| From peter.bentley@nomura.co.uk Fri Jun 19 10:01:21 1998

| Ken Wellsch wrote:
| > | On Jun 18, Ken Wellsch wrote
| > | > Within what seems like a few seconds I've consumed all my mbuf space,
| > | > crippling my server system.  netstat claims I've got the expected 16Kb
| > | > in the queue.
| > | >
| > | > The same server to another system, e.g. W95, W/NT, Linux does not have
| > | > this problem - the NetBSD seems to be properly blocking my writes.
| 
| Have you been able to verify (eg with truss) that your writes are being
| blocked? I know that the 16K in the send queue points to that, but if
| the data consuming the mbufs isn't coming from your app, and if the Mac
| isn't sending data to you then it must be triggering some very odd
| breakage inside the TCP stack, perhaps by advertising dumb window sizes.
| 
| > I have watched via "netstat -m" as the percent used number grows
| > rapidly when I'm running my application.  I mean rapidly too.  I
| > ran "netstat" as quickly as I could and the %-used increased something
| > like 6% to start, 23%, 56%, 73% and that is when I killed the process.
| 
| Perhaps if you could capture the start of the TCP stream with tcpdump,
| one of the TCP gooroos can spot what the problem is...

Here is what I hope is useful info (I notice the large ttl value first-off).
I notice I've got a fair number of mbuf's in use now, but I've not run out.

("mac" is a Mac 6400 running MacOS 8.0 and "link" is a large i386/NetBSD box)

11:40:00.452641 mac.link-systems.com.2177 > link.link-systems.com.1234: P 168:169(1) ack 1 win 0 (DF) (ttl 255, id 1614)
11:40:00.452698 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 169 win 17287 (ttl 64, id 43601)
11:40:00.453261 mac.link-systems.com.2177 > link.link-systems.com.1234: P 169:170(1) ack 1 win 0 (DF) (ttl 255, id 1615)
11:40:00.453320 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 170 win 17286 (ttl 64, id 43602)
11:40:00.453872 mac.link-systems.com.2177 > link.link-systems.com.1234: P 170:171(1) ack 1 win 0 (DF) (ttl 255, id 1616)
11:40:00.453930 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 171 win 17285 (ttl 64, id 43603)
11:40:00.454481 mac.link-systems.com.2177 > link.link-systems.com.1234: P 171:172(1) ack 1 win 0 (DF) (ttl 255, id 1617)
11:40:00.454538 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 172 win 17284 (ttl 64, id 43604)
11:40:00.455089 mac.link-systems.com.2177 > link.link-systems.com.1234: P 172:173(1) ack 1 win 0 (DF) (ttl 255, id 1618)
11:40:00.455147 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 173 win 17283 (ttl 64, id 43605)
11:40:00.455698 mac.link-systems.com.2177 > link.link-systems.com.1234: P 173:174(1) ack 1 win 0 (DF) (ttl 255, id 1619)
11:40:00.455757 link.link-systems.com.1234 > mac.link-systems.com.2177: . ack 174 win 17282 (ttl 64, id 43606)