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Subject: Re: Re: CAS: partial (damaged?) UDP msg
From: "Zhang Yuliang" <zhangyl@ihep.ac.cn>
To: "Michael Davidsaver" <mdavidsaver@gmail.com>, shen@frib.msu.edu
Cc: tech-talk <tech-talk@aps.anl.gov>
Date: Mon, 17 Apr 2017 12:04:38 +0800 (GMT+08:00)
Hi Michael and Guobao

10.1.204.140 is the CA clients host, which runs CSS using CAJ.
The C# CAS and Labvies CAS run on different Window7 machines. Yes, these CA servers were all started ok.
From saturday to now, there is no CA server hung up event occurs anymore and that softIOC does not output these message again. 

Yuliang

> -----原始邮件-----
> 发件人: "Michael Davidsaver" <mdavidsaver@gmail.com>
> 发送时间: 2017年4月16日 星期日
> 收件人: "Zhang Yuliang" <zhangyl@ihep.ac.cn>, tech-talk <tech-talk@aps.anl.gov>
> 抄送: 
> 主题: Re: CAS: partial (damaged?) UDP msg
> 
> I've seen messages like this pop up occasionally with no apparent ill
> effects.
> 
> What is 10.1.204.140?  Is this host expected to run CA clients?  If so,
> which implementation(s)?  Something other than libca or CAJ?
> 
> On 04/15/2017 07:27 AM, Zhang Yuliang wrote:
> > Hi all,
> > 
> > I found that one soft ioc output the following information:
> > 
> > epics> CAS: partial (damaged?) UDP msg of 8 bytes from 10.1.204.140:54439 ?
> 
> The shortest valid CA message is 16 bytes.  So any packet set to UDP
> port 5064 with length 8 is clearly invalid.  Practically, CA search
> broadcasts will have more than 32 bytes.  A Version message and at least
> one Search message with a non-zero payload.
> 
> FYI http://www.aps.anl.gov/epics/base/R3-16/0-docs/CAproto/index.html
> 
> > 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
> 
> This looks like bytes 8-24 of a search message with a searchID 0xc1c for
> a PV name beginning with "ACC_LRBT".
> 
> Very odd.  It appears that a CA search packet is getting split into two
> packets at offset 8.  I don't know how this could happen.
> 
> ...
> > At that time, all of our Labview and C# type CA servers hung up(the standard iocs were all ok), no response to the ca search from clients. After we reboot the ca servers, it return to OK.
> > It is the first time we saw this and I think the ca server hung up event has relation to the invalid request.
> 
> If these are only CA servers, then I suspect that these hangs are an
> effect, not the cause.  Probably improper handling of truncated search
> messages.
> 


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

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