Fix a descriptor leak in devd. Clients reading /var/run/devd.pipe can close

their socket connection any time, and devd only notices that when it gets an
error trying to write an event to the client.  On a system with no device
change activity, clients could connect and disappear repeatedly without devd
noticing, leading to an ever-growing list of open socket descriptors in devd.

Now devd uses poll(2) looking for POLLHUP on all existing clients every time
a new client connection is established, and also periodically (once a minute)
to proactively find zombie clients and reap the socket descriptors.  It also
now has a connection limit, configurable with a new -l <num> command line arg.
When the maximum number of connections is reached it stops accepting new
connections until some current clients drop off.

Reviewed by:	imp
Approved by:	cognet (mentor)

1 files changed, 7 insertions, 0 deletions

diff --git a/sbin/devd/devd.8 b/sbin/devd/devd.8
index 7377e25..bc5092c 100644
--- a/sbin/devd/devd.8
+++ b/sbin/devd/devd.8
@@ -35,6 +35,7 @@
 .Nm
 .Op Fl Ddn
 .Op Fl f Ar file
+.Op Fl l Ar num
 .Sh DESCRIPTION
 The
 .Nm
@@ -55,6 +56,12 @@ instead of the default
 If option
 .Fl f
 is specified more than once, the last file specified is used.
+.It Fl l Ar num
+Limit concurrent
+.Pa /var/run/devd.pipe
+connections to
+.Ar num .
+The default connection limit is 10.
 .It Fl n
 Do not process all pending events before becoming a daemon.
 Instead, call daemon right away.