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Trying to trim down messages.c a bit: Sending to all processes that are
registered in serverid.tdb and filtering to me is not really logic of general
messaging but more of the serverid code.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
The only reason for this complex monster was an overload of ctdbd.
When opening files, we unconditionally checked all share modes for
validity. This meant thousands of serverid_exists calls per second
for popular directories. This has long gone, now we only check for
validity if a conflict happens.
The only remaining caller is net serverid wipedbs, an administrative
command. If that loads ctdbd, so be it.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
This started per https://bugzilla.samba.org/show_bug.cgi?id=8872#c4
and avoids any possible collision with a different process.
We also need to ensure that across a Samba installation on a single
node that id.vnn is the same. Samba4 previously used 0, while Samba3
used NONCLUSTER_VNN. When a message is sent between these 'different'
nodes, the error NT_STATUS_INVALID_DEVICE_REQUEST is raised.
Andrew Bartlett
In the child, we fully re-open serverid.tdb, which leads to one fcntl lock for
CLEAR_IF_FIRST detection per smbd. This opens the tdb in the parent and holds
it, so that tdb_reopen_all correctly catches the CLEAR_IF_FIRST bit.
When a samba server process dies hard, it has no chance to clean up its entries
in locking.tdb, brlock.tdb, connections.tdb and sessionid.tdb.
For locking.tdb and brlock.tdb Samba is robust by checking every time we read
an entry from the database if the corresponding process still exists. If it
does not exist anymore, the entry is deleted. This is not 100% failsafe though:
On systems with a limited PID space there is a non-zero chance that between the
smbd's death and the fresh access, the PID is recycled by another long-running
process. This renders all files that had been locked by the killed smbd
potentially unusable until the new process also dies.
This patch is supposed to fix the problem the following way: Every process ID
in every database is augmented by a random 64-bit number that is stored in a
serverid.tdb. Whenever we need to check if a process still exists we know its
PID and the 64-bit number. We look up the PID in serverid.tdb and compare the
64-bit number. If it's the same, the process still is a valid smbd holding the
lock. If it is different, a new smbd has taken over.
I believe this is safe against an smbd that has died hard and the PID has been
taken over by a non-samba process. This process would not have registered
itself with a fresh 64-bit number in serverid.tdb, so the old one still exists
in serverid.tdb. We protect against this case by the parent smbd taking care of
deregistering PIDs from serverid.tdb and the fact that serverid.tdb is
CLEAR_IF_FIRST.
CLEAR_IF_FIRST does not work in a cluster, so the automatic cleanup does not
work when all smbds are restarted. For this, "net serverid wipe" has to be run
before smbd starts up. As a convenience, "net serverid wipedbs" also cleans up
sessionid.tdb and connections.tdb.
While there, this also cleans up overloading connections.tdb with all the
process entries just for messaging_send_all().
Volker
