# Copyright (c) 2015 Openstack Foundation
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import binascii
import collections
import netaddr

from oslo_log import log as logging
from oslo_utils import excutils
import six

from neutron._i18n import _LE, _LW
from neutron.agent.l3 import dvr_fip_ns
from neutron.agent.l3 import dvr_router_base
from neutron.agent.linux import ip_lib
from neutron.common import constants as l3_constants
from neutron.common import exceptions
from neutron.common import utils as common_utils

LOG = logging.getLogger(__name__)
# xor-folding mask used for IPv6 rule index
MASK_30 = 0x3fffffff

# Tracks the arp entry cache
Arp_entry = collections.namedtuple(
    'Arp_entry', 'ip mac subnet_id operation')


class DvrLocalRouter(dvr_router_base.DvrRouterBase):
    def __init__(self, agent, host, *args, **kwargs):
        super(DvrLocalRouter, self).__init__(agent, host, *args, **kwargs)

        self.floating_ips_dict = {}
        # Linklocal subnet for router and floating IP namespace link
        self.rtr_fip_subnet = None
        self.dist_fip_count = None
        self.fip_ns = None
        self._pending_arp_set = set()

    def get_floating_ips(self):
        """Filter Floating IPs to be hosted on this agent."""
        floating_ips = super(DvrLocalRouter, self).get_floating_ips()
        return [i for i in floating_ips if i['host'] == self.host]

    def _handle_fip_nat_rules(self, interface_name):
        """Configures NAT rules for Floating IPs for DVR."""
        self.iptables_manager.ipv4['nat'].empty_chain('POSTROUTING')
        self.iptables_manager.ipv4['nat'].empty_chain('snat')

        # Add back the jump to float-snat
        self.iptables_manager.ipv4['nat'].add_rule('snat', '-j $float-snat')

        # And add the NAT rule back
        rule = ('POSTROUTING', '! -i %(interface_name)s '
                '! -o %(interface_name)s -m conntrack ! '
                '--ctstate DNAT -j ACCEPT' %
                {'interface_name': interface_name})
        self.iptables_manager.ipv4['nat'].add_rule(*rule)

        self.iptables_manager.apply()

    def floating_ip_added_dist(self, fip, fip_cidr):
        """Add floating IP to FIP namespace."""
        floating_ip = fip['floating_ip_address']
        fixed_ip = fip['fixed_ip_address']
        rule_pr = self.fip_ns.allocate_rule_priority(floating_ip)
        self.floating_ips_dict[floating_ip] = rule_pr
        fip_2_rtr_name = self.fip_ns.get_int_device_name(self.router_id)
        ip_rule = ip_lib.IPRule(namespace=self.ns_name)
        ip_rule.rule.add(ip=fixed_ip,
                         table=dvr_fip_ns.FIP_RT_TBL,
                         priority=rule_pr)
        #Add routing rule in fip namespace
        fip_ns_name = self.fip_ns.get_name()
        if self.rtr_fip_subnet is None:
            self.rtr_fip_subnet = self.fip_ns.local_subnets.allocate(
                self.router_id)
        rtr_2_fip, _ = self.rtr_fip_subnet.get_pair()
        device = ip_lib.IPDevice(fip_2_rtr_name, namespace=fip_ns_name)
        device.route.add_route(fip_cidr, str(rtr_2_fip.ip))
        interface_name = (
            self.fip_ns.get_ext_device_name(
                self.fip_ns.agent_gateway_port['id']))
        ip_lib.send_ip_addr_adv_notif(fip_ns_name,
                                      interface_name,
                                      floating_ip,
                                      self.agent_conf)
        # update internal structures
        self.dist_fip_count = self.dist_fip_count + 1

    def floating_ip_removed_dist(self, fip_cidr):
        """Remove floating IP from FIP namespace."""
        floating_ip = fip_cidr.split('/')[0]
        rtr_2_fip_name = self.fip_ns.get_rtr_ext_device_name(self.router_id)
        fip_2_rtr_name = self.fip_ns.get_int_device_name(self.router_id)
        if self.rtr_fip_subnet is None:
            self.rtr_fip_subnet = self.fip_ns.local_subnets.allocate(
                self.router_id)

        rtr_2_fip, fip_2_rtr = self.rtr_fip_subnet.get_pair()
        fip_ns_name = self.fip_ns.get_name()
        if floating_ip in self.floating_ips_dict:
            rule_pr = self.floating_ips_dict[floating_ip]
            ip_rule = ip_lib.IPRule(namespace=self.ns_name)
            ip_rule.rule.delete(ip=floating_ip,
                                table=dvr_fip_ns.FIP_RT_TBL,
                                priority=rule_pr)
            self.fip_ns.deallocate_rule_priority(floating_ip)
            #TODO(rajeev): Handle else case - exception/log?

