sparc64/80410: netgraph is causing crash with mpd on sparc64

[Sten Spans]

On Wed, 27 Apr 2005, Andrew Belashov wrote:

>
>> Description:
> 	mpd does not work on FreeBSD/sparc64. Kernel panic with "memory address
> not aligned" trap message.
>
>> How-To-Repeat:
> 	Configure and run mpd for VPN over pptp. After connect to VPN,
> start nmap scanner. Kernel right away crashed. I have coredump:
>

Finding unaligned ( or rather not 64bit aligned ) mbufs is the
new cool thing, try if_em or if_tap for more fun and games :).

On a more serious note, the main problem is that l3 protocols
( ip, ipv6, ipx ) expect their data to be aligned a certain way.

But newer ethernet cards, complex headers, complex tunneling
tricks, etc often shift contents a few bytes. i386 has no alignment 
constraints ( a small speed hit though ) which means that these
problems are often overlooked.

OpenBSD and NetBSD have quite a few dirty hacks in drivers to
fixup the mess for each driver. Some work has been done with
m_copyup in -CURRENT but the debate is still open on wether
this should be fixed in a general way in l3 protocols, or in
each "ethernet" driver, or even somewhere else entirely.

HTH HAND

-- 
Sten Spans

"There is a crack in everything, that's how the light gets in."
Leonard Cohen - Anthem