ARP resolution not done from one end

[Nick Hibma]

Folks,

We have a setup where each mobile node connects with 1 or more tinc instances (over different links) to a central node. tinc is running in switch mode. The link is chosen by setting the IP address on the active link's interface, and the central node sees this after the first packet on the link, and moves the MAC address to a different 'ethernet port' (link). This works really well, and keeps webmal sessions alive on a moving ship (VSat -> 3G -> VSat).

We have changed our setup and now the tunnel becomes idle for long periods of time. The problem is that the central node expires it's ARP table entry for the node. tinc is not forwarding ARP requests over the link / links. After doing 1 ping from the mobile node to the central node the ARP entry is there again as that end does forward ARP requests, and things are back to normal. The roaming node seems to initiate ARP resolution, while the central node does not.

Any points as to why the central tinc is not doing / able to do the ARP request?


tinc.conf on the central node:

Device = /dev/tap1
Name = centralnode
Mode = switch
DirectOnly = yes
TunnelServer = yes
PingInterval = 60
PingTimeout = 15
ReplayWindow = 0

BindToAddress = 192.168.50.82
BindToAddress = 192.168.50.84
BindToAddress = 192.168.50.83


tap1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=80000<LINKSTATE>
	ether 42:00:00:00:00:00
	inet 192.168.51.1 netmask 0xffffff00 broadcast 192.168.51.255
	Opened by PID 51917


tinc.conf for the first link on the mobile node:

Name = mobilenode1_1
ConnectTo = centralnode
PrivateKeyFile = /usr/local/etc/tinc/VSat/rsa_key.priv.mobilenode1_1

Device = /dev/tap1
Mode = switch

DirectOnly = Yes
TunnelServer = Yes
PingTimeout = 15
ReplayWindow = 0


tap1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=80000<LINKSTATE>
	ether 42:00:00:00:01:bf
	inet 192.168.51.191 netmask 0xffffff00 broadcast 192.168.51.255
	Opened by PID 1018
tap2: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=80000<LINKSTATE>
	ether 42:00:00:00:02:bf
	Opened by PID 1026
etc.

Regards,

Nick Hibma
AnyWi Technologies