source: branches/wsgi/packages/sipb-xen-remote-server/files/usr/sbin/sipb-xen-remconffs @ 981

#!/usr/bin/python

import fuse
from fuse import Fuse

from time import time

import stat     # for file properties
import os         # for filesystem modes (O_RDONLY, etc)
import errno   # for error number codes (ENOENT, etc)
                           # - note: these must be returned as negatives

from syslog import *

import sipb_xen_database

fuse.fuse_python_api = (0, 2)

def getDepth(path):
        """
        Return the depth of a given path, zero-based from root ('/')
        """
        if path == '/':
                return 0
        else:
                return path.count('/')

def getParts(path):
        """
        Return the slash-separated parts of a given path as a list
        """
        # [1:] to exclude leading empty element
        split = path.split('/')
        if split[-1]:
                return split[1:]
        else:
                return split[1:-1]

def parse(path):
        parts = getParts(path)
        return parts, len(parts)

class MyStat:
        def __init__(self):
                self.st_mode = 0
                self.st_ino = 0
                self.st_dev = 0
                self.st_nlink = 0
                self.st_uid = 0
                self.st_gid = 0
                self.st_size = 0
                self.st_atime = 0
                self.st_mtime = 0
                self.st_ctime = 0
        
        def toTuple(self):
                return (self.st_mode, self.st_ino, self.st_dev, self.st_nlink, self.st_uid, self.st_gid, self.st_size, self.st_atime, self.st_mtime, self.st_ctime)

class RemConfFS(Fuse):
        """
        RemConfFS creates a filesytem for configuring remctl, like this:
        /
        |-- acl
        |   |-- machine1
        |   ...
        |   `-- machinen
        `-- conf.d
            |-- machine1
            ...
            `-- machinen

        The machine list and the acls are drawn from a database.
        
        This filesystem only implements the getattr, getdir, read, and readlink
        calls, because this is a read-only filesystem.
        """
        
        def __init__(self, *args, **kw):
                """Initialize the filesystem and set it to allow_other access besides
                the user who mounts the filesystem (i.e. root)
                """
                Fuse.__init__(self, *args, **kw)
                self.lasttime = time()
                self.allow_other = 1
                
                openlog('sipb-xen-remconffs ', LOG_PID, LOG_DAEMON)
                
                syslog(LOG_DEBUG, 'Init complete.')

        def getMachines(self):
                """Get the list of VMs in the database, clearing the cache if it's 
                older than 15 seconds"""
                if time() - self.lasttime > 15:
                        self.lasttime = time()
                        sipb_xen_database.clear_cache()
                return [machine.name for machine in sipb_xen_database.Machine.select()]
                
        def getacl(self, machine_name):
                """Build the ACL file for a machine
                """
                machine = sipb_xen_database.Machine.get_by(name=machine_name)
                users = [acl.user for acl in machine.acl]
                return "\n".join(map(self.userToPrinc, users)
                                 + ['include /etc/remctl/acl/web',
                                    ''])
                
        def getconf(self):
                """Build the master conf file, with all machines
                """
                return '\n'.join("control %s /usr/sbin/sipb-xen-remote-proxy-control"
                                 " /etc/remctl/remconffs/acl/%s"
                                 % (machine_name, machine_name)
                                 for machine_name in self.getMachines())+'\n'
        
        def userToPrinc(self, user):
                """Convert Kerberos v4-style names to v5-style and append a default
                realm if none is specified
                """
                if '@' in user:
                        (princ, realm) = user.split('@')
                else:
                        princ = user
                        realm = "ATHENA.MIT.EDU"
                
                return princ.replace('.', '/') + '@' + realm
        
        def getattr(self, path):
                """
                - st_mode (protection bits)
                - st_ino (inode number)
                - st_dev (device)
                - st_nlink (number of hard links)
                - st_uid (user ID of owner)
                - st_gid (group ID of owner)
                - st_size (size of file, in bytes)
                - st_atime (time of most recent access)
                - st_mtime (time of most recent content modification)
                - st_ctime (platform dependent; time of most recent metadata change on Unix,
                                        or the time of creation on Windows).
                """
                
                syslog(LOG_DEBUG, "*** getattr: " + path)
                
                depth = getDepth(path)
                parts = getParts(path)
                
                st = MyStat()
                if path == '/':
                        st.st_mode = stat.S_IFDIR | 0755
                        st.st_nlink = 2
                elif depth == 1:
                        if parts[0] == 'acl':
                                st.st_mode = stat.S_IFDIR | 0755
                                st.st_nlink = 2
                        elif parts[0] == 'conf':
                                st.st_mode = stat.S_IFREG | 0444
                                st.st_nlink = 1
                                st.st_size = len(self.getconf())
                        else:
                                return -errno.ENOENT
                elif depth == 2:
                        if parts[0] != 'acl':
                                return -errno.ENOENT
                        if parts[1] not in self.getMachines():
                                return -errno.ENOENT
                        st.st_mode = stat.S_IFREG | 0444
                        st.st_nlink = 1
                        st.st_size = len(self.getacl(parts[1]))

                return st.toTuple()
        
        # This call isn't actually used in the version of Fuse on console, but we
        # wanted to leave it implemented to ease the transition in the future
        def readdir(self, path, offset):
                """Return a generator with the listing for a directory
                """
                syslog(LOG_DEBUG, '*** readdir %s %s' % (path, offset))
                for (value, zero) in self.getdir(path):
                        yield fuse.Direntry(value)
        
        def getdir(self, path):
                """Return a list of tuples of the form (item, 0) with the contents of
                the directory path
                
                Fuse doesn't add '.' or '..' on its own, so we have to
                """
                syslog(LOG_DEBUG, '*** getdir %s' % path)
                
                parts, depth = parse(path)

                if depth == 0:
                        contents = ('acl', 'conf')
                elif depth == 1:
                        if parts[0] == 'acl':
                                contents = self.getMachines()
                        else:
                                return -errno.ENOENT
                else:
                        return -errno.ENOTDIR

                # Format the list the way that Fuse wants it - and don't forget to add
                # '.' and '..'
                return [(i, 0) for i in (list(contents) + ['.', '..'])]

        def read(self, path, length, offset):
                """Read length bytes starting at offset of path. In most cases, this
                just gets passed on to the OS
                """
                syslog(LOG_DEBUG, '*** read %s %s %s' % (path, length, offset))
                
                parts, depth = parse(path)
                
                if depth == 0:
                        return -errno.EISDIR
                elif parts[0] == 'conf':
                        return self.getconf()[offset:offset+length]
                elif parts[0] == 'acl':
                        if depth == 1:
                                return -errno.EISDIR
                        if parts[1] in self.getMachines():
                                return self.getacl(parts[1])[offset:offset+length]
                return -errno.ENOENT
        
        def readlink(self, path):
                syslog(LOG_DEBUG, '*** readlink %s' % path)
                return -errno.ENOENT


if __name__ == '__main__':
        sipb_xen_database.connect('postgres://sipb-xen@sipb-xen-dev.mit.edu/sipb_xen')
        usage="""
$0 [mount_path]
"""
        server = RemConfFS()
        server.flags = 0
        server.main()