This is only indirectly related to Exim, but I wondered if anyone on
this list is expert enough to comment on the following problem:
Running "netstat" on machine A shows a connection from port 25 on that
machine to some other port on machine B. However, there are no longer
any mail processes running on machine A, and "netstat" on machine B does
not show this connection. The state of the connection is given as
"CLOSE_WAIT", and it sits there for days and days. While it is present,
attempts to restart a mail listener on machine A fail, saying "port
already in use". Machine A is running Solaris 2.4/101945-37 and by
coincidence, one of several machine Bs involved is running the same OS,
though I don't believe this is relevant.
Additional circumstatial information:
The mail listener that was originally running on machine A (Exim) *did*
set the SO_REUSEADDR option on its socket. This is known to work when
existing connections are in states other than CLOSE_WAIT.
A similar problem has been seen on our printer spooling machine, this
time involving the lpr printer port rather than the SMTP port. I don't
think the particular port is relevant.
The phenonenon seems to be correlated with periods of heavy load, during
which it is presumed that SMTP connection requests to machine A might
have failed. The backlog parameter given in the "listen" function was 5.
Incidentally, the manual says that when these 5 queue slots are full,
additional connections are refused, but in fact they time out. While
investigating this case on another system, I once saw a transient
connection in netstat that had port number 1023 (privileged) and
TIME_WAIT, but I couldn't reproduce that; presumably it is short-lived.
After several days of trying, I have failed to find a way of provoking
CLOSE_WAIT connections in the absence of a process with an open socket.
Does anyone know if there is any way of forcing these phantom
connections to go away, short of rebooting the machine? Preferably short
of shutting down and restarting the network interface as well!
Philip
--
Philip Hazel University Computing Service,
ph10@??? New Museums Site, Cambridge CB2 3QG,
P.Hazel@??? England. Phone: +44 1223 334714
