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Date: Sat, 9 Feb 2002 16:19:57 +0100 (CET)
From: "Simon 'corecode' Schubert" <corecode@corecode.ath.cx>
Reply-To: "Simon 'corecode' Schubert" <corecode@corecode.ath.cx>
To: FreeBSD-gnats-submit@freebsd.org
Cc:
Subject: bad tcp chksum on certain ips
X-Send-Pr-Version: 3.113
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>Number:         34756
>Category:       kern
>Synopsis:       bad tcp chksum on certain ips
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Feb 09 07:30:00 PST 2002
>Closed-Date:    Sat Feb 9 16:35:34 PST 2002
>Last-Modified:  Sat Feb 09 16:35:53 PST 2002
>Originator:     Simon 'corecode' Schubert
>Release:        FreeBSD 4.5-STABLE i386
>Organization:
>Environment:
System: FreeBSD elevation.zuhause.stoert.net 4.5-STABLE FreeBSD 4.5-STABLE #2: Sat Feb 9 14:06:54 CET 2002 corecode@elevation.zuhause.stoert.net:/usr/obj/i386/k7/usr/src/sys/ELEVATION i386

cvsupped every day 02:00 CET. this world+kernel compiled right now.

	
>Description:
Trying to connect to www.farnell.com results timeouts. tcpdump reveils:


Script started on Sat Feb  9 16:07:26 2002
# tcpdump -nelpvvvxXi ed0 host www.farnell.com & telnet www.farnell.com 80
Trying 194.152.77.229...
tcpdump: listening on ed0
16:07:31.710610 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 74: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 76276 0> (DF) [tos 0x10]  (ttl 64, id 3108, len 60)
0x0000	 4510 003c 0c24 4000 4006 1b34 c0a8 422e	E..<.$@.@..4..B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 a002 ffff 8edf 0000 0204 05b4 0103 0301	................
0x0030	 0101 080a 0001 29f4 0000 0000          	......).....
16:07:34.710878 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 74: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460,nop,wscale 1,nop,nop,timestamp 76576 0> (DF) [tos 0x10]  (ttl 64, id 3118, len 60)
0x0000	 4510 003c 0c2e 4000 4006 1b2a c0a8 422e	E..<..@.@..*..B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 a002 ffff 8db3 0000 0204 05b4 0103 0301	................
0x0030	 0101 080a 0001 2b20 0000 0000          	......+.....
16:07:37.711112 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 58: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460> (DF) [tos 0x10]  (ttl 64, id 3127, len 44)
0x0000	 4510 002c 0c37 4000 4006 1b31 c0a8 422e	E..,.7@.@..1..B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 6002 ffff 05f4 0000 0204 05b4          	`...........
16:07:40.711373 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 58: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460> (DF) [tos 0x10]  (ttl 64, id 3137, len 44)
0x0000	 4510 002c 0c41 4000 4006 1b27 c0a8 422e	E..,.A@.@..'..B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 6002 ffff 05f4 0000 0204 05b4          	`...........
16:07:43.711623 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 58: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460> (DF) [tos 0x10]  (ttl 64, id 3152, len 44)
0x0000	 4510 002c 0c50 4000 4006 1b18 c0a8 422e	E..,.P@.@.....B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 6002 ffff 05f4 0000 0204 05b4          	`...........
16:07:49.712113 0:60:52:0:23:3a 0:60:52:0:d5:31 0800 58: 192.168.66.46.1044 > 194.152.77.229.80: S [bad tcp cksum fffe!] 595220480:595220480(0) win 65535 <mss 1460> (DF) [tos 0x10]  (ttl 64, id 3183, len 44)
0x0000	 4510 002c 0c6f 4000 4006 1af9 c0a8 422e	E..,.o@.@.....B.
0x0010	 c298 4de5 0414 0050 237a 5800 0000 0000	..M....P#zX.....
0x0020	 6002 ffff 05f4 0000 0204 05b4          	`...........
^C# ^D
Script done on Sat Feb  9 16:08:10 2002

this happened in my previous world+kernel (from mid-january), too.
i can't reproduce this problem on another fbsd (4.4-STABLE) machine.

a quick check showed, that not only this ip address is affected:
it *appears* that 194.152.77.209 still works (tcp chksum ok), .210 to .255 not.
somehow every ip address that got its last byte above 209 produces a chsum error.

very strange.

	
>How-To-Repeat:
try to establish a tcp connection to a host where the last byte of its ip address is 210 or above.

	
>Fix:
if i knew.

	


>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->closed 
State-Changed-By: cjc 
State-Changed-When: Sat Feb 9 16:35:34 PST 2002 
State-Changed-Why:  
Submitter reports the problems was due to compiler bugs when using 
optimization settings -O2 and above. No problem when -O 
used. Submitter asks PR be closed. 

http://www.FreeBSD.org/cgi/query-pr.cgi?pr=34756 
>Unformatted:
