Working with qeth devices

Red Hat Enterprise Linux 8.6 LPAR mode z/VM guest

Typical tasks that you need to perform when working with qeth devices include creating group devices, finding out the type of a network adapter, and setting a device online or offline.

About this task

Most of these tasks involve writing to and reading from attributes of qeth group devices in sysfs. This is useful on a running system where you want to make dynamic changes. If you want to make the changes persistent across IPLs, use the interface configuration files. Network configuration parameters are defined in /etc/sysconfig/network-scripts/ifcfg-<if_name>. An example of how to define a qeth device persistently is in the installation documentation on the Red Hat website. For a general discussion of network configuration files, see configuration documentation on the Red Hat documentation website
https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux

Table 1 and Table 3 serve as both a task overview and a summary of the attributes and the possible values you can write to them. Underlined values are defaults.

Tip: Use the chzdev command to configure devices instead of using the attributes directly. You can also use the znetconf command for network devices.

Not all attributes are applicable to each device. Some attributes apply only to HiperSockets or only to OSA-Express CHPIDs in QDIO mode, other attributes are applicable to IPv4 interfaces only. See the task descriptions for the applicability of each attribute.

Table 1. qeth tasks and attributes common to layer2 and layer3
Task	Corresponding attributes	Possible attribute values
Creating a qeth group device	group	n/a
Removing a qeth group device	ungroup	0 or 1
Setting the layer2 attribute	layer2	0 or 1, see Layer 2 and layer 3¹
Using priority queueing	priority_queueing	prio_queueing_vlan prio_queueing_skb prio_queueing_prec prio_queueing_tos no_prio_queueing no_prio_queueing:0 no_prio_queueing:1 no_prio_queueing:2 no_prio_queueing:3
Specifying the number of inbound buffers	buffer_count	integer in the range 8 - 128. The default is 64 for OSA devices and 128 for HiperSockets devices
Specifying the relative port number	portno	integer, either 0 or 1, the default is 0
Finding out the type of your network adapter	card_type	n/a, read-only
Setting a device online or offline	online	0 or 1
Finding out the interface name of a qeth group device	if_name	n/a, read-only
Finding out the bus ID of a qeth interface	none	n/a
Activating an interface	none	n/a
Deactivating an interface	none	n/a
Recovering a device	recover	1
Enabling and disabling TCP segmentation offload	none	n/a
Configuring the receive checksum offload feature	none	n/a
Configuring the transmit checksum offload feature	none	n/a
Isolating data connections	isolation	none, drop, forward
Displaying and resetting QETH performance statistics	performance_stats	0 or 1
Capturing a hardware trace	hw_trap	arm disarm
¹A value of -1 means that the layer has not been set and that the default layer setting is used when the device is set online.

Table 2. qeth functions and attributes in layer 2 mode
Function	Corresponding attributes	Possible attribute values
Configuring a network device as a member of a Linux bridge	bridge_role bridge_state bridge_hostnotify	primary, secondary, none active, standby, inactive 0 or 1
Advanced packet-handling configuration	vnicc/bridge_invisible vnicc/flooding vnicc/learning vnicc/mcast_flooding vnicc/rx_bcast vnicc/takeover_learning vnicc/takeover_setvmac vnicc/learning_timeout	0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 integer in the range 60 - 86400 the default is 600

Table 3. qeth tasks and attributes in layer 3 mode
Task	Corresponding attributes	Possible attribute values
Setting up a Linux router in layer 3	route4 route6	primary_router secondary_router primary_connector secondary_connector multicast_router no_router
Faking broadcast capability	fake_broadcast ¹	0 or 1
Taking over IP addresses	ipa_takeover/enable	0 or 1 or toggle
	ipa_takeover/add4 ipa_takeover/add6 ipa_takeover/del4 ipa_takeover/del6	IPv4 or IPv6 IP address and mask bits
	ipa_takeover/invert4 ipa_takeover/invert6	0 or 1 or toggle
Configuring a device for proxy ARP	rxip/add4 rxip/del4	IPv4 IP address
Configuring a device for NDP proxy	rxip/add6 rxip/del6	IPv6 IP address
Configuring a device for virtual IP address (VIPA)	vipa/add4 vipa/add6 vipa/del4 vipa/del6	IPv4 or IPv6 IP address
Configuring a HiperSockets device for AF_IUCV addressing	hsuid	1 to 8 characters
Setting up a HiperSockets network traffic analyzer	sniffer	0 or 1
¹ not valid for HiperSockets

Tip: Use the qethconf command instead of using the attributes for IPA, proxy ARP, and VIPA directly (see qethconf - Configure qeth devices).

sysfs provides multiple paths through which you can access the qeth group device attributes. For example, if a device with bus ID 0.0.a100 corresponds to interface enca100:

/sys/bus/ccwgroup/drivers/qeth/0.0.a100
/sys/bus/ccwgroup/devices/0.0.a100
/sys/devices/qeth/0.0.a100
/sys/class/net/enca100/device

all lead to the attributes for the same device. For example, the following commands are all equivalent and return the same value:

# cat /sys/bus/ccwgroup/drivers/qeth/0.0.a100/if_name
enca100
# cat /sys/bus/ccwgroup/devices/0.0.a100/if_name
enca100
# cat /sys/devices/qeth/0.0.a100/if_name
enca100
# cat /sys/class/net/enca100/device/if_name
enca100

The path through /sys/class/net becomes available when the device is first set online and the interface is created. The path persists until the device is ungrouped. Furthermore, it might lead to a different device if the assignment of interface names changes. A change can occur after rebooting or when devices are ungrouped and new group devices created.

Tip: Work through one of the paths that are based on the device bus-ID.

The following sections describe the tasks in detail.