        device = ip_lib.IPDevice(fip_2_rtr_name, namespace=fip_ns_name)

        device.route.delete_route(fip_cidr, str(rtr_2_fip.ip))
        # check if this is the last FIP for this router
        self.dist_fip_count = self.dist_fip_count - 1
        if self.dist_fip_count == 0:
            #remove default route entry
            device = ip_lib.IPDevice(rtr_2_fip_name, namespace=self.ns_name)
            ns_ip = ip_lib.IPWrapper(namespace=fip_ns_name)
            device.route.delete_gateway(str(fip_2_rtr.ip),
                                        table=dvr_fip_ns.FIP_RT_TBL)
            self.fip_ns.local_subnets.release(self.router_id)
            self.rtr_fip_subnet = None
            ns_ip.del_veth(fip_2_rtr_name)
            self.fip_ns.unsubscribe(self.router_id)
            # NOTE (Swami): The fg interface and the namespace will be deleted
            # when the external gateway port is removed. This will be
            # initiated from the server through an RPC call.

    def add_floating_ip(self, fip, interface_name, device):
        if not self._add_fip_addr_to_device(fip, device):
            return l3_constants.FLOATINGIP_STATUS_ERROR

        # Special Handling for DVR - update FIP namespace
        ip_cidr = common_utils.ip_to_cidr(fip['floating_ip_address'])
        self.floating_ip_added_dist(fip, ip_cidr)
        return l3_constants.FLOATINGIP_STATUS_ACTIVE

    def remove_floating_ip(self, device, ip_cidr):
        super(DvrLocalRouter, self).remove_floating_ip(device, ip_cidr)
        self.floating_ip_removed_dist(ip_cidr)

    def _get_internal_port(self, subnet_id):
        """Return internal router port based on subnet_id."""
        router_ports = self.router.get(l3_constants.INTERFACE_KEY, [])
        for port in router_ports:
            fips = port['fixed_ips']
            for f in fips:
                if f['subnet_id'] == subnet_id:
                    return port

    def _cache_arp_entry(self, ip, mac, subnet_id, operation):
        """Cache the arp entries if device not ready."""
        arp_entry_tuple = Arp_entry(ip=ip,
                                    mac=mac,
                                    subnet_id=subnet_id,
                                    operation=operation)
        self._pending_arp_set.add(arp_entry_tuple)

    def _process_arp_cache_for_internal_port(self, subnet_id):
        """Function to process the cached arp entries."""
        arp_remove = set()
        for arp_entry in self._pending_arp_set:
            if subnet_id == arp_entry.subnet_id:
                try:
                    state = self._update_arp_entry(
                        arp_entry.ip, arp_entry.mac,
                        arp_entry.subnet_id, arp_entry.operation)
                except Exception:
                    state = False
                if state:
                    # If the arp update was successful, then
                    # go ahead and add it to the remove set
                    arp_remove.add(arp_entry)

        self._pending_arp_set -= arp_remove

    def _delete_arp_cache_for_internal_port(self, subnet_id):
        """Function to delete the cached arp entries."""
        arp_delete = set()
        for arp_entry in self._pending_arp_set:
            if subnet_id == arp_entry.subnet_id:
                arp_delete.add(arp_entry)
        self._pending_arp_set -= arp_delete

    def _update_arp_entry(self, ip, mac, subnet_id, operation):
        """Add or delete arp entry into router namespace for the subnet."""
        port = self._get_internal_port(subnet_id)
        # update arp entry only if the subnet is attached to the router
        if not port:
            return False

