The following reply was made to PR kern/30160; it has been noted by GNATS.

From: Geoff Wing <gcw@pobox.com>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: kern/30160: TCP SACK code causes 'panic: m_copydata: m == 0, len 1'
Date: Sat, 7 May 2005 12:45:52 +1000

 On Saturday 2005-05-07 09:13 +1000, jmcneill@NetBSD.org output:
 :Periodically, two of my machines (running completely different workloads) will
 :die with 'panic: m_copydata: m == 0, len 1'. One is an MP sparc, the other is
 :a UP alpha.
 :
 :Disabling sack makes the problem disappear:
 :  sysctl -w net.inet.tcp.sack=0
 :  sysctl -w net.inet6.tcp6.sack=0
 
 Note the sysctl names have changed in current.  net.inet.tcp.sack is now a
 node not a leaf.  e.g. the first one is now  net.inet.tcp.sack.enable
 
 A backtrace on i386 around 7th March:
 
 panic: m_copydata: m == 0, len 1
 Begin traceback...
 m_copydata(0,0,1,c143897c,c1472d18) at netbsd:m_copydata+0x81
 tcp_build_datapkt(c1ba48fc,c147c1c0,65a,1,34) at netbsd:tcp_build_datapkt+0x229
 tcp_output(c1ba48fc,cc467e10,c16df208,caf1c824,c1ba48fc) at netbsd:tcp_output+0xd6b
 tcp_sack_newack(c1ba48fc,caf1c824,cc467f08,caf1c838,1) at netbsd:tcp_sack_newack+0xed
 tcp_input(c1462b00,14,6,c16dfe08,c1462b00) at netbsd:tcp_input+0x146a
 ip_input(c1462b00,0,0,200246,0) at netbsd:ip_input+0x53f
 ipintr(1f,bfbf001f,1f,bfbf001f,85ea2dc) at netbsd:ipintr+0x76
 DDB lost frame for netbsd:Xsoftnet+0x41, trying 0xcc467fa8
 Xsoftnet() at netbsd:Xsoftnet+0x41
 --- interrupt ---
 0x200202:
 End traceback...