Prototype implementation of bind mounts.

examples/bind.py

@@ -0,0 +1,164 @@
+#!/usr/bin/python
+
+"""
+bind.py: Bind mount prototype
+
+This creates hosts with private directories as desired.
+"""
+
+from mininet.net import Mininet
+from mininet.node import Host, Switch, Controller
+from mininet.cli import CLI
+from mininet.util import errFail, quietRun, errRun
+from mininet.topo import SingleSwitchTopo
+from mininet.log import setLogLevel, info, debug
+
+from os.path import join, realpath
+from functools import partial
+
+# Utility functions for unmounting a tree
+
+def mountPoints():
+    "Return list of mounted file systems"
+    mtab, _err, _ret = errFail( 'cat /proc/mounts' )
+    lines = mtab.split( '\n' )
+    mounts = []
+    for line in lines:
+        if not line:
+            continue
+        fields = line.split( ' ')
+        mount = fields[ 1 ]
+        mounts.append( mount )
+    return mounts
+
+def unmountAll( dir='/var/run/mn' ):
+    "Unmount all mounts under a directory tree"
+    dir = realpath( dir )
+    # Find all mounts below dir
+    # This is subtle because /foo is not
+    # a parent of /foot
+    dirslash = dir + '/'
+    mounts = [ m for m in mountPoints()
+              if m == dir or m.find( dirslash ) == 0 ]
+    # Unmount them from bottom to top
+    mounts.sort( reverse=True )
+    for mount in mounts:
+        debug( 'Unmounting', mount, '\n' )
+        out, err, code = errRun( 'umount', mount )
+        if code != 0:
+            info( '*** Warning: failed to umount', mount, '\n' )
+            info( err )
+
+
+class HostWithPrivateDirs( Host ):
+    "Host with private directories"
+
+    mnRunDir = realpath( '/var/run/mn' )
+
+    def __init__(self, name, *args, **kwargs ):
+        "privateDirs: list of private directories"
+        self.privateDirs = kwargs.pop( 'privateDirs', [] )
+        Host.__init__( self, name, *args, **kwargs )
+        self.rundir = '%s/%s' % ( self.mnRunDir, name )
+        if self.privateDirs:
+            self.privateDirs = [ realpath( d ) for d in self.privateDirs ]
+            self.createBindMounts()
+        # These should run in the namespace before we chroot,
+        # in order to put the right entries in /etc/mtab
+        # Eventually this will allow a local pid space
+        # Now we chroot and cd to wherever we were before.
+        pwd = self.cmd( 'pwd' ).strip()
+        self.sendCmd( 'exec chroot', self.root, 'bash -ms mininet:'
+                       + self.name )
+        self.waiting = False
+        self.cmd( 'cd', pwd )
+        # In order for many utilities to work,
+        # we need to remount /proc and /sys
+        self.cmd( 'mount /proc' )
+        self.cmd( 'mount /sys' )
+
+    def mountPrivateDirs( self ):
+        "Create and bind mount private dirs"
+        for dir in self.privateDirs:
+            privateDir = self.private + dir
+            errFail( 'mkdir -p ' + privateDir )
+            mountPoint = self.root + dir
+            errFail( 'mount -B %s %s' %
+                           ( privateDir, mountPoint) )
+
+    def remountDirs( self, fstypes=[ 'nfs' ] ):
+        "Remount mounted file systems"
+        dirs = self.cmd( 'cat /proc/mounts' ).strip().split( '\n' )
+        for dir in dirs:
+            line = dir.split()
+            mountpoint, fstype = line[ 1 ], line[ 2 ]
+            # Don't re-remount directories!!!
+            if mountpoint.find( self.mnRunDir ) == 0:
+                continue
+            if fstype in fstypes:
+                print "remounting:", mountpoint
+                errFail( 'mount -B %s %s' % (
+                         mountpoint, self.root + mountpoint ) )
+
+    def createBindMounts( self ):
+        """Create a chroot directory structure,
+           with self.privateDirs as private dirs"""
+        errFail( 'mkdir -p '+ self.rundir )
+        unmountAll( self.rundir )
+        # Create /root and /private directories
+        self.root = self.rundir + '/root'
+        self.private = self.rundir + '/private'
+        errFail( 'mkdir -p ' + self.root )
+        errFail( 'mkdir -p ' + self.private )
+        # Recursively mount / in private doort
+        # note we'll remount /sys and /proc later
+        errFail( 'mount -B / ' + self.root )
+        self.remountDirs()
+        self.mountPrivateDirs()
+
+    def unmountBindMounts( self ):
+        "Unmount all of our bind mounts"
+        unmountAll( self.rundir )
+
+    def popen( self, *args, **kwargs ):
+        "Popen with chroot support"
+        chroot = kwargs.pop( 'chroot', True )
+        mncmd = kwargs.get( 'mncmd',
+                           [ 'mnexec', '-a', str( self.pid ) ] )
+        if chroot:
+            mncmd = [ 'chroot', self.root ] + mncmd
+            kwargs[ 'mncmd' ] = mncmd
+        return Host.popen( self, *args, **kwargs )
+
+    def cleanup( self ):
+        "Clean up, then unmount bind mounts"
+        # Wait for process to actually terminate
+        self.shell.wait()
+        Host.cleanup( self )
+        self.unmountBindMounts()
+        errFail( 'rmdir ' + self.root )
+
+# Sample usage
+
+def testHostWithPrivateDirs():
+    "Test bind mounts"
+    topo = SingleSwitchTopo( 2 )
+    privateDirs = [ '/var/log', '/var/run' ]
+    host = partial( HostWithPrivateDirs, privateDirs=privateDirs )
+    net = Mininet( topo=topo, host=host )
+    net.start()
+    print 'Private Directories:', privateDirs
+    CLI( net )
+    net.stop()
+
+
+if __name__ == '__main__':
+    unmountAll()
+    setLogLevel( 'info' )
+    testHostWithPrivateDirs()
+    unmountAll()
+
+
+
+
+