tun setup (routing?) issue in head

I've updated my HEAD amd64 system from December's sources to something more recent
and I've got problems with security/vpnc. To be precise vpnc itself seems to work
as good as before but its post-connect script is now failing:

$ ifconfig tun0 inet 10.99.15.144 10.99.15.144 netmask 255.255.255.255 mtu 1412 up
ifconfig: ioctl (SIOCAIFADDR): File exists

Where tun0 is an interface created by vpnc.
ktrace gives this:
ifconfig CALL  socket(PF_INET,SOCK_DGRAM,IPPROTO_IP)
ifconfig RET   socket 3
ifconfig CALL  ioctl(0x3,SIOCSIFMTU,0x525a60)
ifconfig RET   ioctl 0
ifconfig CALL  ioctl(0x3,SIOCGIFFLAGS,0x7fffffffda30)
ifconfig RET   ioctl 0
ifconfig CALL  ioctl(0x3,SIOCSIFFLAGS,0x7fffffffda30)
ifconfig RET   ioctl 0
ifconfig CALL  ioctl(0x3,SIOCDIFADDR,0x525380)
ifconfig RET   ioctl -1 errno 49 Can't assign requested address
ifconfig CALL  ioctl(0x3,SIOCAIFADDR,0x525340)
ifconfig RET   ioctl -1 errno 17 File exists
ifconfig CALL  write(0x2,0x7fffffffd2d0,0xa)

So, what's happening?
Do you I have to update the ifconfig command?
Or is there some issue in the networking code?

BTW, I also get the following messages in the system log when vpnc is started:
kernel: tun0: link state changed to UP
kernel: ifa_add_loopback_route: insertion failed
I have net.link.tap.up_on_open=1 in sysctl.conf if that matters.

-- 
Andriy Gapon