Changeset 359

Timestamp:

Mar 30, 2008, 2:22:48 PM (17 years ago)

Author:

broder

Message:

Added comments and changed to using the syslog module instead of print

Location:

trunk/packages/sipb-xen-console

Files:

• debian/changelog (modified) (1 diff)
• files/usr/bin/sipb-xen-consolefs (modified) (10 diffs)

trunk/packages/sipb-xen-console/debian/changelog

@@ +1 @@
+sipb-xen-console (4) unstable; urgency=low
+
+  * Added comments to sipb-xen-consolefs
+  * Added support for symlinks in the realpath
+  * Changed sipb-xen-consolefs to use syslog instead of printf debugging
+
+ -- SIPB Xen Project <sipb-xen@mit.edu>  Sun, 30 Mar 2008 14:17:59 -0400
+
 sipb-xen-console (3.2) unstable; urgency=low
 

trunk/packages/sipb-xen-console/files/usr/bin/sipb-xen-consolefs

@@ -11 +11 @@
                            # - note: these must be returned as negatives
 
+from syslog import *
+
 import sipb_xen_database
 
@@ -16 +18 @@
 
 realpath = "/home/machines/"
-
-def dirFromList(list):
-        """
-        Return a properly formatted list of items suitable to a directory listing.
-        ['a', 'b', 'c'] => [('a', 0), ('b', 0), ('c', 0)]
-        """
-        return [(x, 0) for x in list]
 
 def getDepth(path):
@@ -40 +35 @@
                 return ['/']
         else:
+                # [1:] because otherwise you get an empty list element from the
+                # initial '/'
                 return path[1:].split('/')
 
@@ -60 +57 @@
 class ConsoleFS(Fuse):
         """
+        ConsoleFS creates a series of subdirectories each mirroring the same real
+        directory, except for a single file - the .k5login - which is dynamically
+        generated for each subdirectory
+        
+        This filesystem only implements the getattr, getdir, read, and readlink
+        calls, beacuse 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
-                print 'Init complete.'
+                
+                openlog('sipb-xen-consolefs ', LOG_PID, LOG_DAEMON)
+                
+                syslog(LOG_DEBUG, 'Init complete.')
         
         def mirrorPath(self, path):
+                """Translate a virtual path to its real path counterpart"""
                 return realpath + "/".join(getParts(path)[1:])
         
         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()
@@ -78 +90 @@
         
         def getUid(self, machine_name):
+                """Calculate the UID of a machine-account, which is just machine_id+1000
+                """
                 return sipb_xen_database.Machine.get_by(name=machine_name).machine_id + 1000
         
         def getK5login(self, machine_name):
+                """Build the ACL for a machine and turn it into a .k5login file
+                """
                 machine = sipb_xen_database.Machine.get_by(name=machine_name)
                 users = [acl.user for acl in machine.acl]
@@ -86 +102 @@
         
         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('@')
@@ -109 +128 @@
                 """
                 
-                print "*** getattr: " + path
+                syslog(LOG_DEBUG, "*** getattr: " + path)
                 
                 depth = getDepth(path)
@@ -115 +134 @@
                 
                 st = MyStat()
+                # / is a directory
                 if path == '/':
                         st.st_mode = stat.S_IFDIR | 0755
                         st.st_nlink = 2
+                # /foo is a directory if foo is a machine - otherwise it doesn't exist
                 elif depth == 1:
                         if parts[-1] in self.getMachines():
                                 st.st_mode = stat.S_IFDIR | 0755
                                 st.st_nlink = 2
+                                # Homedirs should be owned by the user whose homedir it is
                                 st.st_uid = st.st_gid = self.getUid(parts[0])
                         else:
                                 return -errno.ENOENT
+                # Catch the .k5login file, because it's a special case
                 elif depth == 2 and parts[-1] == '.k5login':
                         st.st_mode = stat.S_IFREG | 0444
                         st.st_nlink = 1
                         st.st_size = len(self.getK5login(parts[0]))
+                        # The .k5login file should be owned by the user whose homedir it is
                         st.st_uid = st.st_gid = self.getUid(parts[0])
+                # For anything else, we get the mirror path and call out to the OS
                 else:
                         stats = list(os.lstat(self.mirrorPath(path)))
+                        # Shadow the UID and GID from the original homedir
                         stats[4:6] = [self.getUid(parts[0])] * 2
                         return tuple(stats)
                 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):
-                print '*** readdir', 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):
-                print '*** getdir', 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)
+                
+                # '/' contains a directory for each machine
                 if path == '/':
-                        contents = ['.', '..']+self.getMachines()
+                        contents = self.getMachines()
+                # The directory for each machine contains the same files as the realpath
+                # but also the .k5login
+                #
+                # The list is converted to a set so that we can handle the case where 
+                # there is already a .k5login in the realpath gracefully
                 elif getDepth(path) == 1:
-                        contents = set(os.listdir(self.mirrorPath(path)) + ['.k5login', '.', '..'])
-                else:
-                        contents = os.listdir(self.mirrorPath(path)) + ['.', '..']
-                return [(i, 0) for i in contents]
-        
-        def read ( self, path, length, offset ):
-                print '*** read', path, length, offset
+                        contents = set(os.listdir(self.mirrorPath(path)) + ['.k5login'])
+                # If it's not the root of the homedir, just pass the call onto the OS
+                # for realpath
+                else:
+                        contents = os.listdir(self.mirrorPath(path))
+                # 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 = getParts(path)
                 
+                # If the depth is less than 2, then either it's a directory or the file
+                # doesn't exist
+                # (realistically this doesn't appear to ever happen)
                 if getDepth(path) < 2:
                         return -errno.ENOENT
+                # If we're asking for a real .k5login file, then create it and return
+                # the snippet requested
                 elif parts[1:] == ['.k5login']:
                         if parts[0] not in self.getMachines():
@@ -163 +217 @@
                         else:
                                 return self.getK5login(parts[0])[offset:length + offset]
+                # Otherwise, pass the call onto the OS
+                # (note that the file will get closed when this call returns and the
+                # file descriptor goes out of scope)
                 else:
                         fname = self.mirrorPath(path)
@@ -171 +228 @@
                                 f.seek(offset)
                                 return f.read(length)
+        
+        def readlink(self, path):
+                syslog(LOG_DEBUG, '*** readlink %s' % path)
+                
+                # There aren't any symlinks here
+                if getDepth(path) < 2:
+                        return -errno.ENOENT
+                # But there might be here
+                else:
+                        return os.readlink(self.mirrorPath(path))
 
 if __name__ == '__main__':