kern/188032: IPv6 on lo never leaves 'tentative' state if configured with prefixlen 128

[Andrey V. Elsukov]

The following reply was made to PR kern/188032; it has been noted by GNATS.

From: "Andrey V. Elsukov" <bu7cher at yandex.ru>
To: Darren Baginski <kickbsd at yandex.ru>, 
 freebsd-gnats-submit at FreeBSD.org
Cc:  
Subject: Re: kern/188032: IPv6 on lo never leaves 'tentative' state if configured
 with prefixlen 128
Date: Mon, 31 Mar 2014 12:11:14 +0400

 > IPv6 on lo never leaves 'tentative' state if configured with prefixlen 128.
 > 
 > Steps to reproduce.
 > 
 > # ifconfig lo8 create
 > # ifconfig lo8 up
 > # ifconfig lo8 inet6 fc00::ff prefixlen 128
 > 
 > 
 > # ifconfig lo8
 > lo8: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
 >         options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6>
 >         inet6 fc00::ff prefixlen 128 tentative 
 >         nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
 > 
 > 
 > lo8 ipv6 stays 'tentative' stays forever and never become ping-able.
 > 
 > "Workaround" is to apply any other prefixlen, e.g. /127 
 >> How-To-Repeat:
 > 
 > # ifconfig lo8 create
 > # ifconfig lo8 up
 > # ifconfig lo8 inet6 fc00::ff prefixlen 128
 > 
 > 
 > # ifconfig lo8
 > lo8: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
 >         options=600003<RXCSUM,TXCSUM,RXCSUM_IPV6,TXCSUM_IPV6>
 >         inet6 fc00::ff prefixlen 128 tentative 
 >         nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
 > 
 > # ping fc00::ff
 >> Fix:
 > "Workaround" is to apply any other prefixlen, e.g. /127 
 
 Hello,
 
 Actually the problem is in your configuration. As you may see, you have
 IFDISABLED flag set. When you are configuring /127 prefix, the system
 does install route on that prefix and automatically clears IFDISABLED
 flag. When you are configuring /128 prefix, the system won't install
 route and thus IFDISABLED flag still here. With IFDISABLED flag the
 system won't do DAD and  tentative flag will never cleared.
 
 -- 
 WBR, Andrey V. Elsukov