>Number:         32346
>Category:       kern
>Synopsis:       SACK causes panic under heavy load
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 21 07:35:00 +0000 2005
>Originator:     Anders Magnusson
>Release:        NetBSD 3.99.3
>Organization:
LTU
>Environment:
NetBSD news.stupi.se 3.99.3 NetBSD 3.99.3 (GENERIC) #38: Fri May 27 09:50:10 CEST 2005  ragge@ulrik.dc.luth.se:/home/ragge/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
On a heavy loaded news spool machine, the newly added SACK code causes panics sometimes.  See stack trace:

db> bt
cpu_Debugger() at netbsd:cpu_Debugger+0xa
panic() at netbsd:panic+0x1cd
m_copydata() at netbsd:m_copydata+0xae
tcp_build_datapkt() at netbsd:tcp_build_datapkt+0x272
tcp_output() at netbsd:tcp_output+0x11ce
tcp_sack_newack() at netbsd:tcp_sack_newack+0x134
tcp_input() at netbsd:tcp_input+0x15d1
ip_input() at netbsd:ip_input+0x560
ipintr() at netbsd:ipintr+0x9b
DDB lost frame for netbsd:Xsoftnet+0x4a, trying 0xffffffff809cbd10
Xsoftnet() at netbsd:Xsoftnet+0x4a
--- interrupt ---

Unfortunately I haven't been able to do any serious debugging on this, the machine needs to be up and running.

>How-To-Repeat:
Run a heavy loaded news machine.  This do not happen often.
>Fix:
Disable sack makes the machine stable again.