Tinc route disappearing after some time

[Diaoul Ael]

Hello,

I have the route created by tinc in router mode disappearing after some
time with a rather simple configuration.

I want to join two (or more) networks accross the internet, primarily to
access network shares. Those networks have their own DHCPs and are
autonomous, i.e. not dependent on the VPN connection.
I think Tinc in router mode is best suited for my case and this example
<https://www.tinc-vpn.org/documentation/Example-configuration.html#Example-configuration>
perfectly describes my situation. Please let me know if you can think of
better alternatives as I'm out of my depth.

*Here is my setup :*

*Network A :* 10.0.0.0/16
*Network B : *10.1.0.0/16

*RPi with Tinc on A :* 10.0.1.6
*RPi with Tinc on B : *10.1.0.5

*tinc-up on A :* ifconfig $INTERFACE 10.0.1.6 netmask 255.0.0.0
*tinc-up on B :* ifconfig $INTERFACE 10.1.0.5 netmask 255.0.0.0

*hosts/A :*
Address = ...
Subnet = 10.0.0.0/16

*hosts/B :*
Address = ...
Subnet = 10.1.0.0/16

*tinc.conf A :*
Name = A

*tinc.conf B :*
Name = B
ConnectTo = A

Tinc connects perfectly and everything works fine, here is the routing
table:
$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
default         box             0.0.0.0         UG    202    0        0 eth0
10.0.0.0        0.0.0.0         255.0.0.0       U     0      0        0 tinc
10.1.0.0        0.0.0.0         255.255.255.0   U     202    0        0 eth0

After some time, the route disappears *in B only*. The logs (debug level 3)
shows nothing and in ifconfig on the tinc interface I'm left with the
inet6, no more inet :
$ ifconfig
tinc: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
        inet6 xxxx::yyyy:xxxx:yyyy:xxxx  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen
500  (UNSPEC)
        RX packets 11845  bytes 729085 (711.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 324  bytes 40046 (39.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

I haven't seen any particular event that cause this, system log files don't
show anything particular, I don't know where else to look. What can cause
the route to disappear like that? I suppose some kind of conflict? Or maybe
the "box" router on the B side?

Thanks in advance for your help troubleshooting this!
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