sc->tulip_ac.ac_enaddr)
- && !TULIP_ADDRBRDCST(eh.ether_dhost)) {
goto next;
}
#endif
--- 567,575 ----
#if NBPFILTER > 0
if (sc->tulip_bpf != NULL) {
bpf_tap(sc->tulip_bpf, mtod(m, caddr_t), total_len);
! if (sc->tulip_if.if_flags & IFF_PROMISC &&
! (eh.ether_dhost[0] & 1) == 0 &&
!TULIP_ADDREQUAL(eh.ether_dhost, sc->tulip_ac.ac_enaddr))
goto next;
}
#endif
>Audit-Trail:
>Unformatted:
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