router: Fix dhcp infinite lease time (#3913)

The previous setup of many hours would not work, due to some internal dnsmasq issues - lease was set correclty, but dnsmasq was setting the dhcp-renew-time (and rebind time) to less than 2 years from the date the lease was issued.

Using "infinite" as the value (instead of the number) works as expected - and (atm) the renew date is set to year 2088, etc.

Co-authored-by: dahn <daan.hoogland@gmail.com>

Author: andrijapanicsb

systemvm/debian/opt/cloud/bin/cs/CsDhcp.py

@@ -174,21 +174,18 @@ def write_hosts(self):
 
     def add(self, entry):
         self.add_host(entry['ipv4_address'], entry['host_name'])
-        # Lease time set to effectively infinite (36000+ days) since we properly control all DHCP/DNS config via CloudStack.
+        # Lease time set to "infinite" since we properly control all DHCP/DNS config via CloudStack.
         # Infinite time helps avoid some edge cases which could cause DHCPNAK being sent to VMs since
         # (RHEL) system lose routes when they receive DHCPNAK.
         # When VM is expunged, its active lease and DHCP/DNS config is properly removed from related files in VR,
         # so the infinite duration of lease does not cause any issues or garbage.
-        # There will be soon a PR which also regenerates the /var/lib/misc/dnsmasq.leases (active lease DB file)
-        # in the new VR (when restarting network with cleanup), which will help around RHEL edge cases (described above)
-        # for the VMs who are already running in productions systems with 30d lease time.
-        lease = randint(870000, 870010)
+        lease = 'infinite'
 
         if entry['default_entry']:
-            self.cloud.add("%s,%s,%s,%sh" % (entry['mac_address'],
-                                             entry['ipv4_address'],
-                                             entry['host_name'],
-                                             lease))
+            self.cloud.add("%s,%s,%s,%s" % (entry['mac_address'],
+                                            entry['ipv4_address'],
+                                            entry['host_name'],
+                                            lease))
         else:
             tag = entry['ipv4_address'].replace(".", "_")
             self.cloud.add("%s,set:%s,%s,%s,%sh" % (entry['mac_address'],