ABI differences between stable/10 and head?

Yesterday, I upgraded the kernel on my sparc64 to -head,
so I was running a mis-matched kernel and userland.
The userland was a recent (as of two days ago) stable/10.

In the nightly report, I noticed the following:

> Network interface status:
> Name    Mtu Network       Address              Ipkts Ierrs Idrop    Opkts Oerrs  Coll  Drop
> bge0      - <Link#1>      00:03:ba:e0:ce:07        0 64691     0        0     0 11494817 2025493932409880576
> bge0      - fe80::203:baf fe80::203:baff:fe        0     -     -        0     -     -     -
> bge0      - spork.pix.net 2001:470:e254:10:        0     -     -        0     -     -     -
> bge0      - 192.168.16.0  spork                    0     -     -        0     -     -     -
> bge1      - <Link#2>      00:03:ba:e0:ce:08        0     0     0        0     0     0 4040291828690585088
> bge2      - <Link#3>      00:03:ba:e0:ce:09        0     0     0        0     0     0 4040291832985552384
> bge3      - <Link#4>      00:03:ba:e0:ce:0a        0     0     0        0     0     0 4040291837582442496
> lo0       - <Link#5>                               0    74     0        0     0 38794 2025493932409880576
> lo0       - localhost     ::1                      0     -     -        0     -     -     -
> lo0       - fe80::1%lo0   fe80::1%lo0              0     -     -        0     -     -     -
> lo0       - your-net      localhost                0     -     -        0     -     -     -

As you can see, the "drop" column for the host has
completely outrageous values.

When representing those numbers as binary, there's
an awful lot of zeros in the low order bits, like
some structure is being referenced off by a word or
two.

lidl_at_torb-142: bc -l
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
obase=2
2025493932409880576
1110000011100000000000000000000000000000000000000000000000000

I also find it more than slightly curious that the "drop" values for
bge0 and lo0 are identical.

Do we have some subtle ABI differences between the two systems
(stable/10 vs -head)?

-Kurt