        try:
            # TODO(mrsmith): optimize the calls below for bulk calls
            interface_name = self.get_internal_device_name(port['id'])
            device = ip_lib.IPDevice(interface_name, namespace=self.ns_name)
            if device.exists():
                if operation == 'add':
                    device.neigh.add(ip, mac)
                elif operation == 'delete':
                    device.neigh.delete(ip, mac)
                return True
            else:
                if operation == 'add':
                    LOG.warn(_LW("Device %s does not exist so ARP entry "
                                 "cannot be updated, will cache information "
                                 "to be applied later when the device exists"),
                             device)
                    self._cache_arp_entry(ip, mac, subnet_id, operation)
                return False
        except Exception:
            with excutils.save_and_reraise_exception():
                LOG.exception(_LE("DVR: Failed updating arp entry"))

    def _set_subnet_arp_info(self, subnet_id):
        """Set ARP info retrieved from Plugin for existing ports."""
        # TODO(Carl) Can we eliminate the need to make this RPC while
        # processing a router.
        subnet_ports = self.agent.get_ports_by_subnet(subnet_id)

        for p in subnet_ports:
            if p['device_owner'] not in l3_constants.ROUTER_INTERFACE_OWNERS:
                for fixed_ip in p['fixed_ips']:
                    self._update_arp_entry(fixed_ip['ip_address'],
                                           p['mac_address'],
                                           subnet_id,
                                           'add')
        self._process_arp_cache_for_internal_port(subnet_id)

    @staticmethod
    def _get_snat_idx(ip_cidr):
        """Generate index for DVR snat rules and route tables.

        The index value has to be 32 bits or less but more than the system
        generated entries i.e. 32768. For IPv4 use the numeric value of the
        cidr. For IPv6 generate a crc32 bit hash and xor-fold to 30 bits.
        Use the freed range to extend smaller values so that they become
        greater than system generated entries.
        """
        net = netaddr.IPNetwork(ip_cidr)
        if net.version == 6:
            if isinstance(ip_cidr, six.text_type):
                ip_cidr = ip_cidr.encode()  # Needed for Python 3.x
            # the crc32 & 0xffffffff is for Python 2.6 and 3.0 compatibility
            snat_idx = binascii.crc32(ip_cidr) & 0xffffffff
            # xor-fold the hash to reserve upper range to extend smaller values
            snat_idx = (snat_idx >> 30) ^ (snat_idx & MASK_30)
            if snat_idx < 32768:
                snat_idx = snat_idx + MASK_30
        else:
            snat_idx = net.value
        return snat_idx

    def _delete_gateway_device_if_exists(self, ns_ip_device, gw_ip_addr,
                                         snat_idx):
        try:
            ns_ip_device.route.delete_gateway(gw_ip_addr,
                                        table=snat_idx)
        except exceptions.DeviceNotFoundError:
            pass

    def _snat_redirect_modify(self, gateway, sn_port, sn_int, is_add):
        """Adds or removes rules and routes for SNAT redirection."""
        try:
            ns_ipr = ip_lib.IPRule(namespace=self.ns_name)
            ns_ipd = ip_lib.IPDevice(sn_int, namespace=self.ns_name)
            if is_add:
                ns_ipwrapr = ip_lib.IPWrapper(namespace=self.ns_name)
            for port_fixed_ip in sn_port['fixed_ips']:
                # Iterate and find the gateway IP address matching
                # the IP version
                port_ip_addr = port_fixed_ip['ip_address']
                port_ip_vers = netaddr.IPAddress(port_ip_addr).version
                for gw_fixed_ip in gateway['fixed_ips']:
                    gw_ip_addr = gw_fixed_ip['ip_address']
                    if netaddr.IPAddress(gw_ip_addr).version == port_ip_vers:
                        sn_port_cidr = common_utils.ip_to_cidr(
                            port_ip_addr, port_fixed_ip['prefixlen'])
                        snat_idx = self._get_snat_idx(sn_port_cidr)
                        if is_add:
                            ns_ipd.route.add_gateway(gw_ip_addr,
                                                     table=snat_idx)
                            ns_ipr.rule.add(ip=sn_port_cidr,
                                            table=snat_idx,
                                            priority=snat_idx)
                            ns_ipwrapr.netns.execute(
                                ['sysctl', '-w',
                                 'net.ipv4.conf.%s.send_redirects=0' % sn_int])
                        else:
                            self._delete_gateway_device_if_exists(ns_ipd,
                                                                  gw_ip_addr,
                                                                  snat_idx)
                            ns_ipr.rule.delete(ip=sn_port_cidr,
                                               table=snat_idx,
                                               priority=snat_idx)
        except Exception:
            if is_add:
                exc = _LE('DVR: error adding redirection logic')
            else:
                exc = _LE('DVR: snat remove failed to clear the rule '
                          'and device')
            LOG.exception(exc)

