FS#3744 - static IPv6 routes to gateways within the ULA address range are not restored on startup

[openwrt-bot]

eriktews:

Static IPv6 routes configured in /etc/config/network that use a gateway within the ula address range are not properly restored on startup.

I managed to reproduce the issue in 19.07.7 and in the latest snapshot (17-04-2021). To reproduce the issue, do the following:

Setup a new OpenWRT system, for example in a VM. Uplink connectivity is not required, which makes it easy to reproduce the bug in a VM. Then edit /etc/config/network and add an IPv6 route using a gateway within the ula range. For example the entries may look like this:

config globals 'globals'
        option ula_prefix 'fd22:e91a:3889::/48'

config route6
        option target "2001:4860:4860::8844"
        option gateway "fd22:e91a:3889::43"
        option interface "lan"

Reboot the device and verify that the route is not present with ip -6 route show. Then modify the config a bit, for example replace the 43 in the gateway address with 42. Then execute reload_config and wait a few seconds. Then verify that the route is present with ip -6 route show. You may then reboot the device and the route will not be there anymore.

[openwrt-bot]

eriktews:

Sorry for having used the wrong syntax. The config may look like this:

config globals 'globals'
option ula_prefix 'fd22:e91a:3889::/48'

config route6
option target "2001:4860:4860::8844"
option gateway "fd22:e91a:3889::43"
option interface "lan"


[openwrt-bot]

eriktews:

And one more note, everything is fine when using the link local address for the gateway.

[openwrt-bot]

eriktews:

I think after looking at the source code of netifd, I also know why this happens. First of all, the static IP addresses and routes for the interface are processed:

https://github.com/git-openwrt-org-mirror/netifd/blob/master/config.c#L744

Afterwards, the globals (which contain the ULA prefix) are initialized:

https://github.com/git-openwrt-org-mirror/netifd/blob/master/config.c#L746

The correct order might be to initialize the IP addresses first, then add the ULA prefix addresses from the //globals// and then add the routes.