[ERROR] inject-add2: File exists / [ERROR] inject-upd2: Device or resource busy

[Bernd Naumann <bena@xxxxxxxxxxxxxxx>]

Hi *,

I see some of these error messages every couple of minutes, in the range 
of 1 in 2-3 minutes and 2-3 per minute.
Sometimes at the same time on both peers, sometimes not.

At first I thought it is somehow related to increasing "no space left in 
cache", and so I doubled and doubled `HashSize` and `HashLimit` till I 
did not saw creation failed or update failed when running `conntrackd -s 
cache` any longer.

However, chances are high both have nothing to do with each other.
I do not even know if this is a really a thing to be concerned about.
AFAIK conntrackd re-tries to create/inject/update in case of an error...


What could be / is the reason of these errors "inject-add2: File exists" 
and "inject-upd2: Device or resource busy"?


What information can I provide in addition?

The two systems run conntrackd 1.4.5 on a Debian 10 with kernel 5.7

/proc/sys/net/netfilter/nf_conntrack_max
1048576


General {
  HashSize 1048576
  HashLimit 2097152

  LogFile on
  LockFile /var/lock/conntrackd.lock
  UNIX {
    Path /var/run/conntrackd.sock
    Backlog 20
  }

  NetlinkBufferSize 2097152
  NetlinkBufferSizeMaxGrowth 8388608
  NetlinkOverrunResync on
  NetlinkEventsReliable on

  Filter From Kernelspace {
    Protocol Accept {
      TCP
      UDP
      ICMP
      IPv6-ICMP
    }

    Address Ignore {
      IPv4_address 127.0.0.0/8
      IPv4_address PEER_1_LAN/32
      IPv4_address PEER_2_LAN/32
      IPv4_address PEER_1_WAN_1/32
      IPv4_address PEER_2_WAN_1/32
      IPv4_address PEER_1_WAN_2/32
      IPv4_address PEER_2_WAN_2/32
      IPv4_address 169.254.0.0/16
      IPv6_address ::1
    }
  }
}

Sync {
  Mode FTFW {
    DisableExternalCache on
  }

  UDP {
    IPv4_address PEER_1_LAN
    IPv4_Destination_Address PEER_2_LAN
    Port 3780
    Interface lan0
    SndSocketBuffer 1249280
    RcvSocketBuffer 1249280
    Checksum on
  }

  Options {
    TCPWindowTracking on
    ExpectationSync On
  }
}


Thanks for reading and any hints you may can provide.
Bernd