Re: [bug found] Re: byte swapped udp length in diskless bootp request ?

On Friday 01 December 2006 13:08, Luigi Rizzo wrote:
> On Thu, Nov 30, 2006 at 10:55:37AM -0800, Luigi Rizzo wrote:
> > i was just trying to diskless-boot a -current kernel,
> > and when it was time for the kernel to acquire the address
> > i was getting the usual
> > 
> > 	DHCP/BOOTP timeout for server 255.255.255.255
> > 
> > Usually it is because of lack of connectivity, but
> > a bit of inspection on the server showed (as you can see
> > below) that the UDP len field is byte-swapped - the 05bc
> > in the packet is in little-endian format, causing the
> > server to reject it.
> 
> [ actually, it is the IP len that is byte-swapped ]
> 
> > I am trying to follow the code in sys/nfsclient/bootp_subr.c
> > (which should send the packet) but it seemd to call sosend()
> > (at line 755) to generate the packet, so it looks really strange
> > that the bug is in such a central place... any ideas ?
> 
> as a followup:
> 
>     Downgrading sys/kern/uipc_socket.c to version 1.284 make HEAD
>     work again with in-kernel bootp..
> 
> i managed to locate the bug in the following commit:
> 
> 
http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/kern/uipc_socket.c.diff?r1=1.284&r2=1.285
> 
>   Revision 1.285  Thu Nov 2 17:45:28 2006 UTC (4 weeks ago) by andre
>   Branch: MAIN
>   Changes since 1.284: +29 -1 lines
>   Diff to previous 1.284 (colored)
> 
>   Use the improved m_uiotombuf() function instead of home grown 
sosend_copyin()
>   to do the userland to kernel copying in sosend_generic() and 
sosend_dgram().
> 
>   sosend_copyin() is retained for ZERO_COPY_SOCKETS which are not yet 
supported
>   by m_uiotombuf().
> 
> I don't know exactly where the problem is, but the bug i found is triggered
> by in-kernel sockets (such as the one used by the internal bootp client)
> so maybe this was a case not tested by andre.
> 
> I am unclear on where is the actual bug. hopefully something simple...

Does the bootp code try to send a 0 byte packet per chance?

-- 
John Baldwin