lib: Add messaging_dgm

Messaging based on unix domain datagram sockets

This makes every process participating in messaging bind on a unix domain
datagram socket, similar to the source4 based messaging. The details are a bit
different though:

Retry after EWOULDBLOCK is done with a blocking thread, not by polling. This
was the only way I could in experiments avoid a thundering herd or high load
under Linux in extreme overload situations like many thousands of processes
sending to one blocked process. If there are better ideas to do this in a
simple way, I'm more than happy to remove the pthreadpool dependency again.

There is only one socket per process, not per task. I don't think that per-task
sockets are really necessary, we can do filtering in user space. The message
contains the destination server_id, which contains the destination task_id. I
think we can rebase the source4 based imessaging on top of this, allowing
multiple imessaging contexts on top of one messaging_context. I had planned to
do this conversion before this goes in, but Jeremy convinced me that this has
value in itself :-)

Per socket we also create a fcntl-based lockfile to allow race-free cleanup of
orphaned sockets. This lockfile contains the unique_id, which in the future
will make the server_id.tdb obsolete.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/source3/smbd/server.c b/source3/smbd/server.c
index 96580ba4e2e..5ff370d1edb 100644
--- a/source3/smbd/server.c
+++ b/source3/smbd/server.c
@@ -465,6 +465,8 @@ static void remove_child_pid(struct smbd_parent_context *parent,
 	}
 
 	if (unclean_shutdown) {
+		NTSTATUS status;
+
 		/* a child terminated uncleanly so tickle all
 		   processes to see if they can grab any of the
 		   pending locks
@@ -488,6 +490,10 @@ static void remove_child_pid(struct smbd_parent_context *parent,
 		 * terminated uncleanly.
 		 */
 		messaging_cleanup_server(parent->msg_ctx, child_id);
+
+		status = messaging_dgm_cleanup(parent->msg_ctx, pid);
+		DEBUG(10, ("%s: messaging_dgm_cleanup returned %s\n",
+			   __func__, nt_errstr(status)));
 	}
 
 	if (!serverid_deregister(child_id)) {