kern/57037: unncessary and unwarranted RTM_NEWADDR for IPv6 routing messages

[kardel%netbsd.org@localhost]

>Number:         57037
>Category:       kern
>Synopsis:       IPv6 autoconfig causes RTM_NEWADDR messages every 2 minutes (unnecessary and unwarranted)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 30 09:25:00 +0000 2022
>Originator:     kardel%netbsd.org@localhost
>Release:        NetBSD 9.99.100
>Organization:
>Environment:
System: NetBSD styxnew 9.99.100 NetBSD 9.99.100 (GENERIC) #1: Sat Sep 24 09:01:07 UTC 2022 kardel@gaiatest:/src/NetBSD/current/src/obj.amd64/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
	When using auto configured IPv6 addresses RTM_NEWADDR messages show up about every 2 minutes.
	No intervening RTM_DELADDR messages are sent inbetween. if_watchd triggers on these causing
	scripts to needlessly run on an unchanged network situation.
	These message should not be sent unless a real change happens.
>How-To-Repeat:
	let NetBSD autoconfigure IPv6 and watch "route monitor".

RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:24:57 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:24:57 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:26:58 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:26:58 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:28:59 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:28:59 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:31:00 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:31:00 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:33:02 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:33:02 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>
 ffff:ffff:ffff:ffff:: aa:00:00:00:00:01 xxxx:yyyy:zzzz:rrrr:ssss:tttt:uuuu:vvvv
got message of size 112 on Fri Sep 30 08:35:03 2022
#12: len 112, got message of size 120 on Fri Sep 30 08:35:03 2022
RTM_NEWADDR: address being added to iface: len 120, pid 1709, metric 0, addrflags: 0x40<AUTOCONF>
sockaddrs: 0x34<NETMASK,IFP,IFA>

>Fix:
	check IPv6 autoconfiguration code?