problem with fin+ack with TSO on em 82573

I have some web servers, each with two of the following on them:

em0_at_pci0:3:0:0: class=0x020000 card=0x61801462 chip=0x108b8086 rev=0x03
hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'PC82573V Intel network controller (PCIE Gigabit Ethernet)'
    class      = network
    subclass   = ethernet

When TSO is enabled on the interface I have some last ACK problems with some
clients.  Basically the ack no. doesn't appear to increment with TSO on.  
172.16.17.1 is the freebsd-current box (as of 3/5/2008).

This is a dump from the 172.16.18.144 box.   When I dump from the view of
(172.16.17.1) the freebsd box, the resulting  appears to lie about the
packet ordering, showing it sending the Fin first.  Turn TSO off it appears
to tell the truth.  I don't trust tcpdump with tso/rxcsum/txcsum on anyway.

172.16.18.144.10408 > 172.16.17.1.http: F 312:312(0) ack 39247 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.18.144.10408 > 172.16.17.1.http: F 312:312(0) ack 39247 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.18.144.10408 > 172.16.17.1.http: F 312:312(0) ack 39247 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.18.144.10408 > 172.16.17.1.http: F 312:312(0) ack 39247 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.18.144.10408 > 172.16.17.1.http: F 312:312(0) ack 39247 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
(DF)
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535
172.16.17.1.http > 172.16.18.144.10408: F 39247:39247(0) ack 312 win 65535

-- 
Mark Atkinson
atkin901_at_yahoo.com
(!wired)?(coffee++):(wired);