Network problem - header checksum error -

[Joel Sherrill]

Steve Hunt wrote:

>in_cksum() does work (without the delay).
>
>
>On Mon, 2006-04-17 at 15:29 +0200, Steve Hunt wrote:
>  
>
>>I have found that by changing file
>>cpukit/libnetworking/netinet/ip_output.c - by adding a delay just before
>>in_cksum_hdr(ip) - the checksum is correctly calculated and everything
>>works!!!! so perhaps the header is still being changed by the driver at
>>that time? or is everything in the same thread? perhaps 'ip' is pointing
>>directly to the hardware and the registers are not stable???.
>>
>>    
>>
Is there any possible way you are seeing some type of caching effect?  
PowerPC
systems sometimes get caching issues with NIC drivers in PCI memory space. 

>>Very strange ...  but I have not have had time to investigate further
>>yet - but I will also see if using in_cksum() in place of in_cksum_hdr()
>>fixes (hides) the problem.
>>
>>As a side issue - I noticed that when my delay was by adding a 'printf'
>>I had a quite stable time reported by ping (~2ms) - but when I used
>>usleep() the time for ping to return changed in a cyclical and
>>predictable way from 10ms to 1mS !!!!! - would this be expected?  I will
>>do some more tests.
>>
>>    
>>
If the usleep() requested falls below the clock tick configured, then it 
can't be less than
that.  So a 10msec clock tick means every usleep() < 10 msec will be 
rounded up to 1 tick.

>>By the way, my target system is a pc104+ ... not very fast by modern
>>standards.
>>
>>    
>>
Fast enough to get into trouble. :)

--joel

>>Steve Hunt
>>
>>On Fri, 2006-04-14 at 18:15 +0200, Steve Hunt wrote:
>>    
>>
>>>No - it looks like only the header checksum is wrong.
>>>
>>>On Fri, 2006-04-14 at 16:30 +0200, Sylvain Prestavoine wrote:
>>>      
>>>
>>>>----- Original Message ----- 
>>>>From: "Steve Hunt" <hunt at alceli.ch>
>>>>To: <rtems-users at rtems.com>
>>>>Sent: Friday, April 14, 2006 2:44 PM
>>>>Subject: Network problem - header checksum error -
>>>>
>>>>
>>>>        
>>>>
>>>>>I am having a problem getting rtems to run.  I can boot my application
>>>>>on my pc104 with rtk8139 network chip using pxe boot and grub.
>>>>>
>>>>>However once my application is running (and is therefore now using the
>>>>>rtems network stack not the pxe or grub networking) any packets sent
>>>>>from my system seem to have incorrect header checksum.
>>>>>
>>>>>For instance a ping to the device reports no replies - but ethereal
>>>>>'sniffer' shows the reply packet arriving - but with corrupt header
>>>>>checksum.
>>>>>
>>>>>          
>>>>>
>>>>How are other datas, corrupted or no ?
>>>>Perhaps is an endianness problem ?
>>>>
>>>>--
>>>>-Stan
>>>>
>>>>
>>>>
>>>>        
>>>>
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