BSR elected RP doesn't see itself as RP

[michaelinoue]

Description

When switching RPs, sometimes the failover RP does not view itself as the RP for a group.

Version

frr-10.2

How to reproduce

Add a candidate bsr. e.g.

host1# conf
host1(config)# router pim6
host1(config-pim6)# bsr candidate-bsr

Add a candidate RP, e.g.

host2# conf
host2(config)# router pim6
host2(config-pim6)# bsr candidate-rp ff08::/16 priority 0

Add another candidate RP with a higher priority (the "failover" RP when the primary RP goes down), e.g.

host3# conf
host3(config)# router pim6
host3(config-pim6)# bsr candidate-rp ff08::/16 priority 255

After host 1 is elected the RP, down it somehow (e.g. turn off the host or disconnect it). The election process should begin, with host 3 being elected. Indeed we see that host 3 was elected; however, host 3 itself does not view itself as the RP:

host3# show ipv6 pim rp-info
 RP address             group/prefix-list  OIF      I am RP  Source  Group-Type  
 fd28:1d07:cc94:f900::  ff08::/16          Unknown  no       BSR     ASM        

host3# show int lo
Interface lo is up, line protocol is up
  Link ups:       0    last: (never)
  Link downs:     0    last: (never)
  vrf: default
  index 1 metric 0 mtu 65536 speed 0 txqlen 1000
  flags: <UP,LOWER_UP,LOOPBACK,RUNNING>
  Type: Loopback
  inet6 fd28:1d07:cc94:f900::/56
  Interface Type Other
  Interface Slave Type None
  protodown: off 

Expected behavior

Expecting host 3 to view itself as the RP and behave as the RP.

Actual behavior

Host 3 does not view itself as the RP nor behave as the RP.

Additional context

No response

Checklist

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