[OpenAFS] Access an OpenAFS cell in LAN and WAN with dynamic DNS (DDNS) address

[Karl-Philipp Richter]

Hi,
I'm running a server with an OpenAFS volume which updates its IP which
is dynamically changed every 24 hours by the ISP using a dynamic DNS
(DDNS) service and `ddclient`. The server is a gateway for a LAN subnet
192.168.179.0/24. I access this server inside my LAN by adding the
192.168.179.0/24 address to `CellServDB` which works fine on client
inside 192.168.179.0/24. When I add the dynamic WAN IP of the server
when I'm outside LAN (e.g. in eduroam) to `CellServDB` on the client
side and reboot (and make sure that the IP didn't change after reboot)
I'm experiencing `ls: cannot access '/afs/richtercloud.de': Connection
timed out` when I invoke `ls /afs/` and see

    [  130.010338] afs: Lost contact with file server 192.168.178.20 in
cell richtercloud.de (code -1) (multi-homed address; other same-host
interfaces maybe up)
    [  130.010343] RXAFS_GetCapabilities failed with code -1
    [  186.461024] afs: Lost contact with file server 192.168.179.1 in
cell richtercloud.de (code -1) (all multi-homed ip addresses down for
the server)

in `dmesg`.

I tried adding all LAN IPs of the server and the WAN IP to `CellServDB`
in `[]` and not in all possible combinations. I configured my WiFi
router to forward UDP for port 7000 to 7008 (inclusively) and 88 and 750
(following https://wiki.openafs.org/AFSServicePorts/) to the server's
interface and setup the same forwarding on the server.

-Kalle