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Dear lvs-users
We use LVS extensively with Keepalived for running redundant
load balanced setups. As part of the load balancer we sometimes
use what is called a sorry_server in Keepalived. This maps to a
local real server in LVS speak.
In recent versions we have found a change in behaviour that
seems to break that functionality of a local sorry_server. It boils
down to LVS not setting the forward mode to "Local" for addresses for
which there interfaces on the local node.
See the following examples. First on a Ubuntu 10.04.4 LTS:
# uname -a
Linux ubuntuserver1004 2.6.32-54-server #116-Ubuntu SMP Tue Nov 12 19:37:57 UTC
2013 x86_64 GNU/Linux
# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.10.0.2:80 wlc
-> 127.0.0.1:80 Local 1 0 0
In this example the forward mode is correctly set to "Local". In newer
versions this doesn't seem to work any more:
# uname -a
Linux ubuntuserver1204 3.8.0-34-generic #49~precise1-Ubuntu SMP Wed Nov 13
18:05:00 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
# ipvsadm -A -t 10.10.0.2:80
# ipvsadm -a -t 10.10.0.2:80 -r 127.0.0.1
# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 10.10.0.2:80 wlc
-> 127.0.0.1:80 Route 1 0 0
Note that in this later cate the forward mode in the second example
has *NOT* been set to "Local".
This behaviour contradicts the documentation in the manual, which states:
> Regardless of the packet-forwarding mechanism specified, real servers for
> addresses for which there are interfaces on the local node will be use
> the local forwarding method, then packets for the servers will be passed to
> upper layer on the local node. This cannot be specified by ipvsadm, rather
> it set by the kernel
> as real servers are added or modified.
Is the observed behaviour desired or a bug in LVS or even the Kernel?
Regards
Matías
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