I have a NetBSD/pc532 machine setup as a firewall with FWTK for a
MacOS/MacII, and have a problem with (at least) the http-gw transfers.
When I transfer a large amount of data from the Internet to the
pc532, or from the pc532 to the Mac, things are just fine.  However,
if I transfer from the Internet directly to the Mac, I see the
pc532 not bothering to ack most of it's packets on the first
reception.  The pc532 is idle, except for the standard things like
sendmail, inetd, etc. sleeping, and the active http-gw.

Here's a bit of the tcpdump I got, in case it helps.  As you can
see, things seem to be fine for a bit, and then the pc532 starts
waiting for the server to timeout and resend a packet before it
sends the ack.  (Look around 00:22 to 00:36.)  Is this a NetBSD
problem, a FWTK problem, or something I screwed up myself?  Any
hints on how to fix it?

Many thanks in advance,
Jon Buller <jonb@metronet.com>

00:16.060000 mac.1168 > pc532.http-gw: S 2517715824:2517715824(0) win 2920 <mss 1460>
00:16.060000 pc532.http-gw > mac.1168: S 1919744001:1919744001(0) ack 2517715825 win 17520 <mss 1460>
00:16.100000 mac.1168 > pc532.http-gw: . ack 1 win 2920
00:16.710000 mac.1168 > pc532.http-gw: . 1:325(324) ack 1 win 2920
00:16.760000 pc532.1206 > inet.www: S 1919936001:1919936001(0) win 16384 <mss 512>
00:16.800000 pc532.http-gw > mac.1168: . ack 325 win 17277
00:17.080000 inet.www > pc532.1206: S 421897350:421897350(0) ack 1919936002 win 61440 <mss 4312>
00:17.080000 pc532.1206 > inet.www: . ack 1 win 16384
00:17.090000 pc532.1206 > inet.www: P 1:58(57) ack 1 win 16384
00:17.550000 inet.www > pc532.1206: . ack 58 win 61440
00:17.550000 pc532.1206 > inet.www: P 58:303(245) ack 1 win 16384
00:18.120000 inet.www > pc532.1206: P 1:187(186) ack 303 win 61440
00:18.120000 pc532.1206 > inet.www: . ack 187 win 16198
00:18.130000 pc532.http-gw > mac.1168: P 1:18(17) ack 325 win 17520
00:18.160000 mac.1168 > pc532.http-gw: . ack 18 win 2920
00:18.160000 pc532.http-gw > mac.1168: P 18:49(31) ack 325 win 17520
00:18.180000 mac.1168 > pc532.http-gw: . ack 49 win 2920
00:18.180000 pc532.http-gw > mac.1168: P 49:89(40) ack 325 win 17520
00:18.210000 mac.1168 > pc532.http-gw: . ack 89 win 2920
00:18.210000 pc532.http-gw > mac.1168: P 89:136(47) ack 325 win 17520
00:18.240000 mac.1168 > pc532.http-gw: . ack 136 win 2920
00:18.240000 pc532.http-gw > mac.1168: P 136:185(49) ack 325 win 17520
00:18.270000 mac.1168 > pc532.http-gw: . ack 185 win 2920
00:18.270000 pc532.http-gw > mac.1168: P 185:187(2) ack 325 win 17520
00:18.290000 mac.1168 > pc532.http-gw: . ack 187 win 2920
00:18.530000 inet.www > pc532.1206: . 187:699(512) ack 303 win 61440
00:18.530000 pc532.http-gw > mac.1168: P 187:699(512) ack 325 win 17520
00:18.600000 pc532.1206 > inet.www: . ack 699 win 16384
00:18.690000 mac.1168 > pc532.http-gw: . ack 699 win 2920
00:19.710000 inet.www > pc532.1206: . 699:1211(512) ack 303 win 61440
00:20.040000 inet.www > pc532.1206: . 1211:1723(512) ack 303 win 61440
00:20.400000 inet.www > pc532.1206: . 1723:2235(512) ack 303 win 61440
00:20.730000 inet.www > pc532.1206: . 2235:2747(512) ack 303 win 61440
00:21.110000 inet.www > pc532.1206: . 2747:3259(512) ack 303 win 61440
00:21.500000 inet.www > pc532.1206: . 3259:3771(512) ack 303 win 61440
00:21.870000 inet.www > pc532.1206: . 3771:4283(512) ack 303 win 61440
00:22.240000 inet.www > pc532.1206: . 4283:4795(512) ack 303 win 61440
00:36.530000 inet.www > pc532.1206: . 699:1211(512) ack 303 win 61440
00:36.530000 pc532.http-gw > mac.1168: P 699:1211(512) ack 325 win 17520
00:36.560000 pc532.1206 > inet.www: . ack 1211 win 16384
00:36.680000 mac.1168 > pc532.http-gw: . ack 1211 win 2920
00:37.250000 inet.www > pc532.1206: . 1211:1723(512) ack 303 win 61440
00:37.250000 pc532.http-gw > mac.1168: P 1211:1723(512) ack 325 win 17520
00:37.360000 pc532.1206 > inet.www: . ack 1723 win 16384
00:37.400000 mac.1168 > pc532.http-gw: . ack 1723 win 2920
00:38.020000 inet.www > pc532.1206: . 1723:2235(512) ack 303 win 61440
00:38.330000 inet.www > pc532.1206: . 2235:2747(512) ack 303 win 61440
00:57.550000 inet.www > pc532.1206: . 1723:2235(512) ack 303 win 61440
00:57.550000 pc532.http-gw > mac.1168: P 1723:2235(512) ack 325 win 17520
00:57.570000 pc532.1206 > inet.www: . ack 2235 win 16384
00:57.700000 mac.1168 > pc532.http-gw: . ack 2235 win 2920
00:58.230000 inet.www > pc532.1206: . 2235:2747(512) ack 303 win 61440
00:58.240000 pc532.http-gw > mac.1168: P 2235:2747(512) ack 325 win 17520

more of the same from here, send 3 or 4 packets, timeout, resend 1, send
ack, etc...