Functionality for clearing the nscd cache in pynslcd

2 files changed, 108 insertions, 1 deletions

diff --git a/pynslcd/Makefile.am b/pynslcd/Makefile.am
index cff5629..6203d12 100644
--- a/pynslcd/Makefile.am
+++ b/pynslcd/Makefile.am
@@ -20,7 +20,7 @@
 pynslcddir = $(datadir)/pynslcd
 
 pynslcd_PYTHON = pynslcd.py attmap.py cache.py cfg.py common.py expr.py \
-                 mypidfile.py search.py tio.py \
+                 mypidfile.py nscd.py search.py tio.py \
                  alias.py ether.py group.py host.py netgroup.py network.py \
                  pam.py passwd.py protocol.py rpc.py service.py shadow.py
 nodist_pynslcd_PYTHON = constants.py
diff --git a/pynslcd/nscd.py b/pynslcd/nscd.py
new file mode 100644
index 0000000..89cb483
--- /dev/null
+++ b/pynslcd/nscd.py
@@ -0,0 +1,107 @@
+
+# nscd.py - functions for invalidating the nscd cache
+#
+# Copyright (C) 2013 Arthur de Jong
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301 USA
+
+import fcntl
+import logging
+import os
+import subprocess
+import struct
+
+
+# the file descriptor used for sending messages to the child process
+signalfd = None
+
+
+# mapping between map name and signal character
+_db_to_char = dict(
+        aliases='A', ethers='E', group='G', hosts='H', netgroup='U',
+        networks='N', passwd='P', protocols='L', rpc='R', services='V',
+        shadow='S',
+    )
+_char_to_db = dict((reversed(item) for item in _db_to_char.items()))
+
+
+def exec_invalidate(db):
+    logging.debug('nscd_invalidator: nscd -i %s', db)
+    try:
+        p = subprocess.Popen(['nscd', '-i', 'passwd'],
+                             bufsize=4096, close_fds=True,
+                             stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+        output, ignored = p.communicate()
+        if output:
+            output = ': %s' % output[:1024].strip()
+        if p.returncode == 0:
+            logging.debug('nscd_invalidator: nscd -i %s (pid %d) success%s',
+                          db, p.pid, output)
+        elif p.returncode > 0:
+            logging.debug('nscd_invalidator: nscd -i %s (pid %d) failed (%d)%s',
+                          db, p.pid, p.returncode, output)
+        else:  # p.returncode < 0
+            logging.error('nscd_invalidator: nscd -i %s (pid %d) killed by signal %d%s',
+                          db, p.pid, -p.returncode, output)
+    except:
+        logging.warn('nscd_invalidator: nscd -i %s failed', db, exc_info=True)
+
+
+def loop(fd):
+    # set process title
+    try:
+        import setproctitle
+        setproctitle.setproctitle('(nscd invalidator)')
+    except ImportError:
+        pass
+    # set up clean environment
+    os.chdir('/')
+    os.environ['PATH'] = '/usr/sbin:/usr/bin:/sbin:/bin'
+    while True:
+        db = os.read(fd, 1)
+        # FIXME: define the characters and maps somewhere
+        if db == '':
+            break
+        db = _char_to_db.get(db, None)
+        if db:
+            exec_invalidate(db)
+
+
+def start_invalidator():
+    r, w = os.pipe()
+    # mark write end as non-blocking
+    flags = fcntl.fcntl(w, fcntl.F_GETFL)
+    fcntl.fcntl(w, fcntl.F_SETFL, flags | os.O_NONBLOCK)
+    cpid = os.fork()
+    if cpid == 0:
+        # we are the child
+        os.close(w)
+        loop(r)
+        os._exit(1)
+    # we are the parent
+    global signalfd
+    signalfd = w
+    os.close(r)
+
+
+def invalidate(db=None):
+    if signalfd is None:
+        return  # nothing to do
+    db = _db_to_char.get(db, '')
+    try:
+        os.write(signalfd, db)
+    except:
+        logging.warn('nscd_invalidator: nscd -i %s failed', db, exc_info=True)