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<p class="MsoNormal">Hi, I’m developing a hook that govern which subnet is selected from multiple subnets in a shared network for an incoming DHCP package. My network has several subnets per each service (VLAN), one which has restricted addresses (10.20x.x.x)
and several that have non-restricted addresses (192.168.x.x in my dev env). The hook I have now does this by using lease policies which it reads from external Redis database. The problem I’m encountering is moving devices between subnets after they have once
got a lease. When a device has got a lease from one subnet it is hard to get KEA to provision a lease from another one as it is overwriting the subnet of choice made in subnet4_select hook in the lease4_select hook. This is done in the main process in between
these two hooks as I put my choice in subnet4_select by:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>int subnet4_select(CalloutHandle& handle) {<o:p></o:p></b></p>
<p class="MsoNormal"><b> Subnet4Ptr subnet;<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.getArgument("subnet4", subnet);<o:p></o:p></b></p>
<p class="MsoNormal"><b> …<o:p></o:p></b></p>
<p class="MsoNormal"><b> // set chosen subnet to Subnet4Ptr my_subnet_choice<o:p></o:p></b></p>
<p class="MsoNormal"><b> …<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.setArgument("subnet4", my_subnet_choice);<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.setContext("subnet4", my_subnet_choice);<o:p></o:p></b></p>
<p class="MsoNormal"><b>}<o:p></o:p></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">But when I check the subnet in lease4_select KEA has change it to the one previously used:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>int lease4_select(CalloutHandle& handle) {<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.getArgument("subnet4", kea_subnet);<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.getContext("subnet4", my_subnet_choice);<o:p></o:p></b></p>
<p class="MsoNormal"><b><o:p> </o:p></b></p>
<p class="MsoNormal"><b>if(kea_subnet->getID() != my_subnet_choice->getID())<o:p></o:p></b></p>
<p class="MsoNormal"><b> {<o:p></o:p></b></p>
<p class="MsoNormal"><b> LOG_DEBUG(my_logger,50, LEASE4_SELECT_MISMATCH);<o:p></o:p></b></p>
<p class="MsoNormal"><b> handle.setContext(CONTEXT_PARAMETER_NAK, true);<o:p></o:p></b></p>
<p class="MsoNormal"><b> lease->decline(0);<o:p></o:p></b></p>
<p class="MsoNormal"><b> }<o:p></o:p></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I added this check & nak code in lease4_select and lease4_renew hooks to deal with the cases when a device is sending a renew message to force the client to send a discover message insted, but this ends in discover nak loop between KEA
and that client. I can resolve this behavior be reloading KEA or by removing that client record from the mem file.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Lease affinity is one thing I imagine could be in my way, but I believe I have turned it off with the following config and still seeing this behavior:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">"expired-leases-processing": {<o:p></o:p></p>
<p class="MsoNormal"> "flush-reclaimed-timer-wait-time": 0,<o:p></o:p></p>
<p class="MsoNormal"> "hold-reclaimed-time": 0,<o:p></o:p></p>
<p class="MsoNormal"> "max-reclaim-leases": 0,<o:p></o:p></p>
<p class="MsoNormal"> "max-reclaim-time": 0,<o:p></o:p></p>
<p class="MsoNormal"> "reclaim-timer-wait-time": 30,<o:p></o:p></p>
<p class="MsoNormal"> "unwarned-reclaim-cycles": 5<o:p></o:p></p>
<p class="MsoNormal"> }<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Any other ideas on what could explain this behavior? I see a DHCP4_SUBNET_DYNAMICALLY_CHANGED message in the provided logs that I would like to know more about.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here are some more logs to support my case:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">### kea dhcp log<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_BEGIN begin all callouts for hook subnet4_select<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUT_CALLED hooks library with index 1 has called a callout on hook subnet4_select that has address 0x7f491302ab5f (callout duration: 0.172 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_COMPLETE completed callouts for hook subnet4_select (total callouts duration: 0.172 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.packets/7456] DHCP4_SUBNET_SELECTED [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: the subnet with ID 6 was selected for client assignments<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.packets/7456] DHCP4_SUBNET_DATA [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: the selected subnet details:
<span style="background:yellow;mso-highlight:yellow">192.168.30.0/24</span><o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER get one host with IPv4 reservation for subnet id 6, identified by hwaddr=C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ALL_IDENTIFIER get all hosts with reservations using identifier: hwaddr=C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ALL_IDENTIFIER_COUNT using identifier hwaddr=C8D3FFEEFF4C, found 0 host(s)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER_NULL host not found using subnet id 6 and identifier hwaddr=C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER get one host with IPv4 reservation for subnet id 6, identified by client-id=01C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ALL_IDENTIFIER get all hosts with reservations using identifier: client-id=01C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ALL_IDENTIFIER_COUNT using identifier client-id=01C8D3FFEEFF4C, found 0 host(s)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.hosts/7456] HOSTS_CFG_GET_ONE_SUBNET_ID_IDENTIFIER_NULL host not found using subnet id 6 and identifier client-id=01C8D3FFEEFF4C<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.dhcp4/7456] DHCP4_CLASS_ASSIGNED [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: client packet has been assigned to the following class(es): UNKNOWN<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.dhcp4/7456] DHCP4_CLASS_ASSIGNED [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: client packet has been assigned to the following class(es): ALL, VENDOR_CLASS_MSFT 5.0,
