#!/usr/bin/python2
# VSYS script to configure routes on virtual network interfaces from the root slice
#   Claudio Freire - 2011/05/19
#
# Gets slice name as argv[1]
# Takes routing rules on stdin, one per line
#   rule := command ' ' target ' gw ' host device
#   command := 'add' | 'del'
#   target := host | network
#   network := host [ '/' netmask ]
#   netmask := number
#   host := number '.' number '.' number '.' number
#   number := [0-9]+
#   device := ( tun | tap ) slice '-' number
#   slice := <slice id>
#
# All networks and gateways MUST belong to the virtual
# network assigned to the slice (according to the vsys_vnet tag)
#
# Examples:
#
#   add 10.0.0.0/24 gw 10.0.0.1 tap754-0
#   del 10.0.0.0/24 gw 10.0.0.1 tap754-0
#


import sys
import pwd
import re
import socket
import struct
import os
import string
import subprocess

vsys_config_dir = "/etc/planetlab/vsys-attributes"

if len(sys.argv) != 2: sys.exit(1)

# VSYS scripts get slicename as $1
slicename=sys.argv[1]
sliceid = pwd.getpwnam(slicename).pw_uid

netblock_config=os.path.join(vsys_config_dir,slicename,"vsys_vnet")

# Read netblock allocation file
vnet_base = None
vnet_mask = None

try:
    for netblock in open(netblock_config,'r'):
        vnet_base, vnet_mask = netblock.split('/')
        vnet_mask = int(vnet_mask)
except:
    vnet_base = vnet_mask = None

if vnet_base is None:
    print >>sys.stderr, "Could not find entry for slice %s in netblock config file %s" % (slicename, netblock_config)
    sys.exit(1)

vnet_int = struct.unpack('!L', socket.inet_aton(vnet_base))[0]
vnet_int = (vnet_int >> (32-vnet_mask)) << (32-vnet_mask)
mask_int = (0xffffffff >> (32-vnet_mask)) << (32-vnet_mask)

# rule line regex
rule_re = r"(?P<cmd>add|del)\s+(?P<targetbase>(?:\d{1,3}[.]){3}\d{1,3})(?:/(?P<targetprefix>\d{1,2}))?\s+gw\s+(?P<gw>(?:\d{1,3}[.]){3}\d{1,3}) (?P<dev>(?:tun|tap)%d-\d{1,5})" % (sliceid,)
rule_re = re.compile(rule_re)

### Read args from stdin
for argline in sys.stdin:
    argline = argline.strip()
    
    # Match rule against the regex, 
    # validating overall structure in the process
    match = rule_re.match(argline)
    if not match:
        print >>sys.stderr, "Invalid rule %r" % (argline,)
        continue
    
    # Validate IPs involved
    try:
        target_ip_int = struct.unpack('!L',
            socket.inet_aton(match.group('targetbase')))[0]
    except Exception,e:
        print >>sys.stderr, "Invalid target ip: %s" % (e,)
        continue

    try:
        gw_ip_int = struct.unpack('!L',
            socket.inet_aton(match.group('gw')))[0]
    except Exception,e:
        print >>sys.stderr, "Invalid target ip: %s" % (e,)
        continue

    if match.group('targetprefix'):
        try:
            target_mask = int(match.group('targetprefix'))
        except Exception,e:
            print >>sys.stderr, "Invalid target mask: %s" % (e,)
            continue
    else:
        # host route
        target_mask = 32
    
    ifname = match.group('dev')
    if not ifname:
        # Shouldn't happen, but just in case
        print >>sys.stderr, "Invalid rule %r: Unspecified interface" % (argline,)
        continue
    
    # Make sure all IPs/networks fall within the assigne vnet
    if target_mask < vnet_mask:
        print >>sys.stderr, "Invalid rule %r: target must belong to the %s/%s network" % (argline, vnet_base, vnet_mask)
        continue
    
    if (target_ip_int & mask_int) != vnet_int:
        print >>sys.stderr, "Invalid rule %r: target must belong to the %s/%s network" % (argline, vnet_base, vnet_mask)
        continue
    
    if (gw_ip_int & mask_int) != vnet_int:
        print >>sys.stderr, "Invalid rule %r: gateway must belong to the %s/%s network" % (argline, vnet_base, vnet_mask)
        continue

    # Revalidate command (just in case)
    command = match.group("cmd")
    if command not in ('add','del'):
        print >>sys.stderr, "Invalid rule %r: invalid command" % (argline,)
        continue
    
    # Apply the rule
    routeargs = [ "/sbin/route", command ]
    
    target_ip_str = socket.inet_ntoa(
        struct.pack('!L', target_ip_int))

    gw_ip_str = socket.inet_ntoa(
        struct.pack('!L', gw_ip_int))
    
    if target_mask != 32:
        routeargs.extend([
            "-net", "%s/%d" % (target_ip_str, target_mask)
        ])
    else:
        routeargs.append(target_ip_str)
    
    routeargs.extend([
        "gw", gw_ip_str,
        "dev", ifname,
    ])
    
    proc = subprocess.Popen(routeargs)
    if proc.wait():
        print >>sys.stderr, "Could not set up route"