On 8/17/2018 2:56 AM, Harald Hoyer wrote:
On 17.08.2018 11:51, Harald Hoyer wrote:
On 16.08.2018 00:17, Siwei Liu wrote:
On Wed, Aug 15, 2018 at 12:05 PM, Samudrala, Sridhar
<sridhar.samudrala@xxxxxxxxx> wrote:
On 8/14/2018 5:03 PM, Siwei Liu wrote:
Are we sure all userspace apps skip and ignore slave interfaces by
just looking at "IFLA_MASTER" attribute?
When STANDBY is enabled on virtio-net, a failover master interface
will appear, which automatically enslaves the virtio device. But it is
found out that iSCSI (or any network boot) cannot boot strap over the
new failover interface together with a standby virtio (without any VF
or PT device in place).
Dracut (initramfs) ends up with timeout and dropping into emergency shell:
[ 228.170425] dracut-initqueue[377]: Warning: dracut-initqueue
timeout - starting timeout scripts
[ 228.171788] dracut-initqueue[377]: Warning: Could not boot.
Starting Dracut Emergency Shell...
Generating "/run/initramfs/rdsosreport.txt"
Entering emergency mode. Exit the shell to continue.
Type "journalctl" to view system logs.
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or
/boot
after mounting them and attach it to a bug report.
dracut:/# ip l sh
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
state UP mode DEFAULT group default qlen 1000
link/ether 9a:46:22:ae:33:54 brd ff:ff:ff:ff:ff:ff\
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
master eth0 state UP mode DEFAULT group default qlen 1000
link/ether 9a:46:22:ae:33:54 brd ff:ff:ff:ff:ff:ff
dracut:/#
If changing dracut code to ignore eth1 (with IFLA_MASTER attr),
network boot starts to work.
Does dracut by default tries to use all the interfaces that are UP?
Yes. The specific dracut cmdline of our case is "ip=dhcp
netroot=iscsi:... ", but it's not specific to iscsi boot. And because
of same MAC address for failover and standby, while dracut tries to
run DHCP on all interfaces that are up it eventually gets same route
for each interface. Those conflict route entries kill off the network
connection.
The reason is that dracut has its own means to differentiate virtual
interfaces for network boot: it does not look at IFLA_MASTER and
ignores slave interfaces. Instead, users have to provide explicit
option e.g. bond=eth0,eth1 in the boot line, then dracut would know
the config and ignore the slave interfaces.
Isn't it possible to specify the interface that should be used for network
boot?
As I understand it, one can only specify interface name for running
DHCP but not select interface for network boot. We want DHCP to run
on every NIC that is up (excluding the enslaved interfaces), and only
one of them can get a route entry to the network boot server (ie.g.
iSCSI target).
However, with automatic creation of failover interface that assumption
is no longer true. Can we change dracut to ignore all slave interface
by checking IFLA_MASTER? I don't think so. It has a large impact to
existing configs.
What is the issue with checking for IFLA_MASTER? I guess this is used with
team/bonding setups.
That should be discussed within and determined by the dracut
community. But the current dracut code doesn't check IFLA_MASTER for
team or bonding specifically. I guess this change might have broader
impact to existing userspace that might be already relying on the
current behaviour.
Thanks,
-Siwei
Is there a sysfs flag for IFF_SLAVE? Or any "ip" output I can use to detect, that it is a IFF_SLAVE?
Oh, it's the other way around.. dracut should ignore "master" (eth1).
In the above example eth0 is the net_failover device and eth1 is the
lower virtio_net device.
"ip" output of eth1 shows "master eth0". It indicates that eth0 is its
upper/master device.
This information can also be obtained via sysfs too.
/sys/class/net/eth1/upper_eth0
Can the master enslave the "eth0", if it is already "UP" and busy later on?
eth0 is the master/failover device and eth1 gets registered as its slave
via NETDEV_REGISTER event.
dracut should ignore eth1 in this setup.