UNKNOWN<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.ddns/7456] DHCP4_CLIENT_HOSTNAME_PROCESS [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: processing client's Hostname option<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.ddns/7456] DHCP4_CLIENT_HOSTNAME_DATA [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: client sent Hostname option: DESKTOP-FKUL6EB<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.ddns/7456] DHCP4_CLIENT_HOSTNAME_DATA [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: client sent Hostname option: DESKTOP-FKUL6EB<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.ddns/7456] DHCP4_RESPONSE_HOSTNAME_DATA [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: including Hostname option in the server's response: DESKTOP-FKUL6EB<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.dhcpsrv/7456] DHCPSRV_MEMFILE_GET_CLIENTID obtaining IPv4 leases for client ID 01:c8:d3:ff:ee:ff:4c<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.466 DEBUG [kea-dhcp4.dhcpsrv/7456] DHCPSRV_MEMFILE_GET_HWADDR obtaining IPv4 leases for hardware address hwtype=1 c8:d3:ff:ee:ff:4c<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.alloc-engine/7456] ALLOC_ENGINE_V4_OFFER_NEW_LEASE allocation engine will try to offer new lease to the client [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.dhcpsrv/7456] DHCPSRV_MEMFILE_GET_ADDR4 obtaining IPv4 lease for address
<span style="background:red;mso-highlight:red">10.206.0.13</span><o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_BEGIN begin all callouts for hook lease4_select<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUT_CALLED hooks library with index 1 has called a callout on hook lease4_select that has address 0x7f491302b6ca (callout duration: 0.146 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_COMPLETE completed callouts for hook lease4_select (total callouts duration: 0.146 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.dhcpsrv/7456] DHCPSRV_MEMFILE_GET_ADDR4 obtaining IPv4 lease for address 10.206.0.13<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.packets/7456] <span style="background:yellow;mso-highlight:yellow">
DHCP4_SUBNET_DYNAMICALLY_CHANGED</span> [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: changed selected subnet 192.168.30.0/24 to subnet 10.206.0.0/22 from shared network GR-Internet-AG06 for client assignments<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 INFO [kea-dhcp4.leases/7456] DHCP4_LEASE_ADVERT [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: lease 10.206.0.13 will be advertised<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.ddns/7456] DHCP4_RESPONSE_HOSTNAME_GENERATE [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: server has generated hostname myhost-10-206-0-13 for the client<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_BEGIN begin all callouts for hook pkt4_send<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUT_CALLED hooks library with index 1 has called a callout on hook pkt4_send that has address 0x7f491302a4db (callout duration: 0.093 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.callouts/7456] HOOKS_CALLOUTS_COMPLETE completed callouts for hook pkt4_send (total callouts duration: 0.093 ms)<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.options/7456] DHCP4_PACKET_PACK [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: preparing on-wire format of the packet to be sent<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.packets/7456] DHCP4_PACKET_SEND [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: trying to send packet DHCPNAK (type 6) from 192.168.15.80:67 to 10.206.0.2:67 on interface
ens33<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.467 DEBUG [kea-dhcp4.packets/7456] DHCP4_RESPONSE_DATA [hwtype=1 c8:d3:ff:ee:ff:4c], cid=[01:c8:d3:ff:ee:ff:4c], tid=0xabef9463: responding with packet DHCPNAK (type 6), packet details: local_address=192.168.15.80:67,
remote_address=10.206.0.2:67, msg_type=DHCPNAK (6), transid=0xabef9463,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">### my hook log<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] start subnet4_select
<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] SUBNET4_SELECT_PROCESSING started processing subnet in shared-network<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] SUBNET4_SELECT_CAPACITY subnet: "10.206.0.0/22" , capacity: 1019<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] SUBNET4_SELECT_CAPACITY subnet: "192.168.30.0/24" , capacity: 245<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] SUBNET4_SELECT_ALLOWED using allowed subnet:
<span style="background:yellow;mso-highlight:yellow">192.168.30.0/24</span><o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] Start lease4_select
<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] LEASE4_SELECT_VIRKIR_SUBNET virkir selects this subnet: 192.168.30.0/24<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.463 DEBUG [kea-dhcp4.virkir-kea-hook/7456] LEASE4_SELECT_KEA_SUBNET kea want to select this subnet:
<span style="background:red;mso-highlight:red">10.206.0.0/22</span><o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.464 DEBUG [kea-dhcp4.virkir-kea-hook/7456] LEASE4_SELECT_MISMATCH there is a mismatch in subnet selection, clean database and respond with nak<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.464 DEBUG [kea-dhcp4.virkir-kea-hook/7456] pkt4_send Start
<o:p></o:p></p>
<p class="MsoNormal">2018-10-30 12:30:19.464 DEBUG [kea-dhcp4.virkir-kea-hook/7456] PKT4_SEND_NAK sending nak package to client: c8:d3:ff:ee:ff:4c<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:black">Regards, Hreiğar. </span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:8.0pt;color:#999999"></span><o:p></o:p></p>
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