Frr bgp session in Active forever:

BGP neighbor on eth5: 100.65.0.10, remote AS 0, local AS 64999, internal link  
  Local Role: undefined                                                        
  Remote Role: undefined                                                       
 Member of peer-group downlink for session parameters                          
  BGP version 4, remote router ID 0.0.0.0, local router ID 192.168.111.36      
  BGP state = Active                                                           
  Last read 15:16:15, Last write never    

...

Bfd session don't exist or in down status.

[root@r0-compute-0 ~]# podman exec -t -i -u root frr vtysh -c "show bfd peers brief"
Session count: 2
SessionId  LocalAddress                             PeerAddress                             Status         
=========  ============                             ===========                             ======         
3240854396 100.64.0.2                               100.64.0.1                              down           
1888762429 100.65.0.2                               100.65.0.1                              down           

frr version broken:

frr-8.5.3-4.el9_4.2.x86_64

Previous version working:

frr-8.5.3-4.el9.x86_64

Error detected with BGP + BFD. Only BGP no error. We suspect from this patch:

https://patch-diff.githubusercontent.com/raw/FRRouting/frr/pull/18153.patch

and we supect same issue that this reported upstream:

https://github.com/FRRouting/frr/issues/18631

We've tested with frr version frr-10.3-01.el9.x86_64 and no error.

Log errors:

...

2025/04/09 12:49:54 BGP: [JFFAN-DEGED] eth4 sending OPEN, version 4, my as 64999, holdtime 180, id 192.168.111.36
2025/04/09 12:49:54 BGP: [T91AW-FGMHW] bgp_fsm_change_status : vrf default(0), Status: OpenSent established_peers 3
2025/04/09 12:49:54 BGP: [HKWM3-ZC5QP] eth4 fd 25 went from Connect to OpenSent
2025/04/09 12:49:54 BGP: [H4B4J-DCW2R][EC 33554455] eth4 [Error] bgp_read_packet error: Connection reset by peer
2025/04/09 12:49:54 BGP: [NTX3S-9Q8YV] eth4 [Event] BGP error 7 on fd 25
2025/04/09 12:49:54 BGP: [ZWCSR-M7FG9] eth4 [FSM] TCP_fatal_error (OpenSent->Active), fd 25
2025/04/09 12:49:54 BGP: [T91AW-FGMHW] bgp_fsm_change_status : vrf default(0), Status: Active established_peers 3
2025/04/09 12:49:54 BGP: [HKWM3-ZC5QP] eth4 fd -1 went from OpenSent to Active

....

.......

incoming conn rejected - no AF activated for peer

.....

how to reproduce:

2 frr router connected with bgp and bfd and restart or link down/up.

conf examples:

R1

hostname spine-0
log file /var/log/frr/frr.log
service integrated-vtysh-config
line vty
frr version 7.0

debug bfd peer
debug bfd network
debug bfd zebra

debug bgp graceful-restart
debug bgp neighbor-events
debug bgp updates
debug bgp update-groups

router bgp 65000
  bgp log-neighbor-changes
  bgp graceful-shutdown

  neighbor downlink peer-group
  neighbor downlink remote-as external
  neighbor downlink bfd
  neighbor downlink bfd profile tripleo
  ! neighbor downlink capability extended-nexthop
  neighbor eth1 interface peer-group downlink

  neighbor uplink peer-group
  neighbor uplink remote-as internal
  neighbor uplink bfd
  neighbor uplink bfd profile tripleo
  ! neighbor uplink capability extended-nexthop
  neighbor eth7 interface peer-group uplink

  address-family ipv4 unicast
    redistribute connected
    neighbor downlink default-originate
    neighbor downlink prefix-list only-host-prefixes in
    neighbor uplink prefix-list only-default-host-prefixes in
    neighbor uplink next-hop-self
  exit-address-family

  address-family ipv6 unicast
    redistribute connected
    neighbor downlink activate
    neighbor downlink default-originate
    neighbor downlink prefix-list only-host-prefixes in
    neighbor uplink activate
    neighbor uplink prefix-list only-default-host-prefixes in
  exit-address-family

  address-family l2vpn evpn
    neighbor downlink activate
    neighbor uplink activate
  exit-address-family

ip prefix-list only-default-host-prefixes permit 0.0.0.0/0
ip prefix-list only-default-host-prefixes permit 0.0.0.0/0 ge 32
ip prefix-list only-host-prefixes permit 0.0.0.0/0 ge 32

ipv6 prefix-list only-default-host-prefixes permit ::/0
ipv6 prefix-list only-default-host-prefixes permit ::/0 ge 128
ipv6 prefix-list only-host-prefixes permit ::/0 ge 128

ip nht resolve-via-default

bfd
  profile tripleo
    detect-multiplier 10
    transmit-interval 500
    receive-interval 500

R2

hostname leaf-0                              
log file /var/log/frr/frr.log                
service integrated-vtysh-config              
line vty                                     
frr version 7.0
                                                                               
debug bfd peer                      
debug bfd network    
debug bfd zebra                      
                                                                               
debug bgp graceful-restart                 
debug bgp neighbor-events                  
debug bgp updates
debug bgp update-groups      
                                                                               
router bgp 64999                            
  bgp log-neighbor-changes             
  bgp graceful-shutdown            
                                                                               
  bgp graceful-restart               
  bgp graceful-restart notification                          
  bgp graceful-restart restart-time 60
  bgp graceful-restart preserve-fw-state
  ! bgp long-lived-graceful-restart stale-time 15
                                                                              
                                                                               
  neighbor uplink peer-group
  neighbor uplink remote-as external 
  neighbor uplink bfd         
  neighbor uplink bfd profile tripleo       
  ! neighbor uplink capability extended-nexthop
  neighbor eth1 interface peer-group uplink
  neighbor eth2 interface peer-group uplink               
                                                                               
  address-family ipv4 unicast                           
    redistribute connected
    neighbor uplink allowas-in origin
    neighbor uplink prefix-list only-default-host-prefixes in
  exit-address-family
                                                                               
  address-family ipv6 unicast
    redistribute connected
    neighbor uplink activate
    neighbor uplink allowas-in origin
    neighbor uplink prefix-list only-default-host-prefixes in
  exit-address-family

  address-family l2vpn evpn
    neighbor uplink activate
    neighbor uplink allowas-in origin
  exit-address-family

ip prefix-list only-default-host-prefixes permit 0.0.0.0/0
ip prefix-list only-default-host-prefixes permit 0.0.0.0/0 ge 32
ip prefix-list only-host-prefixes permit 0.0.0.0/0 ge 32

ipv6 prefix-list only-default-host-prefixes permit ::/0
ipv6 prefix-list only-default-host-prefixes permit ::/0 ge 128
ipv6 prefix-list only-host-prefixes permit ::/0 ge 128

ip nht resolve-via-default

bfd
  profile tripleo
    detect-multiplier 10
    transmit-interval 500
    receive-interval 500