Virtual Router DHCP is not properly configured

[baby-gnu]

Problem

The DNS and default route are not announced

To reproduce

1. Configure 2 networks A and B,
2. Start a virtual router
   1. plug first interface to network A
   2. plug second interface to network B
   3. enable DHCPv4
   4. set DHCP on interface eth1
   5. enable DNS
   6. set DNS on interface eth1
   7. start the router

DHCPv4 configuration

/etc/one-appliance/service.d/VRouter/DHCP4v2/coredhcp-onelease/onelease-config.yml

---
eth1:
  server4:
    listen:
    - "%eth1"
    plugins:
    - lease_time: 3600s
    - server_id: 10.4.2.100
    - mtu: 1500
    - netmask: 255.0.0.0
    - onelease: leases-eth1.sqlite3 10.0.0.2 10.255.255.254 3600s --excluded-ips 10.4.2.100
        --mac2ip --mac2ip-prefix 02:00

Proposal

When DHCP is enabled:

• the ONEAPP_VNF_DHCP4_GATEWAY should default to the router interface on the network
• the ONEAPP_VNF_DHCP4_DNS should default to the router interface on the network if ONEAPP_VNF_DNS_ENABLED is YES

Workaround

Set ONEAPP_VNF_DHCP4_GATEWAY and ONEAPP_VNF_DHCP4_DNS manually after the router is started which result in the following configuration

/etc/one-appliance/service.d/VRouter/DHCP4v2/coredhcp-onelease/onelease-config.yml

---
eth1:
  server4:
    listen:
    - "%eth1"
    plugins:
    - lease_time: 3600s
    - server_id: 10.4.2.100
    - dns: 10.4.2.100
    - mtu: 1500
    - router: 10.4.2.100
    - netmask: 255.0.0.0
    - onelease: leases-eth1.sqlite3 10.0.0.2 10.255.255.254 3600s --excluded-ips 10.4.2.100
        --mac2ip --mac2ip-prefix 02:00

Diff between default and modified configuration

--- /etc/one-appliance/service.d/VRouter/DHCP4v2/coredhcp-onelease/onelease-config.yml.orig
+++ /etc/one-appliance/service.d/VRouter/DHCP4v2/coredhcp-onelease/onelease-config.yml
@@ -6,7 +6,9 @@
     plugins:
     - lease_time: 3600s
     - server_id: 10.4.2.100
+    - dns: 10.4.2.100
     - mtu: 1500
+    - router: 10.4.2.100
     - netmask: 255.0.0.0
     - onelease: leases-eth1.sqlite3 10.0.0.2 10.255.255.254 3600s --excluded-ips 10.4.2.100
         --mac2ip --mac2ip-prefix 02:00

[baby-gnu]

It could be interesting to be able to configure a DNS domain name to be used as search for clients.

[baby-gnu]

It could be interesting to be able to configure a DNS domain name to be used as search for clients.

unfortunately, coredns seems to not support DNS search option

[sk4zuzu]

Hi @baby-gnu 🤗

Please take a look here https://github.com/OpenNebula/one-apps/wiki/vr_dhcp4#virtual-router-configuration, I think you could try:

    ONEAPP_VNF_DHCP4_ENABLED = "YES"
    ONEAPP_VNF_DHCP4_INTERFACES = "eth1"
    ONEAPP_VNF_DHCP4_GATEWAY = "<ETH1_EP0>"
    ONEAPP_VNF_DHCP4_DNS = "<ETH1_EP0>"

So you dont have to provide specific/literal values, would that work for you? 🤔

[baby-gnu]

So you dont have to provide specific/literal values, would that work for you? 🤔

Yes, that's my workaround in the issue, I start the Virtual Router and then set context values with IP assigned by OpenNebula. I just want it to be more automatic.

[sk4zuzu]

I start the Virtual Router and then set context values with IP assigned by OpenNebula.

So, I'm saying that you don't have to deal with literal IP addresses as we implemented this https://github.com/OpenNebula/one-apps/wiki/vr_balancing#ip-addresses-placeholders also for DNS and DHCP modules. 👍 🙂

This is a static config, it's resolved inside the VR itself (at the runtime), so you can just add this literal config to your templates:

    ONEAPP_VNF_DHCP4_GATEWAY = "<ETH1_EP0>"
    ONEAPP_VNF_DHCP4_DNS = "<ETH1_EP0>"

In other words this triggers the automation you want, no? 🤔

[baby-gnu]

This is a static config, it's resolved inside the VR itself (at the runtime), so you can just add this literal config to your templates:

🤣 I overlooked the IP Address interpolation for Gateway and DNS and see <ETH1_EP0> as something to be replaced manually.

So, the mechanism is in place, could it be possible to define the per interface IP as default?

For users, when you start a router with DHCP on a network, it should be the default route and if it's configured as DHCP resolver, it should be announced in the DHCP too.

[sk4zuzu]

So, the mechanism is in place, could it be possible to define the per interface IP as default?

These ones should allow you to configure DHCP for specific VNETs attached to the VR:

ONEAPP_VNF_DHCP4_ETHx
ONEAPP_VNF_DHCP4_ETHx_DNS
ONEAPP_VNF_DHCP4_ETHx_GATEWAY
ONEAPP_VNF_DHCP4_ETHx_MTU

I hope that's somehow enough.. :)

For users, when you start a router with DHCP on a network, it should be the default route and if it's configured as DHCP resolver, it should be announced in the DHCP too.

We could in fact provide defaults inferred dynamically if all the metioned variables were undefined. 🤔 Let me think about it 👍 😇