Date: Mon, 10 Jun 1996 16:43:35 -0700 From: Jason Thorpe <thorpej@nas.nasa.gov> To: Ted Lemon <mellon@fugue.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Swapped ethertype in BPF output? Message-ID: <199606102343.QAA19007@lestat.nas.nasa.gov>
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On Mon, 10 Jun 1996 16:05:18 -0700
Ted Lemon <mellon@fugue.com> wrote:
> I'm the author of the Internet Software Consortium DHCP server. One
> of the operating systems on which ISC dhcpd is supported is FreeBSD.
> A FreeBSD user has reported a problem in that on FreeBSD, BPF
> apparently swaps the ethertype supplied by the user program when
> sending a packet. If true, this breaks code in dhcpd that works on
> all other platforms that support BPF, including NetBSD, BSD/OS, and
> DEC Alpha OSF/1.
>
> Is this user correct, and if so, is this a known bug that is going to
> be fixed, or a ``feature''? The FreeBSD port is completely clean
> other than this, and I would really prefer not to have to put in an
> ifdef for something like this.
Hi Ted ... long time no see :-)
It's not just the ethertype, from what I can tell...See the following
kludge in NetBSD's rbootd(8) (the HP Remote Maintainance Protocol boot
server):
int
SendPacket(rconn)
register RMPCONN *rconn;
{
/*
* Set Ethernet Destination address to Source (BPF and the enet
* driver will take care of getting our source address set).
*/
bcopy((char *)&rconn->rmp.hp_hdr.saddr[0],
(char *)&rconn->rmp.hp_hdr.daddr[0], RMP_ADDRLEN);
#ifdef __FreeBSD__
/* BPF (incorrectly) wants this in host order. */
rconn->rmp.hp_hdr.len = rconn->rmplen - sizeof(struct hp_hdr);
#else
rconn->rmp.hp_hdr.len = htons(rconn->rmplen - sizeof(struct hp_hdr));
#endif
/*
* Reverse 802.2/HP Extended Source & Destination Access Pts.
*/
rconn->rmp.hp_llc.dxsap = htons(HPEXT_SXSAP);
rconn->rmp.hp_llc.sxsap = htons(HPEXT_DXSAP);
[ . . . ]
It's been there ever since Mike Hibler and I helped a fellow recover a
fairly dead HP-BSD system ... the guy ended up netbooting NetBSD/hp300,
mounting his HP-BSD filesystems, and recovering his data (darn, those old
HP-IB drives :-) All the guy had was a NeXT and a PC on which he could
install FreeBSD (happened to have a 2.0.5 CD laying around...)
I don't know if it's a bug or feature (and, am not really willing to make
a guess either way :-), but just wanted to point out that it seems as if
the packet length needs to be in the wrong order, too...
----save the ancient forests - http://www.bayarea.net/~thorpej/forest/----
Jason R. Thorpe thorpej@nas.nasa.gov
NASA Ames Research Center Home: 408.866.1912
NAS: M/S 258-6 Work: 415.604.0935
Moffett Field, CA 94035 Pager: 415.428.6939
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