This is really really interesting.
When sending a job to a printer, the LPD server will:
a) open a connection (FD = xxx)
b) fork a server process to be the filter
c) dup the connection FD = xxx to be STDOUT (FD = 1)
d) exec the filter
e) wait for filter to complete
f) repeat b,c,d,e until all files are sent
Now here is the neat part. If the connection is a socket
AND the filter puts the socket in NONBLOCKING mode
THEN all operations by other processes become nonblocking.
... This depends
a) OS
b) VERSION of OS
c) Type of connection (socket/io device)
Now it turns out that some OS's implement pipes as (effectively)
sockets, and some as 'real devices'. So this means that STRANGE
things can happen. Cool... And there is virtually no way that
you can determine the particuar behavour using configure without
writing TCMFH (The Configure Macro From Hell).
In the next/latest release of LPRng the LPD server will
reset ALL passed FD's to filters into NONBLOCKING mode
and then when the subprocesses exit, reset them to NONBLOCKING
mode. This seems to solve the problem of the mystery
'run away process'.
Thanks to the folks at BSDCON 2002 who thought about this
and suggested a possible cause of the problem.
Patrick Powell Astart Technologies,
[EMAIL PROTECTED] 9475 Chesapeake Drive, Suite D,
Network and System San Diego, CA 92123
Consulting 858-874-6543 FAX 858-279-8424
LPRng - Print Spooler (http://www.lprng.com)
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