zebra: IP address is not assigned if interface is up

[glazychev-art]

Description

Hello, I've found a problem with zebra interface settings. IP address is not assigned after interface down and up.

Version

FRRouting 9.1.1

How to reproduce

Steps to reproduce:

1. Run frr with frr.conf:

   interface dum1
   ipv6 address fc00:1::1/64
   exit

2. ip link add name dum1 type dummy
3. Make sure, that fc00:1::1/64 has been assigned
4. ip link set dev dum1 down
5. ip link set dev dum1 up
6. fc00:1::1/64 is not assigned

Expected behavior

IP address is assigned

Actual behavior

IP address is not assigned

Additional context

I looked at zebra/interface.c. Most likely there is a problem with ZEBRA_INTERFACE_ACTIVE flag. Is it valid to unset ZEBRA_INTERFACE_ACTIVE in case of interface down?

Checklist

• [X] I have searched the open issues for this bug.
• [X] I have not included sensitive information in this report.