bin/53151: mdnsd tires to send on inactive (BACKUP state) CARP IP addresses

[bruce.lilly%gmail.com@localhost]

>Number:         53151
>Category:       bin
>Synopsis:       mdnsd tires to send on inactive (BACKUP state) CARP IP addresses
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 03 17:10:00 +0000 2018
>Originator:     Bruce Lilly
>Release:        7.1.2
>Organization:
none
>Environment:
NetBSD p867.blilly.net 7.1.2_PATCH NetBSD 7.1.2_PATCH (GENERIC) #0: Mon Apr  2 23:15:50 EDT 2018  root%e2300b.blilly.net@localhost:/usr/obj/sys/arch/i386/compile/GENERIC i386 i386 Intel 686-class NetBSD

[_PATCH and the build information is for the sole change to GENERIC to enable carp]
>Description:
mdnsd (/usr/sbin/mdnsd mDNSResponder (Engineering Build)) tries to send on IP addresses allocated to CARP virtual hosts even when the CARP interface is in the BACKUP state (i.e. inactive):

# ifconfig -a
re0: flags=8b43<UP,BROADCAST,RUNNING,PROMISC,ALLMULTI,SIMPLEX>re0: flags=8b43<MULTICAST> mtu 1500
        capabilities=3f80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx>
        capabilities=3f80<UDP4CSUM_Rx,UDP4CSUM_Tx>
        enabled=0
        ec_capabilities=3<VLAN_MTU,VLAN_HWTAGGING>
        ec_enabled=0
        address: 00:22:3f:f9:de:54
        media: Ethernet autoselect (1000baseT full-duplex)
        status: active
        inet 192.168.99.81 netmask 0xffffff00 broadcast 192.168.99.255
        inet6 fe80::222:3fff:fef9:de54%re0 prefixlen 64 scopeid 0x1
        inet6 2002:4474:ada0:0:222:3fff:fef9:de54 prefixlen 64 autoconf
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33192
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2
carp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        capabilities=3f80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx>
        capabilities=3f80<UDP4CSUM_Rx,UDP4CSUM_Tx>
        enabled=0
        carp: BACKUP carpdev re0 vhid 1 advbase 1 advskew 230
        address: 00:00:5e:00:01:01
        inet 192.168.99.220 netmask 0xffffff00 broadcast 192.168.99.255

2018-04-03T12:43:53.940917-04:00 p867.blilly.net mdnsd - - - mDNSPlatformSendUDP got error 51 (Network is unreachable) sending packet to 224.0.0.251 on interface 192.168.99.220/carp0/3
2018-04-03T12:43:53.940917-04:00 p867.blilly.net mdnsd - - - mDNSPlatformSendUDP got error 51 (Network is unreachable) sending packet to 224.0.0.251 on interface 192.168.99.220/carp0/3
2018-04-03T12:43:53.940917-04:00 p867.blilly.net mdnsd - - - mDNSPlatformSendUDP got error 51 (Network is unreachable) sending packet to 224.0.0.251 on interface 192.168.99.220/carp0/3
...

There is no reason for mdnsd (or anything other than the kernel) to attempt to send on an inactive CARP interface.
>How-To-Repeat:
Configure, build, and install a CARP-enabled kernel.
Configure a CARP virtual host on at least two machines on the same network.
Enable the CARP interfaces.
Start mdnsd on (one of) the backup machine(s).
Note logged error messages in /var/log/messages (quickly, berfore newsyslog removes them...)
>Fix: