[Dnsmasq-discuss] DNS forwarding steered based on source interface?

[Christopher Hill]

Hi,

I have a question regarding if upstream DNS forwarding can be based on 
the source interface? Reading the manual I don't believe it is possible..?

The scenario I have is two VLANs that can talk to each other and both 
use dnsmasqfor local name resolution - this works fine. Each VLAN is 
configured at the gateway to default route traffic to different VPNs, 
e.g. VLAN1 out to VPN1, and VLAN2 to VPN2 respectively, and I would like 
dnsmasq to forward requests originating on VLAN1 to the DNS on VPN1, and 
the same for VLAN2 forwarding to VPN2.

To illustrate:

              tun1     VPN1   VPN2     tun2
              10.0.1.1  |       | 10.0.2.1
                        +---+---+
                            |
                           WAN
                            |
                    +-------+--------+
                    |      eth0      |
           VLAN 1 <-+-eth1      eth2-+-> VLAN 2
   192.168.1.0/24   |    (gateway)   |   192.168.2.0/24
                    +----------------+


I would like to do something like the following in the dnsmasq 
configuration on the gateway:

   server=eth1,10.0.1.1 at tun1
   server=eth2,10.0.2.1 at tun2

i.e. queries arriving on eth1 get sent to 10.0.1.1 via tun1, and queries 
arriving on eth2 get sent to 10.0.2.1 via tun 2.

Thanks,
Chris

N.B. I have considered running two instances (one bound to eth1 and 
another to eth2) but that duplicates setup and makes local queries 
across VLANs more complicated.