On Mon, Apr 21, 2014 at 12:38 PM, Hui Kang <[email protected]> wrote: > Hi. > I would like to test the function of IP fragmentation and vlan together of > openvswitch. I found that the OVS switch on the receiver side can not > receive > the fragmented IP correctly. Below is my testbed setup. > > On the sender side (a VM), I run iperf with fragmentation and without > fragmentation by > > iperf -c receiver's IP -u -l 2000 ---- has fragmentation > iperf -c receiver's IP -u ---- no fragmentation > > On the receiver VM's host machine (where the OVS switch runs), I use tcpdump > to > capture the data. I found that I can see all the IP packets with the no > fragmentation Iperf correctly, like > > 15:26:34.507647 52:54:00:5d:98:5a > 52:54:00:37:a7:d6, ethertype > 802.1Q (0x8100), length 1516: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl > 64, id 48308, offset 0, flags [DF], proto UDP (17), length 1498) > 192.168.10.44.51218 > 192.168.10.61.5001: [udp sum > ok] UDP, length 1470 > 15:26:34.758064 52:54:00:5d:98:5a > 52:54:00:37:a7:d6, ethertype > 802.1Q (0x8100), length 1516: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl > 64, id 48309, offset 0, flags [DF], proto UDP (17), length 1498) > 192.168.10.44.51218 > 192.168.10.61.5001: [udp sum > ok] UDP, length 1470 > > However, when I use the iperf command with fragmentation, the VM can not > receive > the UDP packet and the tcpdump on the host shows > > 15:32:18.598578 52:54:00:5d:98:5a > 52:54:00:37:a7:d6, ethertype > 802.1Q (0x8100), length 70: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl 64, > id 41493, offset 1976, flags [none], proto UDP (17), length 52) > 192.168.10.44 > 192.168.10.61: udp > 15:32:18.629009 52:54:00:5d:98:5a > 52:54:00:37:a7:d6, ethertype > 802.1Q (0x8100), length 70: vlan 100, p 0, ethertype IPv4, (tos 0x0, ttl 64, > id 41495, offset 1976, flags [none], proto UDP (17), length 52) > 192.168.10.44 > 192.168.10.61: udp > As you can see, all captureed packets have the offset as 1976. So the first > fragment of the IP packets are very likely being dropped. I also use > ovs-ofctl get-frags br to see the fragmentation handling mode is "normal". > > Is there anything wrong regarding my setup or any bug in OVS? Thanks.
Is your MTU set correctly on all links? 1976 is larger than the default Ethernet MTU. OVS doesn't do much with fragmentation (it's the endpoint), so it seems unlikely be a bug there. _______________________________________________ discuss mailing list [email protected] http://openvswitch.org/mailman/listinfo/discuss
