kern/107523: ng_fec and IPv6 (problem might also affect carp)

Johan Ström johan at stromnet.se
Thu Jan 4 08:30:14 PST 2007


>Number:         107523
>Category:       kern
>Synopsis:       ng_fec and IPv6 (problem might also affect carp)
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jan 04 16:30:13 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Johan Ström
>Release:        6.1-RELEASE-p11
>Organization:
Stromnet
>Environment:
FreeBSD gw-2.stromnet.se 6.1-RELEASE-p11 FreeBSD 6.1-RELEASE-p11 #5: Sat Dec 23 00:16:35 CET 2006     johan at elfi.stromnet.se:/usr/obj/usr/src/sys/ROUTER.POLLING  i386

>Description:
I'am using ng_fec with VLAN support (kern/102540).
On one box, gw-2, I has fec0 consisting of hme0-4, and on top of fec0 I have vlan10 and a few more.

When one of my boxes on VLAN 10 starts and tries to use IPv6 through this box (gw-2, IPv4/6 router), it has problems finding it.

tcpdumping on the other box it seems its sending neighbour solicitations for gw-2s address. Hower, tcpdumping on gw-2's vlan10 does not reveal any neighbour solicitations at all.. dumping on fec0 doesnt show anything either..
However, if i start dumping on hme0 (which also means putting hme0 into promisc mode), I see the packets and in an instant gw-2 responds with a neighbour advertisement and the other box can now start to talk with gw-2.
Reproduced it today, the other box had been restarted, and it failed to talk IPv6 with gw-2. Did an ifconfig hme0 promisc and immediatly traffic started flowing.

So, it seems fec doesnt tell the interfaces below to accept some special traffic (these solicitations, are they multicast? im not sure..)

I have tried to run carp ontop of the vlan interfaces too, without much luck.. Or some strange luck, it worked then i rebooted the box and i didnt get it to work again.. However I never tested if promisc'ing the interface helped, but it might very well do (i had used tcpdump alot before i rebooted it so that might have been why it worked).

So, ng_fec doesnt seem to tell the underlying interface what to listen for properly or something?


>How-To-Repeat:
Use ng_fec with a vlan interface (not sure this is required though, havent tried directly on ng_fec)
Setup an IPv6 address on the vlan (or fec?) interface
Try to ping6 the IPv6 address from another box
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:


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