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Subject: Re: CAS: partial (damaged?) UDP msg
From: Michael Davidsaver <mdavidsaver@gmail.com>
To: Zhang Yuliang <zhangyl@ihep.ac.cn>, tech-talk <tech-talk@aps.anl.gov>
Date: Sun, 16 Apr 2017 17:25:33 -0400
On 04/16/2017 10:46 AM, Michael Davidsaver wrote:
> On 04/16/2017 10:39 AM, Michael Davidsaver wrote:
>>> CAS: request from 10.1.204.140:54439 => CAS: Missaligned protocol rejected
>>> CAS: Request from 10.1.204.140:54439 => cmmd=0 cid=0x4143435f type=0 count=3100 postsize=3100
>>> CAS: Request from 10.1.204.140:54439 =>   available=0x4c524254 	N=3 paddr=(nil)
>> The offending header was:
>>
>>> 00000c1c 00000c1c 4143435f 4c524254
> 
> Also the N=3 indicates that other this is the 4th message in the UDP
> packet and the the previous 3 were considered valid.
> 
> The seems like a client is not constructing UDP packets properly.

I think I see what is happening.  CA requires that every message size be
a multiple of 8 bytes.  This should be done by padding with zeros and
adjusting the message size field.  This CA client is inconsistent with
padding when packing multiple messages into one UDP packet.

> CAS: partial (damaged?) UDP msg of 8 bytes from 10.1.204.140:54439 ?

In this case a message size field is too short, so there are 8 bytes
left over at the end of the packet.

>>> CAS: request from 10.1.204.140:54439 => CAS: Missaligned protocol
rejected

In this case a message size field is too long, so the preceding message
(N=2) body contained the first 8 bytes of the next message.


References:
CAS: partial (damaged?) UDP msg Zhang Yuliang
Re: CAS: partial (damaged?) UDP msg Michael Davidsaver
Re: CAS: partial (damaged?) UDP msg Michael Davidsaver

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