Add multicast routing

See merge request nexedi/re6stnet!37

README.rst

@@ -59,6 +59,7 @@ Requirements
 - geoip2: `python library`_ and `country lite database`_ (optional)
 - python-miniupnpc for UPnP support (optional)
 - for the demo: miniupnpd_, Graphviz, Screen_, Nemu_, MultiPing_, psutil_
+- for multicast: pim-dm_ and PyYAML_
 
 See also `setup.py` for Python dependencies.
 
@@ -70,6 +71,8 @@ See also `setup.py` for Python dependencies.
 .. _Screen: http://savannah.gnu.org/projects/screen
 .. _python library: https://pypi.org/project/geoip2/
 .. _country lite database: https://dev.maxmind.com/geoip/geoip2/geolite2/
+.. _pim-dm: https://pypi.org/project/pim-dm/
+.. _PyYAML: https://pypi.org/project/PyYAML/
 
 Installation
 ============

re6st/cli/node.py

@@ -50,6 +50,8 @@ def getConfig():
     _('-I', '--main-interface', metavar='IFACE', default='lo',
         help="Set re6stnet IP on given interface. Any interface not used for"
              " tunnelling can be chosen.")
+    _('-m', '--multicast', action='store_true',
+        help="Enable multicast routing.")
     _('--up', metavar='CMD',
         help="Shell command to run after successful initialization.")
     _('--daemon', action='append', metavar='CMD',
@@ -364,6 +366,12 @@ def main():
                     R[r] = partial(tunnel_manager.handleServerEvent, r)
                     x.close()
 
+            if config.multicast:
+                from re6st.multicast import PimDm
+                pimdm = PimDm()
+                cleanup.append(pimdm.run(config.iface_list, config.run).stop)
+                R[pimdm.s_netlink] = pimdm.addInterfaceWhenReady
+
             ip('addr', my_ip + '/%s' % len(subnet),
                'dev', config.main_interface)
             if_rt = ['ip', '-6', 'route', 'del',

