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SubjectBonding Driver Questions
Hi, I'd like to use channel bonding driver for high availability.

Currenly the bonding driver does not detect a dead slave link. When a
slave link dies, it causes lots of network retransmits and the effective
speed of the bonding device drops to almost zero. This has been verified
in the lab.

How difficult would it be to "teach" the bonding driver to check for the
link status of its slave interfaces? Does ethernet layer provides a
uniform way to check for the link status or it is adapter dependent?

If such extension cannot be added to the kernel for whatever reason in
the near future, can it be done from user space? It seems a user space
approach would require two things:

1) a user space program to check for link status
2) a way to unbind a slave device without bringing the master device
down. Currently the slave interface cannot be brought down without
bringing down the master interface. I.e today, if I have
bond0=eth0+eth1, and the link on eth1 goes down, I have to do

(a) ifconfig bond0 down
(b) ifconfig eth0 down
(c) ifconfig eth1 down
(d) ifconfig bond0 $IP up
(e) ifenslave bond0 eth0

At stage (a) the routing is broken, which is a problem. (I guess a dummy
device with the same network as bond0 could be added before (a) and
deleted after (d), but this approach is already ugly enough.) So, here
are two questions:

1) How can I check for the link status from the user space?
2) Could enslaved interface be released without bringing the master
interface down? If yes, how? Could we have ifunslave?

Constantine Gavrilov
Unix System Administrator and Programmer
Xpert Integrated Systems
1 Shenkar St, Herzliya 46725, Israel
Phone: (972-8)-952-2361
Fax: (972-9)-952-2366
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