lost blocks in TCP/IP streams

[forsyth@plan9.cs.york.ac.uk forsyth@plan9.cs.york.ac.uk]

I have recently tracked down some troublesome kernel
memory leaks, that turned out to be mainly in the TCP/IP subsystem.
While doing so, I found several off-by-one allocation errors that
might lead to kernel heap corruption and subsequent panics.

I'm not sure how worthwhile it is sending the changes out if a new release is
imminent, but the consequences of the various small errors are annoying enough
that you might not like to wait even a month or so.  Specifically, if
you have a machine that receives or sends moderate to heavy TCP/IP traffic, chances
are that your kernel will gradually/rapidly run out of kernel memory, since it
fails to free stream Blocks at several key points.  A busy but small machine (one of my 16 Mbyte PCs),
has run out of memory in under two days.  Very tedious!
On the other hand, I run several other machines that haven't been
troubled anything like so much; it depends on the nature of the traffic.

Anyhow, if you are interested in receiving the changes, please let me know by
email.

If you have a >1.02 Gbyte SCSI disc, also let me know and I can supply
changes to the port SCSI code to use extended read/write requests when necessary.

Finally, here is an one line change to /sys/src/9/pc/main.c to stop reads of /dev/sysstat
from mangling memory and eventually crashing the system (386/486 only).  Insert the following
line as the first executable statement of confinit():
	conf.nmach = 1;
Without it, conf.nmach is zero.