re6st/multicast.py

+import os, struct, subprocess, time, yaml
+from ctypes import (
+    Structure, Union, POINTER,
+    pointer, c_ushort, c_byte, c_void_p, c_char_p, c_uint, c_int,
+    CDLL, util as ctypes_util,
+)
+from socket import socket, AF_INET6, AF_NETLINK, NETLINK_ROUTE, SOCK_RAW
+from . import utils
+
+RTMGRP_IPV6_IFINFO = 0x800
+RTM_NEWLINK = 16
+IFLA_IFNAME = 3
+
+class struct_sockaddr(Structure):
+    _fields_ = [
+        ('sa_family', c_ushort),
+        ('sa_data', c_byte * 14),
+    ]
+
+class union_ifa_ifu(Union):
+    _fields_ = [
+        ('ifu_broadaddr', POINTER(struct_sockaddr)),
+        ('ifu_dstaddr', POINTER(struct_sockaddr)),
+    ]
+
+class struct_ifaddrs(Structure):
+    pass
+struct_ifaddrs._fields_ = [
+    ('ifa_next', POINTER(struct_ifaddrs)),
+    ('ifa_name', c_char_p),
+    ('ifa_flags', c_uint),
+    ('ifa_addr', POINTER(struct_sockaddr)),
+    ('ifa_netmask', POINTER(struct_sockaddr)),
+    ('ifa_ifu', union_ifa_ifu),
+    ('ifa_data', c_void_p),
+]
+
+libc = CDLL(ctypes_util.find_library('c'), use_errno=True)
+getifaddrs = libc.getifaddrs
+getifaddrs.restype = c_int
+getifaddrs.argtypes = [POINTER(POINTER(struct_ifaddrs))]
+freeifaddrs = libc.freeifaddrs
+freeifaddrs.restype = None
+freeifaddrs.argtypes = [POINTER(struct_ifaddrs)]
+
+class unpacker(object):
+
+    def __init__(self, buf):
+        self._buf = buf
+        self._offset = 0
+
+    def __call__(self, fmt):
+        s = struct.Struct(fmt)
+        result = s.unpack_from(self._buf, self._offset)
+        self._offset += s.size
+        return result
+
+class PimDm(object):
+
+    def __init__(self):
+        s_netlink = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)
+        s_netlink.setblocking(False)
+        s_netlink.bind((os.getpid(), RTMGRP_IPV6_IFINFO))
+        self.s_netlink = s_netlink
+
+        self.started = False
+
+    def addInterface(self, ifname):
+        while not self.isStarted():
+            time.sleep(0.5)
+        subprocess.call(['pim-dm', '-6', '-aisr', ifname])
+        subprocess.call(['pim-dm', '-aimld', ifname])
+
+    def addInterfaceWhenReady(self):
+        if not self.not_ready_iface_set:
+            return
+
+        data = self.s_netlink.recv(65535)
+        unpack = unpacker(data)
+        msg_len, msg_type, flags, seq, pid = unpack("=LHHLL")
+        if msg_type != RTM_NEWLINK:
+            return
+
+        family, _, if_type, index, flags, change = unpack("=BBHiII")
+
+        while msg_len - unpack._offset:
+            rta_len, rta_type = unpack("=HH")
+            if rta_len < 4:
+                break
+            rta_data = unpack("%ds" % rta_len)[0].rstrip('\0\n\1')
+
+            if rta_type == IFLA_IFNAME:
+                if rta_data in self.not_ready_iface_set \
+                   and rta_data in interfaceUpSet():
+                    self.addInterface(rta_data)
+                    self.not_ready_iface_set.remove(rta_data)
+                break
+
+            unpack._offset += (rta_len - 1) & ~(4 - 1)
+
+    def isStarted(self):
+        if not self.started:
+            self.started = os.path.exists('/run/pim-dm/0')
+        return self.started   
+
+    def run(self, iface_list, run_path):
+        # pim-dm requires interface to be up at startup, 
+        # but can handle interfaces going down then up again
+        iface_set = set(iface_list)
+        up_set = interfaceUpSet()
+        self.not_ready_iface_set = iface_set - up_set
+        iface_set &= up_set
+
+        enabled = (('enabled', True), ('state_refresh', True))
+        conf = {
+            'PIM-DM': {
+                'Interfaces': dict.fromkeys(iface_set, {'ipv6': dict(enabled)}),
+            },
+            'MLD': {
+                'Interfaces': dict.fromkeys(iface_set, dict(enabled[:1])),
+            },
+        }
+
+        conf_file_path = os.path.join(run_path, 'pim-dm.conf')
+        with open(conf_file_path, 'w') as conf_file:
+            yaml.dump(conf, conf_file)
+
+        return utils.Popen(['pim-dm', '-config', conf_file_path])
+
+def ifap_iter(ifa):
+    '''Iterate over linked list of ifaddrs'''
+    while ifa:
+        ifa = ifa.contents
+        yield ifa
+        ifa = ifa.ifa_next
+
+def interfaceUpSet():
+    ifap = POINTER(struct_ifaddrs)()
+    getifaddrs(pointer(ifap))
+    try:
+        return {
+            ifa.ifa_name
+            for ifa in ifap_iter(ifap)
+            if ifa.ifa_addr and ifa.ifa_addr.contents.sa_family == AF_INET6
+        }
+    finally:
+        freeifaddrs(ifap)

setup.py

@@ -94,6 +94,7 @@ setup(
     install_requires = ['pyOpenSSL >= 0.13', 'miniupnpc'],
     extras_require = {
         'geoip': ['geoip2'],
+        'multicast': ['PyYAML'],
     },
     #dependency_links = [
     #    "http://miniupnp.free.fr/files/download.php?file=miniupnpc-1.7.20120714.tar.gz#egg=miniupnpc-1.7",