Re: [PATCH] netfilter ulog byte alignment problem

[Fabian Hugelshofer <hugelshofer2006@gmx.ch>]

Patrick McHardy wrote:
> Fabian Hugelshofer wrote:
>> I tracked the issue down to a byte alignment problem in
>> ulog_packet_msg_t (include/linux/netfilter_ipv4/ipt_ULOG.h). Setting
>> attributes 'packed' or 'aligned' or using 'size_t' instead of 'unsigned
>> char' for field 'mac_len' solved the problem. It seems necessary to help
>> the compiler doing things right.
[...]
> I'm afraid it might break compatibility on other architectures.
> Are your userspace and kernel compiled using the same options?
> Why would they lay out the structure differently?

I think you are right. The compiler lays it out consistantly while
respecting proper alignment. I removed my patch again and it worked
event without. I think the reason was header files which were out of 
sync (kernel vs. userspace). I had to modify ipt_ULOG.(c|h) for a driver 
problem workaround. I'm quire sure that I reverted the changes during 
the testing, but maybe I missed that.

I would write again, if the problem reappears later.