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Date:      Mon, 29 Oct 2001 12:40:27 +0000
From:      Mike Bristow <michaelb@thus.net>
To:        FreeBSD-gnats-submit@freebsd.org
Subject:   kern/31586: netgraph bridges cause connectivity probs from bridge
Message-ID:  <E15yBiN-0000cK-00@singsing.eng.demon.net>

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>Number:         31586
>Category:       kern
>Synopsis:       netgraph bridges cause connectivity probs from bridge
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Oct 29 04:50:03 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Mike Bristow
>Release:        FreeBSD 4.4-STABLE-20011027T210032 i386
>Organization:
THUS PLC
>Environment:
System: FreeBSD singsing 4.4-STABLE-20011027T210032 FreeBSD 4.4-STABLE-20011027T210032 #0: Sat Oct 27 22:33:54 BST 2001 michaelb@singsing:/usr/obj/usr/src/sys/SINGSING-ENG i386

>Description:

Using a suitibly modified copy of
/usr/share/examples/netgraph/ether.bridge, I brought up a bridge
between de0, de1, de2, and xl0 (with xl0 being the "local interface".

The topology is :

   [ singsing ] <-x de0 -> [ win2k box]
                <-x de1 -> [ solaris box ]
                <-x de2 -> [ utterly borked freebsd-current box ]
	        <-- xl0 -> [ summit 48 + rest of network, default route etc ]

where <-x interface -> indicates a crossover cat5 cable, and <--
interface -> indicates a normal bit of cat5

[ this is all done because of a lack of wall ports in the office ]

Machines attached to the de0, de1 or de2 have connectivity problems
from singsing, but they are reachable from other machines on the network.

A "snoop -o snoop.out host singsing and host solaris_box" run on
the solaris box while simultanously running "telnet singsing imap"
in another windown suggest that the TCP checksum is wrong (acording to 
ethereal).  I haven't "snooped" icmp echo requests/responses in
either direction yet; nor did I run tcpdump on "singsing".

Traffic out of the xl0 interface appears to be unaffected.

http://www.urgle.com/~mike/netgraph/ has my modified ether.bridge;
the snoop output as seen by the solaris box; and dmesg output from "singsing".

This problem has appeared between 4.4-STABLE-20011001T111411 &
4.4-STABLE-20011027T210032

(where the timestamp is the time "cvs update" was run against a local
CVS mirror that cvsups hourly)

If additional snoops/tcpdumps on assorted hosts would be useful,
or if anything else would help track this down, let me know.

>How-To-Repeat:

	Set up a bridge using /usr/share/examples/netgraph/ether.bridge
and a LOCAL_IFACE; try and connect from the bridge to machines that
are attached to BRIDGE_IFACES but not LOCAL_IFACE

>Fix:

	An evil workaround is:
	for i in machines attached to de{0,1,2} ; do 
		route add $i $default_route
	done

but this is obviously less than ideal.
>Release-Note:
>Audit-Trail:
>Unformatted:

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