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Date: Sat, 11 Aug 2007 01:15:54 GMT
From: Jacek Zapala <jacek@ipv6.jacek.it.pl>
To: freebsd-gnats-submit@FreeBSD.org
Subject: ipv6 pmtu not working
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>Number:         115413
>Category:       kern
>Synopsis:       [ipv6] ipv6 pmtu not working
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-net
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 11 01:20:02 GMT 2007
>Closed-Date:    Fri Aug 24 08:35:33 GMT 2007
>Last-Modified:  Fri Aug 24 08:35:33 GMT 2007
>Originator:     Jacek Zapala
>Release:        6.2
>Organization:
>Environment:
FreeBSD xxxxx 6.2-RELEASE FreeBSD 6.2-RELEASE #0: Wed Apr 25 13:06:39 CEST 2007     root@xxxxxx:/usr/src/sys/i386/compile/DELL_2950  i386
>Description:
IPv6 path MTU discovery does not work. ICMP6 "packet too big" messages
arrive, but seem to be ignored (tcp segment with unmodified mtu is
retransmitted). Instead, tcp "discarded for bad checksums" counter gets
incremented (could be a coincidence?)

Checksum for incoming ICMPv6 packet is ok (according to wireshark),
checksum of tcp packet included in ICMPv6 message is of course wrong
(as not whole original packet fits into 1280 bytes long ICMPv6 message).

Interface:
bce0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=3b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU>

Destination address is normal, unicast address (problem was noticed
when sendmail could not send mail to some destinations).

Reboot didn't help ;-)
As a workaround I have set 1280 bytes mtu for default ipv6 route.

>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-bugs->freebsd-net 
Responsible-Changed-By: linimon 
Responsible-Changed-When: Sat Aug 11 07:31:46 UTC 2007 
Responsible-Changed-Why:  
Over to maintainer(s). 

http://www.freebsd.org/cgi/query-pr.cgi?pr=115413 

From: Jacek Zapala <jacek@ipv6.jacek.it.pl>
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/115413: [ipv6] ipv6 pmtu not working
Date: Mon, 20 Aug 2007 23:24:06 +0200

 Described problem shows only with pf enabled.
 Of course icmpv6 packet too big is not rejected by filter rules:
 # pfctl -s rules | fgrep big
 No ALTQ support in kernel
 ALTQ related functions disabled
 pass in quick on bce0 inet6 proto ipv6-icmp from any to
 2001:xxxx:yyyy::200 icmp6-type toobig
 
 
 

From: Jacek Zapala <jacek@ipv6.jacek.it.pl>
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: kern/115413: [ipv6] ipv6 pmtu not working
Date: Tue, 21 Aug 2007 12:05:18 +0200

 Further debugging:
 
 scp from src_addr to dst_addr which pf debug enabled shows
 
 pf: BAD ICMP 2:0 some_router -> src_addr
 state: TCP src_addr[50400] src_addr[50400]
 dst_addr[22] [lo=2463013638 high=2463020758 win=32844
 modulator=0 wscale=1] [lo=2412460872 high=2412526560 win=1278 modulator=0
 wscale=3] 4:4 seq=2463010534
 
 State table:
 self tcp src_addr[50400] -> dst_addr[22]   ESTABLISHED:ESTABLISHED
 
 
 
State-Changed-From-To: open->closed 
State-Changed-By: dhartmei 
State-Changed-When: Fri Aug 24 08:32:46 UTC 2007 
State-Changed-Why:  
problem was with pf (more details in http://marc.info/?t=118681762200001) 
now fixed (pf.c 1.46, 1.34.2.6) 

http://www.freebsd.org/cgi/query-pr.cgi?pr=115413 
>Unformatted:
