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Message-Id: <201206081045.q58AjL2r093330@red.freebsd.org>
Date: Fri, 8 Jun 2012 10:45:21 GMT
From: Nikolay Denev <ndenev@gmail.com>
To: freebsd-gnats-submit@FreeBSD.org
Subject: FreeBSD 
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>Number:         168843
>Category:       kern
>Synopsis:       FreeBSD
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Jun 08 10:50:13 UTC 2012
>Closed-Date:    Fri Jun 08 15:40:04 UTC 2012
>Last-Modified:  Fri Jun 08 15:40:04 UTC 2012
>Originator:     Nikolay Denev
>Release:        8.3-STABLE
>Organization:
>Environment:
reeBSD j3.example.com 8.3-STABLE FreeBSD 8.3-STABLE #1: Wed May  9 12:32:48 CEST 2012     root@j3.example.com:/usr/obj/usr/src/sys/KERN-CARP-PF  amd64
>Description:
It seems that our FreeBSD hosts are sending TCP packets with FIN flag and no ACK set, which is triggering
alerts on some firewalls.

[14:31]root@vpn1.location:/home/ndenev# tcpdump -s0 -vni em1 '(tcp[tcpflags] & tcp-ack == 0) && (tcp[tcpflags] & tcp-fin != 0)'
tcpdump: listening on em1, link-type EN10MB (Ethernet), capture size 65535 bytes
15:18:31.771578 IP (tos 0x0, ttl 62, id 44503, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.53083 > Y.Y.Y.Y.9998: Flags [F], cksum 0x29a6 (correct), seq 2205738519, win 65535, length 0
15:22:02.517922 IP (tos 0x0, ttl 62, id 56317, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.37719 > Y.Y.Y.Y.9998: Flags [F], cksum 0x192b (correct), seq 2125215587, win 65535, length 0
15:24:13.215171 IP (tos 0x0, ttl 62, id 36930, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.25125 > Y.Y.Y.Y.9998: Flags [F], cksum 0x6998 (correct), seq 1370309927, win 65535, length 0
15:25:17.010082 IP (tos 0x0, ttl 62, id 61513, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.48897 > Y.Y.Y.Y.9998: Flags [F], cksum 0x16c2 (correct), seq 2650795726, win 65535, length 0
15:29:19.979799 IP (tos 0x0, ttl 62, id 15471, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.31685 > Y.Y.Y.Y.9998: Flags [F], cksum 0x218d (correct), seq 2057063075, win 65535, length 0
15:35:50.005156 IP (tos 0x0, ttl 62, id 27760, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.50568 > Y.Y.Y.Y.9998: Flags [F], cksum 0x6df3 (correct), seq 2102571459, win 65535, length 0
15:38:28.252143 IP (tos 0x0, ttl 62, id 22995, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.30441 > Y.Y.Y.Y.9998: Flags [F], cksum 0xced9 (correct), seq 4232454280, win 65535, length 0
15:39:35.362371 IP (tos 0x0, ttl 62, id 46525, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.15067 > Y.Y.Y.Y.9998: Flags [F], cksum 0x9d94 (correct), seq 1322466127, win 65535, length 0
15:52:27.833978 IP (tos 0x0, ttl 62, id 30955, offset 0, flags [DF], proto TCP (6), length 40)
    10.16.1.5.21254 > Y.Y.Y.Y.9998: Flags [F], cksum 0x36a1 (correct), seq 3524593365, win 65535, length 0

Where 10.16.1.5 runs 8.3-STABLE

I have a PCAP that I can send privately if needed.

>How-To-Repeat:
Haven't tracked it down yet.
>Fix:
none

>Release-Note:
>Audit-Trail:
State-Changed-From-To: open->closed 
State-Changed-By: sem 
State-Changed-When: Fri Jun 8 15:40:03 UTC 2012 
State-Changed-Why:  
Duplicate to kern/168842 

http://www.freebsd.org/cgi/query-pr.cgi?pr=168843 
>Unformatted:
