[lvs-users] TCP Connection Sync Problems RHEL

[Lloyd Brown]

Hi, all.

I'm currently testing a RHEL 6.5 based LVS Director setup for load
balancing SSH connections.  I've used Debian directors for a number of
years, and they've worked great, but for some reason, the RHEL directors
aren't acting the way I'm expecting.

Basically I'm seeing two things:
- The backup director doesn't seem to be getting the client connection
info synchronized
- The connection info (eg. the output of "ipvsadm -L -c") doesn't show
the connection closing.  Instead it stays in "ESTABLISHED" state until
it times out.

I'm not really sure how to troubleshoot the second issue.  So for now,
I'm focusing on the first, the one about the connection sync problem.  I
did capture the packets between the two directors, using tcpdump, and
when I open the capture file in wireshark, I see "Connection Count: 0".
 When I do a similar capture on my working Debian directors, I see
non-zero connection count, and the details of the specific connections,
in the wireshark analysis.

Any thoughts here?  How do I go about finding the problem here?  Should
I be looking at kernel code? ipvsadm code?

I'm using keepalived to manage this, so I'll include that .conf file
here, as well as example capture files from my working Debian setup, and
the non-working RHEL test setup.  Note that the packet captures also
include the VRRP sync packets, but they can be ignored.

Both directors are basically stock RHEL 6.5, running kernel
2.6.32-431.17.1.el6.x86_64, keepalived-1.2.7, and ipvsadm-1.25.

If anyone can point me in the right direction on how to diagnose this,
I'd appreciate it.

Thanks,

-- 
Lloyd Brown
Systems Administrator
Fulton Supercomputing Lab
Brigham Young University
http://marylou.byu.edu

rhel_testing_logindr_sync_no_connections.pcap
Description: application/vnd.tcpdump.pcap

debian_logindr_production_connectionsync.pcap
Description: application/vnd.tcpdump.pcap

! Configuration File for keepalived

global_defs {
   notification_email {
     OBSCURED_EMAIL
   }
   smtp_server OBSCURED_SMTP_SERVER_IP
   smtp_connect_timeout 30
   router_id logindrtest
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 20
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass OBSCURED_AUTH_PASSWORD
    }
    virtual_ipaddress {
        192.168.25.8
        192.168.25.12
    }
    smtp_alert
    nopreempt
    #debug

    lvs_sync_daemon_interface eth0
}


##virtual_server 192.168.25.8 22 {
#virtual_server fwmark 120 {
#   delay_loop 30
#   lb_algo rr
#   lb_kind DR
#   protocol TCP
#   real_server 192.168.25.9 22 {
#      weight 1
#      MISC_CHECK {
#         misc_path "/usr/local/sbin/sshcheck.pl 192.168.25.9"
#         misc_dynamic
#      }
#   }
#   real_server 192.168.25.10 22 {
#      weight 1
#      MISC_CHECK {
#         misc_path "/usr/local/sbin/sshcheck.pl 192.168.25.10"
#         misc_dynamic
#      }
#   }
#    
#}
#

virtual_server 192.168.25.12 22 {
   delay_loop 30
   lb_algo rr
   lb_kind DR
   protocol TCP
   real_server 192.168.25.11 22 {
      weight 1
      MISC_CHECK {
         misc_path "/usr/local/sbin/sshcheck.pl 192.168.25.11"
         misc_dynamic
      }
   }
}


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