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author | Volker Lendecke <vl@samba.org> | 2010-03-02 17:02:01 +0100 |
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committer | Volker Lendecke <vl@samba.org> | 2010-03-10 16:07:10 +0100 |
commit | 89c785c47aa0fceba148297116e863f46941bd42 (patch) | |
tree | f1c4812e6467614bd542abda6f8bab198af1889d /source3/include/proto.h | |
parent | 184afeb57d0daeacfacdb8c976032697efe00214 (diff) | |
download | samba-89c785c47aa0fceba148297116e863f46941bd42.tar.gz samba-89c785c47aa0fceba148297116e863f46941bd42.tar.bz2 samba-89c785c47aa0fceba148297116e863f46941bd42.zip |
s3: Fix a long-standing problem with recycled PIDs
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
Diffstat (limited to 'source3/include/proto.h')
-rw-r--r-- | source3/include/proto.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/source3/include/proto.h b/source3/include/proto.h index 7c1f8fa92c..6ecf0a5542 100644 --- a/source3/include/proto.h +++ b/source3/include/proto.h @@ -1205,6 +1205,7 @@ uint32 map_share_mode_to_deny_mode(uint32 share_access, uint32 private_options); pid_t procid_to_pid(const struct server_id *proc); void set_my_vnn(uint32 vnn); uint32 get_my_vnn(void); +void set_my_unique_id(uint64_t unique_id); struct server_id pid_to_procid(pid_t pid); struct server_id procid_self(void); bool procid_equal(const struct server_id *p1, const struct server_id *p2); |