In bug 14906 the user complains that the inotify support in nscd
is not sufficient when it comes to detecting changes in the
configurationfiles that should be watched for the various databases.
The current nscd implementation uses inotify to watch for changes in
the configuration files, but adds watches only for IN_DELETE_SELF and
IN_MODIFY. These watches are insufficient to cover even the most basic
uses by a system administrator. For example using emacs or vim to edit
a configuration file should trigger a reload but it might not if
the editors use move to atomically update the file. This atomic update
changes the inode and thus removes the notification on the file (as
inotify is based on inodes). Thus the inotify support in nscd for
configuration files is insufficient to account for the average use
cases of system administrators and users.
The inotify support is significantly enhanced and described here:
https://www.sourceware.org/ml/libc-alpha/2015-02/msg00504.html
Tested on x86_64 with and without inotify support.
This patch avoids warnings for unused results of setuid and setgid in
nscd/connections.c using an ignore_value macro along the lines
suggested by Paul in
<https://sourceware.org/ml/libc-alpha/2014-11/msg00733.html>.
Tested for x86_64.
* include/libc-internal.h (ignore_value): New macro.
* nscd/connections.c (restart): Wrap calls to setuid and setgid
with ignore_value.
Currently, the nscd parent process parses commandline options and
configuration, forks on startup and immediately exits with a success.
If the child process encounters some error after this, it goes
undetected and any services started up after it may have to repeatedly
check to make sure that the nscd service did actually start up and is
serving requests.
To make this process more reliable, I have added a pipe between the
parent and child process, through which the child process sends a
notification to the parent informing it of its status. The parent
waits for this status and once it receives it, exits with the
corresponding exit code. So if the child service sends a success
status (0), the parent exits with a success status. Similarly for
error conditions, the child sends the non-zero status code, which the
parent passes on as the exit code.
This, along with setting the nscd service type to forking in its
systemd configuration file, allows systemd to be certain that the nscd
service is ready and is accepting connections.
We refactor the inotify file checking code and the
database clearing code out of the main_loop_poll and
mail_loop_epoll functions. We document some the related
functions with appropriate comments.
Whenever getaddrinfo needed network interface information it used the
netlink interface to read the information every single time. The
problem is that this information can change at any time.
The patch implements monitoring of the network interfaces through
nscd. If no change is detected the previously read information can
be reused (which is the norm). This timestamp information is also
made available to other processes using the shared memory segment
between nscd and those processes.
nscd can clear caches when certain files change. The list of files
was hardcoded so far and worked for nss_files and nss_dns and those
modules which need no monitoring. nss_db, for instance, has its
own set of files to monitor. Now the NSS modules themselves can
request that certain files are monitored.
2009-02-13 Ulrich Drepper <drepper@redhat.com>
[BZ #5381]
* nscd/nscd.h: Remove definitions and declarations for mem_in_flight.
Change mempool_alloc prototype.
* nscd/mem.c (gc): Don't handle mem_in_flight.
(mempool_alloc): Third parameter now only indicates whether this is the
first call (to allocate data) or not. If it is, get db rdlock.
Release it on error. Don't handle mem_in_flight.
* nscd/aicache.c (addhstaiX): Mark he parameter as const.
Adjust third parameter of mempool_alloc calls.
Nothing to do here in case mempool_alloc fails.
Avoid local variable shadowing parameter. No need to get db rdlock
before calling cache_add.
* nscd/cache.c (cache_add): Adjust call to mempool_alloc. There is
no mem_in_flight array anymore.
* nscd/connections.c: Remove definition and handling of mem_in_flight.
* nscd/grpcache.c (cache_addgr): Adjust third parameter of
mempool_alloc calls. Mark he parameter as const. Nothing to do here
in case mempool_alloc fails. No need to get db rdlock before calling
cache_add.
* nscd/hstcache.c (cache_addhst): Likewise.
* nscd/initgrcache.c (addinitgroupsX): Likewise.
* nscd/servicescache.c (cache_addserv): Likewise.
* nscd/pwdcache.c (cache_addpw): Likewise. Remove some debugging code.
2008-12-03 Petr Baudis <pasky@suse.cz>
[BZ #7067]
* nscd/connections.c (invalidate_cache): Use prune_run_lock
instead of prune_lock.
(nscd_run_prune): Before calling prune_cache, take prune_run_lock.
* nscd/nscd.h (database_dyn): Add prune_run_cache.
__ASSUME_PACCEPT, __ASSUME_IN_NONBLOCK, and __ASSUME_PACCEPT if
appropriate.
* nscd/connections.c: Avoid fcntl calls to set close-on-exec flag and
non-blocking mode by using socket, paccept, and inotify_init1.
fields.
* nscd/connections.c (inotify_fd): New variable.
(nscd_init): Try to open an inotify descriptor.
If successful, watch files for databases using inotify instead of
having prune threads stat the files.
