kern/50549: ndp(8) lists entries of link-local addresses but fails to get a specific entry

[ozaki-r%netbsd.org@localhost]

>Number:         50549
>Category:       kern
>Synopsis:       ndp(8) lists entries of link-local addresses but fails to get a specific entry
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Dec 14 07:55:00 +0000 2015
>Originator:     Ryota Ozaki
>Release:        NetBSD-7.0_RELEASE and above
>Organization:
>Environment:
NetBSD netbsd7 7.0.0_PATCH NetBSD 7.0.0_PATCH (GENERIC.201512132100Z) amd64

>Description:
On a NetBSD 6.x machine, ndp -n <link-local-address> works:

netbsd6# ndp -n -a
Neighbor                             Linklayer Address  Netif Expire    S Flags
fe80::5054:ff:fedc:25e3%vioif0       52:54:00:dc:25:e3 vioif0 permanent R 
fe80::5054:ff:fefe:4a97%vioif1       52:54:00:fe:4a:97 vioif1 permanent R 
fe80::1%lo0                          (incomplete)         lo0 permanent R 
netbsd6# ndp -n fe80::5054:ff:fedc:25e3%vioif0
Neighbor                             Linklayer Address  Netif Expire    S Flags
fe80::5054:ff:fedc:25e3%vioif0       52:54:00:dc:25:e3 vioif0 permanent R 

However, since 7.0_RELEASE, it doesn't work:

netbsd7# ndp -n -a
Neighbor                             Linklayer Address  Netif Expire    S Flags
fe80::5054:ff:fef3:d81c%vioif0       52:54:00:f3:d8:1c vioif0 permanent R 
fe80::1%lo0                          (incomplete)         lo0 permanent R 
netbsd7# ndp -n fe80::5054:ff:fef3:d81c%vioif0
Neighbor                             Linklayer Address  Netif Expire    S Flags
ndp: fe80::5054:ff:fef3:d81c%vioif0 (fe80::5054:ff:fef3:d81c) -- no entry

(I tested only on 7.0.0_PATCH (GENERIC.201512132100Z) but my colleague confirmed
that the issue happens on 7.0_RELEASE too.)
>How-To-Repeat:
See above.
>Fix:
N/A