Archive for January, 2012

HP Microserver Remote Management Card

Saturday, January 28th, 2012

I recently acquired the Remote Management card for my HP Microserver, which allows remote KVM & power control, IPMI management and hardware monitoring through temperature & fan sensors.

Note the extra connector on the card in addition to the standard PCI-e x1 connector which matches the dedicated slot on the Microserver motherboard. This presented a bit of a problem as I was using the space for the battery backup module for the RAID controller in the neighbouring slot.

Thankfully the long ribbon cable meant I could route the battery up to the space behind the DVD burner freeing the slot again. Once the card was installed and everything screwed back together I booted straight back into CentOS. Given IPMI is touted as a feature I figured that was the first thing to try so I installed OpenIPMI:

# yum -y install OpenIPMI ipmitool
...
# service ipmi start
Starting ipmi drivers:                                     [  OK  ]
# ipmitool chassis status
Could not open device at /dev/ipmi0 or /dev/ipmi/0 or /dev/ipmidev/0: No such file or directory
Error sending Chassis Status command

Hmm, not good. Looking at dmesg shows the following is output when the IPMI drivers get loaded:

ipmi message handler version 39.2
IPMI System Interface driver.
ipmi_si: Adding SMBIOS-specified kcs state machine
ipmi_si: Adding ACPI-specified smic state machine
ipmi_si: Trying SMBIOS-specified kcs state machine at i/o address 0xca8, slave address 0x20, irq 0
ipmi_si: Interface detection failed
ipmi_si: Trying ACPI-specified smic state machine at mem address 0x0, slave address 0x0, irq 0
Could not set up I/O space
ipmi device interface

From reading the PDF manual it states that the IPMI KCS interface is at 0xCA2 in memory, not 0xCA8 that the kernel is trying to probe. Looking at the output from dmidecode shows where this value is probably coming from:

# dmidecode --type 38
# dmidecode 2.11
SMBIOS 2.6 present.
 
Handle 0x001B, DMI type 38, 18 bytes
IPMI Device Information
	Interface Type: KCS (Keyboard Control Style)
	Specification Version: 1.5
	I2C Slave Address: 0x10
	NV Storage Device: Not Present
	Base Address: 0x0000000000000CA8 (I/O)
	Register Spacing: Successive Byte Boundaries

This suggests a minor bug in the BIOS.

Querying the ipmi_si module with modinfo shows it can be persuaded to use a different I/O address so I created /etc/modprobe.d/ipmi.conf containing the following:

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options ipmi_si type=kcs ports=0xca2

Then bounce the service to reload the modules and try again:

# service ipmi restart
Stopping all ipmi drivers:                                 [  OK  ]
Starting ipmi drivers:                                     [  OK  ]

As of CentOS 6.4, the above won’t work as the ipmi_si module is now compiled into the kernel. Instead, you need to edit /etc/grub.conf and append the following to your kernel parameters:

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ipmi_si.type=kcs ipmi_si.ports=0xca2

Thanks to this post for the info. Instead of bouncing the service you’ll need to reboot, then try again:

# ipmitool chassis status
System Power         : on
Power Overload       : false
Power Interlock      : inactive
Main Power Fault     : false
Power Control Fault  : false
Power Restore Policy : always-off
Last Power Event     : 
Chassis Intrusion    : inactive
Front-Panel Lockout  : inactive
Drive Fault          : false
Cooling/Fan Fault    : false
# ipmitool sdr
Watchdog         | 0x00              | ok
CPU_THEMAL       | 32 degrees C      | ok
NB_THERMAL       | 35 degrees C      | ok
SEL Rate         | 0 messages        | ok
AMBIENT_THERMAL  | 20 degrees C      | ok
EvtLogDisabled   | 0x00              | ok
System Event     | 0x00              | ok
SYS_FAN          | 1000 RPM          | ok
CPU Thermtrip    | 0x00              | ok
Sys Pwr Monitor  | 0x00              | ok

Success! With that sorted, you can now use ipmitool to further configure the management card, although not all of the settings are accessible such as IPv6 network settings so you have to use the BIOS or web interface for some of it.

Overall, I’m fairly happy with the management card. It has decent IPv6 support and the Java KVM client works okay on OS X should I ever need it but I couldn’t coax the separate virtual media client to work, I guess only Windows is supported.

OpenBSD PPPoE and RFC 4638

Friday, January 20th, 2012

I upgraded my Internet connection from ADSL 2+ to FTTC a while ago. I’m with Eclipse as an ISP, but it’s basically the same product as BT Infinity, right down to the Openreach-branded modem, (a Huawei Echolife HG612 to be exact).

With this modem, you need to use a router or some software that can do RFC 2516 PPPoE so I simply kept using OpenBSD on my trusty Soekris net4501 and set up a pppoe(4) interface, job done. However what became apparent is the 133 MHz AMD Elan CPU couldn’t fully utilise the 40 Mb/s bandwidth I now had, at best I could get 16-20 Mb/s with a favourable wind. An upgrade was needed.

Given I’d had around 8 years of flawless service from the net4501, another Soekris board was the way to go. Enter the net6501 with comparatively loads more CPU grunt, RAM and interestingly Gigabit NIC chips; not necessarily for the faster speed, but because they can naturally handle a larger MTU.

The reason for this was that I had read that the Huawei modem and BT FTTC network fully supported RFC 4638, which means you can have an MTU of 1,500 bytes on your PPPoE connection which matches what you’ll have on your internal network. Traditionally a PPPoE connection only allowed 1,492 bytes on account of the overhead of 8 bytes of PPPoE headers in every Ethernet frame payload. Because of this it was almost mandatory to perform MSS clamping on traffic to prevent problems. So having an MTU of 1,500 bytes should avoid the need for any clamping trickery, but means your Ethernet interface needs to cope with an MTU of 1,508 bytes, hence the Gigabit NIC (which can accommodate an MTU of 9,000 bytes with no problems).

One small problem remained, pppoe(4) on OpenBSD 5.0 didn’t support RFC 4638. While I sat down and started to add support I noticed someone had added this to the NetBSD driver already, (which is where the OpenBSD driver originated from), so based on their changes I created a similar patch and with some necessary improvements based on feedback from OpenBSD developers it has now been committed to CVS in time for the 5.1 release.

To make use of the larger MTU is fairly obvious, simply set the MTU explicitly on both the Ethernet and PPPoE interfaces to 8 bytes higher than their default. As an example, my /etc/hostname.em0 now contains:

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mtu 1508 up

And similarly my /etc/hostname.pppoe0 contains:

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inet 0.0.0.0 255.255.255.255 NONE mtu 1500 \
        pppoedev em0 authproto chap \
        authname 'user' authkey 'secret' up
dest 0.0.0.1
!/sbin/route add default -ifp \$if 0.0.0.1

I also added support to tcpdump(8) to display the additional PPPoE tag used to negotiate the larger MTU, so when you bring the interface up, watch for PPP-Max-Payload tags going back and forth during the discovery phase.

With that done the remaining step is to remove any scrub max-mss rules in pf.conf(5) as with any luck they should no longer be required.