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Date: Wed, 9 Mar 2011 12:29:13 GMT
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: freebsd-gnats-submit@FreeBSD.org
Subject: Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session
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>Number:         155407
>Category:       kern
>Synopsis:       [tcp] Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    lstewart
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Mar 09 12:30:11 UTC 2011
>Closed-Date:    Tue Aug 21 00:11:43 UTC 2012
>Last-Modified:  Tue Aug 21 00:11:43 UTC 2012
>Originator:     Slawa Olhovchenkov
>Release:        8.2
>Organization:
>Environment:
FreeBSD mail.haustus.ru 8.2-RC3 FreeBSD 8.2-RC3 #0: Sun Jan 30 06:28:31 UTC 2011     root@mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
Exhausted net.inet.tcp.reass.maxsegments block recovering tcp session
(for this socket and any other socket waiting for retransmited packets).

After exhausted net.inet.tcp.reass.maxsegments allocation new entry in
tcp_reass failed (for this socket and any other socket waiting for
retransmited packets).

        te = uma_zalloc(V_tcp_reass_zone, M_NOWAIT);
        if (te == NULL) {
                TCPSTAT_INC(tcps_rcvmemdrop);
                m_freem(m);
                *tlenp = 0;
                return (0);
        }

That is packet can be reduce reassemble queue dropped.
>How-To-Repeat:
Need high bandwidth-delay channel with high, but rare drop.

After lost incoming TCP segment and before got retranmited this
segment net.inet.tcp.reass.maxsegments exhausted.

Software emulation:

Tuning by http://fasterdata.es.net/fasterdata/host-tuning/freebsd/
sysctl net.inet.tcp.recvspace=1048576
sysctl net.inet.ip.dummynet.pipe_slot_limit=3000
ipfw pipe 1 config delay 300 queue 3000
ipfw add 100 pipe 1 ip from test_hot to me

fetch http://test_host/big_file

After reach 7MB/s: ipfw pipe 1 config delay 300 queue 3000 plr 0.1

>Fix:
Workaround: set net.inet.tcp.reass.maxsegments in /boot/loader.conf to big value.

>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-bugs->freebsd-net 
Responsible-Changed-By: linimon 
Responsible-Changed-When: Wed Mar 9 20:47:14 UTC 2011 
Responsible-Changed-Why:  
Over to maintainer(s). 

http://www.freebsd.org/cgi/query-pr.cgi?pr=155407 
Responsible-Changed-From-To: freebsd-net->lstewart 
Responsible-Changed-By: lstewart 
Responsible-Changed-When: Sat Mar 12 06:48:44 UTC 2011 
Responsible-Changed-Why:  
Grab. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=155407 
State-Changed-From-To: open->patched 
State-Changed-By: lstewart 
State-Changed-When: Wed Jan 25 11:31:21 UTC 2012 
State-Changed-Why:  
Fix has been MFCed to 8.2-STABLE as svn r230534 

http://www.freebsd.org/cgi/query-pr.cgi?pr=155407 
State-Changed-From-To: patched->closed 
State-Changed-By: lstewart 
State-Changed-When: Tue Aug 21 00:11:43 UTC 2012 
State-Changed-Why:  
Issue fixed by patch; no further reports of problem. 

http://www.freebsd.org/cgi/query-pr.cgi?pr=155407 
>Unformatted:
