router: Use source IP from subnet for snat (#5376)

When snat is configured on a vm in a subnet then the source
ip should be taken from the same subnet rather than from
random other subnet.

Co-authored-by: Rakesh Venkatesh <rakeshv@apache.org>

Author: ravening

systemvm/debian/opt/cloud/bin/configure.py

@@ -1008,7 +1008,7 @@ def processStaticNatRule(self, rule):
 
         # Configure the hairpin snat
         self.fw.append(["nat", "front", "-A POSTROUTING -s %s -d %s -j SNAT -o %s --to-source %s" %
-                        (self.getNetworkByIp(rule['internal_ip']), rule["internal_ip"], self.getDeviceByIp(rule["internal_ip"]), self.getGuestIp())])
+                        (self.getNetworkByIp(rule['internal_ip']), rule["internal_ip"], self.getDeviceByIp(rule["internal_ip"]), self.getGuestIpByIp(rule["internal_ip"]))])
 
 
 class IpTablesExecutor: