Re: [Xen-API] Jumbo frames + bonding not being configured properly on bootup

[Rob Hoes <Rob.Hoes@xxxxxxxxxx>]

Hi Nathan,

Thanks for the report. I think you are absolutely right: this is a bug in xapi.

Coincidentally, I believe I have just fixed this in the master branch last week, in this commit: https://github.com/xapi-project/xen-api/commit/0a5994567a44148b9dc94f7cbd1e192394ffb041.

Cheers,

Rob

On 21 Jun 2013, at 23:42, "Nathan March" <nathan@xxxxxx> wrote:

Hi All,

Appear to have found a bug in XCP where bonded interfaces with jumbo frames (mtu 9000) are not being brought up properly on bootup. The bonded interface is setup with mtu 9000, but the underlying interfaces are left at mtu 1500.

I've got my host configured as such:

eth0 + eth1 = Bonded together with mtu 1500 for internet access
eth2 + eth3 = Bonded together with mtu 9000 for mgmt / storage
Management IP is configured on the underlying eth2+3 bond
Storage IPs are configured on vlan interfaces on top of the eth2+3 bond

This all works awesome immediately after configuration, mgmt traffic leaves the bond untagged and storage traffic works as expected.

On reboot of the host however, both eth2 + eth3 are brought up with only mtu 1500:

eth2      Link encap:Ethernet  HWaddr A0:36:9F:0E:D8:54
         UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1
eth3      Link encap:Ethernet  HWaddr A0:36:9F:0E:D8:56
         UP BROADCAST RUNNING PROMISC MULTICAST  MTU:1500  Metric:1

Even though the management interface has mtu 9000 set:

xapi2     Link encap:Ethernet  HWaddr A0:36:9F:0E:D8:54
         inet addr:10.0.16.13  Bcast:10.0.16.255 Mask:255.255.255.0
         UP BROADCAST RUNNING PROMISC MULTICAST  MTU:9000  Metric:1

This results in network apparently working - icmp works, you can ssh somewhere but as soon as a large burst of traffic happens then the tcp connection stalls as it gets fragmented weirdly. Another host which has never been rebooted since configuration (via xencenter) that it has eth2/eth3 properly set with mtu 9000.

Manually doing an "ifconfig ethX mtu 9000" for eth2 + eth3, followed by an xe-toolstack-restart results in a working host again.

So, pretty sure this is a bug =)

- Nathan

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