Description of problem:
SIP request message with same call-id, but different source IP is routed to different server as if it was newly initiated call-id and connection breaks.

Setup:
=======

SIP clients ------------> keepalived Server ------> Real Server
192.168.100.116 192.168.100.118
192.168.100.121

Version-Release number of selected component (if applicable):
keepalived 1.3.5

How reproducible:
Always by customer

Actual results:
Current Flow:
SIPP(192.168.100.171) — INVITE ---> LB(192.168.100.116) ---> RealServer(192.168.100.118)
SIPP(192.168.100.171) <----- 200 ----- RealServer(192.168.100.118)
SIPP(192.168.100.170) ----- ACK -----> LB(192.168.100.116) ---> RealServer(192.168.100.121)
SIPP(192.168.100.170) ----- BYE -----> LB(192.168.100.116) ---> RealServer(192.168.100.121)

1. ipvsadm -Ln --connection --persistent-conn
   IPVS connection entries
   pro expire state source virtual destination pe name pe_data
   UDP 14:07 UDP 192.168.100.170:0 192.168.100.116:5060 192.168.100.121:5060 sip 1-16760@192.168.100.171
   UDP 14:07 UDP 192.168.100.171:0 192.168.100.116:5060 192.168.100.118:5060 sip 1-16760@192.168.100.171

The call-id is same, but packet from 192.168.100.171 is routed to 192.168.100.118

Expected results:
==================

SIPP(192.168.100.171) — INVITE ---> LB(192.168.100.116) ---> RealServer(192.168.100.118)
SIPP(192.168.100.171) <----- 200 ----- RealServer(192.168.100.118)
SIPP(192.168.100.170) ----- ACK -----> LB(192.168.100.116) ---> RealServer(192.168.100.118) ***
SIPP(192.168.100.170) ----- BYE -----> LB(192.168.100.116) ---> RealServer(192.168.100.118) ***

Additional info:
==================
keepalived configuration used:

virtual_server 192.168.100.116 5060 {

1. virtual_server fd00::7ea1:10:1:1:145 5060 {
   delay_loop 5
   lb_algo rr
   lb_kind DR
   ops
   persistence_timeout 60
   persistence_granularity 0.0.0.0 <----------------- This is not working
   persistence_engine sip
   protocol UDP