(nscd_run_prune): Recognize clear_cache flag being set and call
prune_cache appropriately.
(main_loop_poll): Add inotify descriptor to wait set and handle the
reported changes.
(main_loop_epoll): Likewise.
* nscd/cache.c (prune_cache): Don't stat files for databases if
inotify is used.
* sysdeps/unix/sysv/linux/Makefile [subdir=nscd]
(CFLAGS-connections.c): Add -DHAVE_INOTIFY.
whether this is in response of a cache refill. Check alignment
of package data. Revamp waking of pruning thread.
(prune_cache): Small optimization.
* nscd/nscd.h: Adjust cache_add prototypes.
* nscd/aicache.c: Adjust cache_add calls.
* nscd/grpcache.c: Likewise.
* nscd/hstcache.c: Likewise.
* nscd/initgrcache.c: Likewise.
* nscd/pwdcache.c: Likewise.
* nscd/servicescache.c: Likewise.
* nscd/connections.c (restart): Really disable cache use before
exec attempt. If it fails, reenable cache.
(nscd_run_prune): Initialize wakeup_time. After wakeup, set wakeup
time to max to be able to notice concurrent cache additions. Unlock
prune_lock while performing gc. Afterwards compute wakeup time with
current wakeup_time value in mind.
2008-04-15 Ulrich Drepper <drepper@redhat.com>
[BZ #5209]
* sysdeps/unix/sysv/linux/times.c: New file.
[BZ #5381]
* nscd/nscd.h: Define enum in_flight, mem_in_flight, and
mem_in_flight_list variables. Add new parameter to mempool_alloc
prototype.
* nscd/mem.c (mempool_alloc): Take additional parameter. Initialize
appropriate mem_in_flight element.
(gc): Take allocations which have not yet been committed to the
database into account.
* nscd/cache.c (cache_add): Add new parameter to mempool_alloc call.
Reset mem_in_flight before returning.
* nscd/connections.c (nscd_run_worker): Initialize mem_in_flight and
cue it up in mem_in_flight_list.
* nscd/aicache.c: Adjust mempool_alloc call.
* nscd/grpcache.c: Likewise.
* nscd/hstcache.c: Likewise.
* nscd/initgrcache.c: Likewise.
* nscd/pwdcache.c: Likewise.
* nscd/servicescache.c: Likewise.
* nscd/Makefile (nscd-flags): Until ld is fixed, use -fpic instead
of -fpie.
* nscd/connections.c (handle_request): Provide better error message
in case SELinux forbids the service.
* version.h (VERSION): Bump to 2.8.90.
* nscd/connections.c (dbs): Add initializers for .suggested_module.
(verify_persistent_db): Remove one unnecessary test and add a new one
for bad configuration.
(nscd_init): Improve error reported when persistent database cannot
be reused.
* nscd/nscd.h (DEFAULT_SUGGESTED_MODULE): Define.
* nscd/nscd_conf.c (nscd_parse_file): Provide default values for
.suggested_module and .max_db_size and case config file says the
values are zero.
* nscd/nscd_helper.c (get_mapping): Fail if hash table module is zero.
* nscd/nscd.h (NSCD_THREAD_STACKSIZE): Define.
* nscd/connections.c (start_threads): Use NSCD_THREAD_STACKSIZE.
* nscd/mem.c (gc): Don't allocate arrays on stack if it can
overflow it.
* sysdeps/unix/sysv/linux/nscd_setup_thread.c (setup_thread):
Return zero in case thread library is not NPTL.
when the lookup call failed.
* nscd/nscd.h (struct database_dyn): Rename prunelock to prune_lock.
Add prune_cond and wakeup_time.
(CACHE_PRUNE_INTERNAL): Define.
Update declarations of prune_cache and setup_thread.
* nscd/connections.c (dbs): Update initializers.
(CACHE_PRUNE_INTERNAL): Moved to nscd.h.
(nscd_init): Default number of threads is now 4.
(invalidate_cache): Take lock before calling prune_cache.
(handle_request): If SELinux forbids the request, say so.
(readylist_cond): Use static initializer.
(nscd_run_prune): New function. Used only by pruning threads.
(nscd_run_worder): Renamed from nscd_run. Remove support for pruning
here.
(fd_ready): Update nscd_run reference.
(start_threads): No need to initialize readylist_cond.
Start pruning threads separately.
* nscd/nscd_setup_thread.c: Change return value type to int and always
return 0.
* sysdeps/unix/sysv/linux/nscd_setup_thread.c: Change return value type
to int and return nonzero value if we can use the TID address hack.
* nscd/cache.c (cache_add): If next wakeup time of cleanup thread for
the database is later than the new entry's timeout, update the
wakeup time and wake the cleanup thread.
(prune_cache): Return seconds the next entry in the database is still
valid. Remove locking for pruning here.
* nscd/nscd.conf: Document default number of threads.
