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Not seeing multicast on veth [message #37736] Thu, 15 October 2009 09:27 Go to previous message
zajdee is currently offline  zajdee
Messages: 2
Registered: October 2009
Junior Member
Hello,

I have a problem with multicast not coming 'out' of the virtual machine.

I am trying to set up a test environment of a three virtual machines on a single OpenVZ master host. I have quite some experience with OpenVZ, however haven't found a single working solution for the problem I am seeing now.

The environment is as follows:
- virtual machines with Debian Lenny Linux, two veth interfaces
- master host with Debian Lenny Linux, two VLANs, each VLAN bridged to one of the veth interfaces of a virtual machine

The virtual machines run the Linux VRRP userspace daemon, ucarp, which uses multicast to communicate with other VMs.

And finally, the problem is, that I cannot see the multicast traffic coming out of the VM, if I run tcpdump -i veth101.84 on master (101 is the VM's ID)
I can, however, see the traffic, if I run tcpdump inside the VM (tcpdump -i eth0.84).

The Linux kernel is 2.6.18-openvz el5.028stab064.7.szn5, based on RHEL's kernel el5.028stab064.7 with some specific addons for our environment.

I know that there has been an issue in the el5.028stab033 RHEL kernel, however that issue (according to various forums) has been resolved in stab034.

Does anyone has any idea, what could be the problem of not seeing the multicasts on veth?

Thanks in advance.

And now some details from the master:
$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.2.12.0       0.0.0.0         255.255.255.0   U     0      0        0 eth0.12
192.168.0.0     10.2.12.1       255.255.0.0     UG    0      0        0 eth0.12
172.16.0.0      10.2.12.1       255.240.0.0     UG    0      0        0 eth0.12
10.0.0.0        10.2.12.1       255.0.0.0       UG    0      0        0 eth0.12
0.0.0.0         10.2.12.1       0.0.0.0         UG    0      0        0 eth0.12

$ brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.00238b89da94       no              eth0
br0.131         8000.0018511abf2b       no              eth0.131
                                                        veth101.131
                                                        veth102.131
                                                        veth103.131
br0.84          8000.0018511abf2b       no              eth0.84
                                                        veth101.84
                                                        veth102.84
                                                        veth103.84

$ tcpdump -i veth101.84 '(vrrp)' -n
tcpdump: WARNING: veth101.84: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on veth101.84, link-type EN10MB (Ethernet), capture size 96 bytes
11:23:05.927984 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:06.875967 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:06.876338 IP 10.2.84.62 > 224.0.0.18: VRRPv2, Advertisement, vrid 62, prio 0, authtype none, intvl 5s, length 36
11:23:06.876360 IP 10.2.84.63 > 224.0.0.18: VRRPv2, Advertisement, vrid 63, prio 0, authtype none, intvl 5s, length 36
11:23:06.876382 IP 10.2.84.61 > 224.0.0.18: VRRPv2, Advertisement, vrid 61, prio 0, authtype none, intvl 5s, length 36
11:23:07.799989 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:08.748021 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:09.687968 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:10.679980 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20


and also from the VM, the tcpdump was captured at the same time:
$ tcpdump -i eth0.84 '(vrrp)' -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0.84, link-type EN10MB (Ethernet), capture size 96 bytes
11:23:06.875967 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:06.876338 IP 10.2.84.62 > 224.0.0.18: VRRPv2, Advertisement, vrid 62, prio 0, authtype none, intvl 5s, length 36
11:23:06.876360 IP 10.2.84.63 > 224.0.0.18: VRRPv2, Advertisement, vrid 63, prio 0, authtype none, intvl 5s, length 36
11:23:06.876382 IP 10.2.84.61 > 224.0.0.18: VRRPv2, Advertisement, vrid 61, prio 0, authtype none, intvl 5s, length 36
11:23:07.799989 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:07.800050 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 136, prio 0, authtype none, intvl 1s, length 36
11:23:07.800053 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 138, prio 196, authtype none, intvl 1s, length 36
11:23:07.800057 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 137, prio 128, authtype none, intvl 1s, length 36
11:23:08.748021 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:09.687968 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:09.688028 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 138, prio 196, authtype none, intvl 1s, length 36
11:23:09.688030 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 137, prio 128, authtype none, intvl 1s, length 36
11:23:09.688032 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 136, prio 0, authtype none, intvl 1s, length 36
11:23:10.679980 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:11.551986 IP 10.2.84.240 > 224.0.0.18: VRRPv2, Advertisement, vrid 84, prio 120, authtype none, intvl 1s, length 20
11:23:11.552036 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 136, prio 0, authtype none, intvl 1s, length 36
11:23:11.552041 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 138, prio 196, authtype none, intvl 1s, length 36
11:23:11.552046 IP 10.2.84.136 > 224.0.0.18: VRRPv2, Advertisement, vrid 137, prio 128, authtype none, intvl 1s, length 36

$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
3: venet0: <BROADCAST,POINTOPOINT,NOARP> mtu 1500 qdisc noop state DOWN
    link/void
5: eth0.84: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether 00:18:51:ba:74:18 brd ff:ff:ff:ff:ff:ff
    inet 10.2.84.136/24 brd 10.2.84.255 scope global eth0.84
    inet6 fe80::218:51ff:feba:7418/64 scope link
       valid_lft forever preferred_lft forever
7: eth0.131: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether 00:18:51:2d:bd:bf brd ff:ff:ff:ff:ff:ff
    inet xx.xx.xx.136/24 brd xx.xx.xx.255 scope global eth0.131
    inet xx.xx.xx.138/24 scope global secondary eth0.131
    inet xx.xx.xx.137/24 scope global secondary eth0.131
    inet6 fe80::218:51ff:fe2d:bdbf/64 scope link
       valid_lft forever preferred_lft forever

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.2.84.0       0.0.0.0         255.255.255.0   U     0      0        0 eth0.84
xx.xx.xx.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0.131
192.168.0.0     10.2.84.1       255.255.0.0     UG    0      0        0 eth0.84
172.16.0.0      10.2.84.1       255.240.0.0     UG    0      0        0 eth0.84
10.0.0.0        10.2.84.1       255.0.0.0       UG    0      0        0 eth0.84
0.0.0.0         xx.xx.xx.1      0.0.0.0         UG    0      0        0 eth0.131
 
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