VLAN trunking and fragmentation

[Pyun YongHyeon]

On Wed, Mar 12, 2008 at 10:22:34PM +0100, Giulio Ferro wrote:
 > Sam Leffler wrote:
 > >You failed to provide the output of ifconfig on your running system.  
 > >Be sure any checksum offload is disabled (should be by the bridge).
 > >
 > >    Sam
 > My bad.
 > 
 > I switched off checksum offload in /etc/rc.conf like this:
 > ifconfig_re0="inet 192.168.60.1 netmask 255.255.255.0 -rxcsum -txcsum"
 > (same thing on the other machine)
 > 
 > Now my ifconfig on PC #1 is :
 > -----------------------------------------
 > # ifconfig re0
 > re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
 >        options=98<VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
 >        ether 00:14:c1:40:c2:e8
 >        inet 192.168.60.1 netmask 0xffffff00 broadcast 192.168.60.255
 >        media: Ethernet autoselect (1000baseTX <full-duplex>)
 >        status: active
 > 
 > # ifconfig vlan0
 > vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
 >        ether 00:14:c1:40:c2:e8
 >        inet 192.168.100.1 netmask 0xffffff00 broadcast 192.168.100.255
 >        media: Ethernet autoselect (1000baseTX <full-duplex>)
 >        status: active
 >        vlan: 10 parent interface: re0
 > -----------------------------------------
 > 
 > on PC #2 :
 > -----------------------------------------
 > # ifconfig re0
 > re0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
 >        options=98<VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
 >        ether 00:15:8a:00:48:80
 >        inet 192.168.60.2 netmask 0xffffff00 broadcast 192.168.60.255
 >        media: Ethernet autoselect (1000baseTX <full-duplex>)
 >        status: active
 > 
 > # ifconfig vlan0
 > vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
 >        ether 00:15:8a:00:48:80
 >        inet 192.168.100.2 netmask 0xffffff00 broadcast 192.168.100.255
 >        media: Ethernet autoselect (1000baseTX <full-duplex>)
 >        status: active
 >        vlan: 10 parent interface: re0
 > -----------------------------------------
 > 
 > 
 > 
 > Any packet greater than 1472 which gets fragmented doesn't pass through:
 > command : ping -c 1 -s 1473 192.168.100.2
 > 
 > on the sending machine:
 > -----------------------------------------
 > # tcpdump -i re0 -n -vvv not tcp and not stp
 > 
 > 23:11:07.649600 IP (tos 0x0, ttl 64, id 399, offset 0, flags [+], proto 
 > ICMP (1), length 1500) 192.168.100.1 > 192.168.100.2: ICMP echo request, 
 > id 19972, seq 0, length 1480
 > 23:11:07.649605 IP (tos 0x0, ttl 64, id 399, offset 1480, flags [none], 
 > proto ICMP (1), length 21) 192.168.100.1 > 192.168.100.2: icmp
 > -----------------------------------------
 > 
 > 
 > Whereas on the receiving machine I don't get any packet.
 > 

To rule out other possible issues, would you try the following
files on your box?

http://people.freebsd.org/~yongari/re/if_re.c
http://people.freebsd.org/~yongari/re/if_rereg.h

-- 
Regards,
Pyun YongHyeon