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Date: Tue, 8 May 2007 19:21:07 GMT
From: Seraphi<seraphi.lord@gmail.com>
To: freebsd-gnats-submit@FreeBSD.org
Subject: NFS over TCP under load hangs with "impossible packet length"
X-Send-Pr-Version: www-3.0

>Number:         112528
>Category:       kern
>Synopsis:       [nfs] NFS over TCP under load hangs with "impossible packet length"
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-net
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue May 08 19:30:05 GMT 2007
>Closed-Date:    
>Last-Modified:  Sat Sep 15 22:40:01 GMT 2007
>Originator:     Seraphi
>Release:        6.2-RELEASE-p4
>Organization:
>Environment:
FreeBSD nfsclient05.domain.com 6.2-RELEASE-p4 FreeBSD 6.2-RELEASE-p4 #0: Tue May  8 13:59:19 EDT 2007     admin@nfsclient05.domain.com:/usr/obj/usr/src/sys/MYKERN_62_05042007  amd64
>Description:
NFS over UDP will hang under load and throw the following errors to syslog:
May  8 14:36:55 nfsclient05 kernel: impossible packet length (13050202) from nfs server 192.168.101.12:/store22
May  8 14:36:56 nfsclient05 kernel: impossible packet length (1669907873) from nfs server 192.168.101.12:/store22
May  8 14:37:01 nfsclient05 kernel: impossible packet length (46381) from nfs server 192.168.101.12:/store22

I have tried many mount options, but here is one set that will have this
problem:

192.168.101.12:/store22       /s22           nfs     ro,-i,-b,-3,-T,-r=16384,-w=16384 0 0

To get the error to occur, I simply copy a multi-gig file from NFS to a
local drive. It happens very frequently.  I have only tried this on gigabit
networks.

The error goes away if I use UDP, which is what I am using until this is fixed.

I have tried this on FreeBSD 6.1 as well and had the same problem. I have
also tried a different NFS server running a different OS on a different
network with a different configuration on different hardware. It did not
help. I have tried updating with freebsd-update but the status is unchanged.

>How-To-Repeat:
Put an NFS client and server on a gigabit network. Mount the server using TCP:
192.168.101.12:/store22       /s22           nfs     ro,-i,-b,-3,-T,-r=16384,-w=16384 0 0

Copy a large file (1GB+) from the NFS mount to a local drive. Do this a
couple of times, then check /var/log/messages
>Fix:
Use UDP:
192.168.101.12:/store22       /s22           nfs     ro,-i,-b,-3,-U,-r=16384,-w=16384 0 0
>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-amd64->freebsd-net 
Responsible-Changed-By: linimon 
Responsible-Changed-When: Sat May 26 06:58:58 UTC 2007 
Responsible-Changed-Why:  
This does not sound amd64-specific. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=112528 

From: "Death Kitten" <shikoneko@gmail.com>
To: bug-followup@FreeBSD.org, seraphi.lord@gmail.com
Cc:  
Subject: Re: kern/112528: [nfs] NFS over TCP under load hangs with "impossible packet length"
Date: Sat, 15 Sep 2007 18:07:12 -0400

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 I get this error as well.
 
 impossible packet length (365132517) from nfs server
 10.10.129.4:/tank/sites/images.domain.org
 impossible packet length (1642561917) from nfs server
 10.10.129.4:/tank/sites/images.domain.org
 impossible packet length (45280) from nfs server
 10.10.129.4:/tank/sites/images.domain.org
 impossible packet length (2937967) from nfs server
 10.10.129.4:/tank/sites/images.domain.org
 %uname -a
 FreeBSD www0.domain.org 6.2-STABLE FreeBSD 6.2-STABLE #0: Sat Apr 28
 20:12:34 CDT 2007     ender@domain.org:/usr/obj/usr/src/sys/DOMAINWWW  i386
 
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 <div><font face="Arial" size="2">I get this error as well.</font></div>
 <div>&nbsp;</div>
 <div><font face="Arial" size="2">impossible packet length (365132517) from nfs 
 server 10.10.129.4:/tank/sites/images.domain.org<br>impossible packet length 
 (1642561917) from nfs server 
 10.10.129.4:/tank/sites/images.domain.org<br>impossible packet length (45280) 
 from nfs server 10.10.129.4:/tank/sites/images.domain.org<br>impossible packet 
 length (2937967) from nfs server 
 10.10.129.4:/tank/sites/images.domain.org<br></font></div>
 <div><font face="Arial" size="2">%uname -a<br>FreeBSD <a href="http://www0.domain.org">www0.domain.org</a> 6.2-STABLE 
 FreeBSD 6.2-STABLE #0: Sat Apr 28 20:12:34 CDT 2007&nbsp;&nbsp;&nbsp;&nbsp; <a href="mailto:ender@domain.org:/usr/obj/usr/src/sys/DOMAINWWW">ender@domain.org:/usr/obj/usr/src/sys/DOMAINWWW</a>&nbsp; 
 i386<br><br><br></font></div>
 
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>Unformatted:
