Execute script after DHCPv6 lease renewal?

[i0ntempest]

Is there a simple way to execute a script after odhcp6c client renews its lease? Reason I ask this is because I have a ULA range setup in my network and every time odhcp6c renews its lease my ULA prefix on br0 gets cleared. This renew does not appear to trigger any user scripts.
I know that odhcp6c executes /tmp/dhcp6c (a symlink to rc) for status updates, but the arguments passed to odhcp6c seems to be hardcoded into the rc binary so there’s no simple way to change it.
I have a BE88U running latest Merlin firmware (3006).
Thanks in advance.

 

[dave14305]

I’m not running 3006.103, but you should be able to use /jffs/scripts/dhcpc-event to capture the event (updated, bound, ra-updated, etc.) and the IP protocol (4 or 6).

Feb  9 19:09:50 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 10 06:30:01 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 11 19:09:52 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 12 06:30:01 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 13 19:09:54 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 14 06:30:01 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 15 19:09:56 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 16 06:30:01 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 17 19:09:57 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 18 06:30:01 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 19 19:10:01 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 20 06:30:02 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)
Feb 21 19:10:03 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 22 06:30:02 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)

 

[i0ntempest]

I’m not running 3006.103, but you should be able to use /jffs/scripts/dhcpc-event to capture the event (updated, bound, ra-updated, etc.) and the IP protocol (4 or 6).

I didn’t try but the official documentation says this works only with udhcpc, no mention of odhcp6c. You sure it’s going to work with DHCPv6?

 

[dave14305]

I didn’t try but the official documentation says this works only with udhcpc, no mention of odhcp6c. You sure it’s going to work with DHCPv6?

Here’s the code behind /tmp/dhcp6c

asuswrt-merlin.ng/release/src/router/rc/udhcpc.c at 81b835454d7e6d177397759d138bda204f8ac3cc · RMerl/asuswrt-merlin.ng

Third party firmware for Asus routers (newer codebase) - RMerl/asuswrt-merlin.ng

github.com

I also updated my earlier post to show logs of it being invoked when my DHCPv6 lease is updated.

 

[i0ntempest]

Here’s the code behind /tmp/dhcp6c

asuswrt-merlin.ng/release/src/router/rc/udhcpc.c at 81b835454d7e6d177397759d138bda204f8ac3cc · RMerl/asuswrt-merlin.ng

Third party firmware for Asus routers (newer codebase) - RMerl/asuswrt-merlin.ng

github.com

I also updated my earlier post to show logs of it being invoked when my DHCPv6 lease is updated.

Thank you. Based on your reply I have created dhcpc-event script with content:

#!/bin/sh
if ([ "$1" = "bound" ] || [ "$1" = "updated" ] || [ "$1" = "rebound" ]) && [ "$2" = "6" ]; then
    ip -6 addr add dev br0 fd00:d:e:f::1/64
fi

But this does not seem to work, the prefix still gets cleared. In the syslog this is what happens when v6 gets renewed:

Feb 24 15:35:04 odhcp6c[5183]: Server returned message status 0 
Feb 24 15:35:04 custom_script: Running /jffs/scripts/dhcpc-event (args: updated 6)
Feb 24 15:35:04 custom_script: Running /jffs/scripts/dhcpc-event (args: renew 4)

If `/tmp/dhcp6c updated` is the only thing that was executed when v6 lease renews, then looking at the code, there should be no `ip -6 addr flush` command issued, but there clearly is. That aside, the script seems to be executed too early so that the flush happens after the script. I guess adding a 5s delay to the `ip -6 addr add` would work, but is there a better way?