[Bug 785668] [NEW] bonding inside a bridge does not update ARP correctly when bridged net accessed from within a VM

[Louis Bouchard]

Public bug reported:

Binary package hint: qemu-kvm

Description: Ubuntu 10.4.2
Release: 10.04


When setting a KVM host with a bond0 interface made of eth0 and eth1 and using this bond0 interface for a bridge to KVM VMs, the ARP tables do not get updated correctly and

Reproducible: 100%, with any of the load balancing mode

How to reproduce the problem

- Prerequisites:
1 One KVM system with 10.04.02 server,  configured as a virtual host is needed. The following /etc/network/interfaces was used for the test :

# grep  -v ^# /etc/network/interfaces
auto lo
iface lo inet loopback


auto bond0
iface bond0 inet manual
	post-up ifconfig $IFACE up
	pre-down ifconfig $IFACE down
	bond-slaves none
	bond_mode balance-rr
	bond-downdelay 250
	bond-updelay 120
auto eth0
allow-bond0 eth0
iface eth0 inet manual
	bond-master bond0
auto eth1
allow-bond0 eth1
iface eth1 inet manual
	bond-master bond0

auto br0
iface br0 inet dhcp
	# dns-* options are implemented by the resolvconf package, if installed
	bridge-ports bond0
	bridge-stp off
	bridge-fd 9
	bridge-hello 2
	bridge-maxage 12
	bridge_max_wait 0

One VM running Maverick 10.10 server, standard installation, using the
following /etc/network/interfaces file :

grep -v ^# /etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
        address 10.153.107.92
        netmask 255.255.255.0
        network 10.153.107.0
        broadcast 10.153.107.255

--------------
On a remote bridged network system :
$ arp -an
? (10.153.107.188) à 00:1c:c4:6a:c0:dc [ether] sur tap0
? (16.1.1.1) à 00:17:33:e9:ee:3c [ether] sur wlan0
? (10.153.107.52) à 00:1c:c4:6a:c0:de [ether] sur tap0

On KVMhost
$ arp -an
? (10.153.107.80) at ee:99:73:68:f0:a5 [ether] on br0

On VM
$ arp -an
? (10.153.107.61) at <incomplete> on eth0

1) Test #1 : ping from VM (10.153.107.92) to remote bridged network
system (10.153.107.80) :

- On remote bridged network system :
caribou at marvin:~$ arp -an
? (10.153.107.188) à 00:1c:c4:6a:c0:dc [ether] sur tap0
? (16.1.1.1) à 00:17:33:e9:ee:3c [ether] sur wlan0
? (10.153.107.52) à 00:1c:c4:6a:c0:de [ether] sur tap0

- On KVMhost
ubuntu at VMhost:~$ arp -an
? (10.153.107.80) at ee:99:73:68:f0:a5 [ether] on br0

- On VM
ubuntu at vm1:~$ ping 10.153.107.80
PING 10.153.107.80 (10.153.107.80) 56(84) bytes of data.
>From 10.153.107.92 icmp_seq=1 Destination Host Unreachable
>From 10.153.107.92 icmp_seq=2 Destination Host Unreachable
>From 10.153.107.92 icmp_seq=3 Destination Host Unreachable
^C
--- 10.153.107.80 ping statistics ---
4 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3010ms
pipe 3
ubuntu at vm1:~$ arp -an
? (10.153.107.61) at <incomplete> on eth0
? (10.153.107.80) at <incomplete> on eth0

2) Test #2 : ping from remote bridged network system (10.153.107.80) to
VM (10.153.107.92) :

- On remote bridged network system :
$ ping 10.153.107.92
PING 10.153.107.92 (10.153.107.92) 56(84) bytes of data.
64 bytes from 10.153.107.92: icmp_req=1 ttl=64 time=327 ms
64 bytes from 10.153.107.92: icmp_req=2 ttl=64 time=158 ms
64 bytes from 10.153.107.92: icmp_req=3 ttl=64 time=157 ms
^C
--- 10.153.107.92 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 157.289/214.500/327.396/79.831 ms
caribou at marvin:~$ arp -an
? (10.153.107.188) à 00:1c:c4:6a:c0:dc [ether] sur tap0
? (16.1.1.1) à 00:17:33:e9:ee:3c [ether] sur wlan0
? (10.153.107.52) à 00:1c:c4:6a:c0:de [ether] sur tap0
? (10.153.107.92) à 52:54:00:8c:e0:3c [ether] sur tap0

- On KVMhost
$ arp -an
? (10.153.107.80) at ee:99:73:68:f0:a5 [ether] on br0

- On VM
arp -an
? (10.153.107.61) at <incomplete> on eth0
? (10.153.107.80) at ee:99:73:68:f0:a5 [ether] on eth0


3) Test #3 : New ping from VM (10.153.107.92) to remote bridged network system (10.153.107.80) :
- On remote bridged network system :
$ arp -an
? (10.153.107.188) à 00:1c:c4:6a:c0:dc [ether] sur tap0
? (16.1.1.1) à 00:17:33:e9:ee:3c [ether] sur wlan0
? (10.153.107.52) à 00:1c:c4:6a:c0:de [ether] sur tap0
? (10.153.107.92) à 52:54:00:8c:e0:3c [ether] sur tap0

- On KVMhost
ubuntu at VMhost:~$ arp -an
? (10.153.107.80) at ee:99:73:68:f0:a5 [ether] on br0

- On VM
ubuntu at vm1:~$ ping 10.153.107.80
PING 10.153.107.80 (10.153.107.80) 56(84) bytes of data.
64 bytes from 10.153.107.80: icmp_req=1 ttl=64 time=154 ms
64 bytes from 10.153.107.80: icmp_req=2 ttl=64 time=170 ms
64 bytes from 10.153.107.80: icmp_req=3 ttl=64 time=154 ms
^C
--- 10.153.107.80 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 154.072/159.465/170.058/7.504 ms

tcpdump traces are available for those tests. Test system is available
upon request.

Workaround:

Use the bonded device in "active-backup" mode

ProblemType: Bug
DistroRelease: Ubuntu 10.04.02
Package: qemu-kvm-0.12.3+noroms-0ubuntu9.6
Uname: Linux 2.6.35-25-serverr x86_64
Architecture: amd64

** Affects: qemu-kvm (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/785668

Title:
  bonding inside a bridge does not update ARP correctly when bridged net
  accessed from within a VM