[FROG] BFD in a VRF not listening for port 3784/4784

Andrew Denton andrewd at sterling.net
Wed Apr 7 18:41:57 UTC 2021


Hi,

I'm running frr 7.5.1 and trying to configure BFD for an interface in a VRF. BFD counters don't show any "Control packet input" packets, and I think this is because FRR needs to listen on port 3784 inside the VRF, it's non-VRF socket won't receive any packets from the VRF. I manually tested this idea with "netcat -ul 3784", and I was only able to receive BFD packets if I create the netcat listening socket within the VRF (e.g. "ip vrf exec myvrf netcat -ul 3784"). BFDD does create a socket in the VRF, but it's for a high port not for 3784/4784. I'm running on RHEL8 / kernel 4.18.0-240.15.1.el8_3.x86_64 and using FRR from rpm.frrouting.org/repo/el8. Is there some config I'm missing, or should I file this as a bug?


For example,

bfd
  peer 192.0.2.12 vrf myvrf interface enp4s0f1

Results in

# ss -abnp | fgrep bfd

udp UNCONN 0 0 0.0.0.0%myvrf:49155 0.0.0.0:* users:(("bfdd",pid=160681,fd=26))

udp UNCONN 0 0 0.0.0.0:3784 0.0.0.0:* users:(("bfdd",pid=160681,fd=14))
udp UNCONN 0 0 0.0.0.0:3785 0.0.0.0:* users:(("bfdd",pid=160681,fd=18))
udp UNCONN 0 0 [::]:4784 [::]:* users:(("bfdd",pid=160681,fd=17))
udp UNCONN 0 0 [::]:3784 [::]:* users:(("bfdd",pid=160681,fd=16))
udp UNCONN 0 0 [::]:3785 [::]:* users:(("bfdd",pid=160681,fd=19))



# vtysh -c "show bfd peers counter"
peer 192.0.2.12 multihop local-address 192.0.2.13 vrf internet
Control packet input: 0 packets
Control packet output: 5140 packets
Echo packet input: 0 packets
Echo packet output: 0 packets
Session up events: 0
Session down events: 0
Zebra notifications: 2

Compare with BGP, which does work for me in a VRF because it listens on port 179 inside the VRF.

# ss -abnp 'sport = :179'
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
tcp LISTEN 0 128 0.0.0.0%myvrf:179 0.0.0.0:* users:(("bgpd",pid=160658,fd=26))
tcp LISTEN 0 128 [::]%myvrf:179 [::]:* users:(("bgpd",pid=160658,fd=27))


Thank you,
Andrew
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