    def _snat_redirect_add(self, gateway, sn_port, sn_int):
        """Adds rules and routes for SNAT redirection."""
        self._snat_redirect_modify(gateway, sn_port, sn_int, is_add=True)

    def _snat_redirect_remove(self, gateway, sn_port, sn_int):
        """Removes rules and routes for SNAT redirection."""
        self._snat_redirect_modify(gateway, sn_port, sn_int, is_add=False)

    def internal_network_added(self, port):
        super(DvrLocalRouter, self).internal_network_added(port)

        # NOTE: The following function _set_subnet_arp_info
        # should be called to dynamically populate the arp
        # entries for the dvr services ports into the router
        # namespace. This does not have dependency on the
        # external_gateway port or the agent_mode.
        for subnet in port['subnets']:
            self._set_subnet_arp_info(subnet['id'])
        self._snat_redirect_add_from_port(port)

    def _snat_redirect_add_from_port(self, port):
        ex_gw_port = self.get_ex_gw_port()
        if not ex_gw_port:
            return

        sn_port = self.get_snat_port_for_internal_port(port)
        if not sn_port:
            return

        interface_name = self.get_internal_device_name(port['id'])
        self._snat_redirect_add(sn_port, port, interface_name)

    def _dvr_internal_network_removed(self, port):
        if not self.ex_gw_port:
            return

        sn_port = self.get_snat_port_for_internal_port(port, self.snat_ports)
        if not sn_port:
            return

        # DVR handling code for SNAT
        interface_name = self.get_internal_device_name(port['id'])
        self._snat_redirect_remove(sn_port, port, interface_name)
        # Clean up the cached arp entries related to the port subnet
        for subnet in port['subnets']:
            self._delete_arp_cache_for_internal_port(subnet)

    def internal_network_removed(self, port):
        self._dvr_internal_network_removed(port)
        super(DvrLocalRouter, self).internal_network_removed(port)

    def get_floating_agent_gw_interface(self, ext_net_id):
        """Filter Floating Agent GW port for the external network."""
        fip_ports = self.router.get(l3_constants.FLOATINGIP_AGENT_INTF_KEY, [])
        return next(
            (p for p in fip_ports if p['network_id'] == ext_net_id), None)

    def get_external_device_interface_name(self, ex_gw_port):
        fip_int = self.fip_ns.get_int_device_name(self.router_id)
        if ip_lib.device_exists(fip_int, namespace=self.fip_ns.get_name()):
            return self.fip_ns.get_rtr_ext_device_name(self.router_id)

    def external_gateway_added(self, ex_gw_port, interface_name):
        # TODO(Carl) Refactor external_gateway_added/updated/removed to use
        # super class implementation where possible.  Looks like preserve_ips,
        # and ns_name are the key differences.
        ip_wrapr = ip_lib.IPWrapper(namespace=self.ns_name)
        ip_wrapr.netns.execute(['sysctl', '-w',
                               'net.ipv4.conf.all.send_redirects=0'])
        for p in self.internal_ports:
            gateway = self.get_snat_port_for_internal_port(p)
            id_name = self.get_internal_device_name(p['id'])
            if gateway:
                self._snat_redirect_add(gateway, p, id_name)

        for port in self.get_snat_interfaces():
            for ip in port['fixed_ips']:
                self._update_arp_entry(ip['ip_address'],
                                       port['mac_address'],
                                       ip['subnet_id'],
                                       'add')

    def external_gateway_updated(self, ex_gw_port, interface_name):
        pass

    def external_gateway_removed(self, ex_gw_port, interface_name):
        # TODO(Carl) Should this be calling process_snat_dnat_for_fip?
        self.process_floating_ip_nat_rules()
        if self.fip_ns:
            to_fip_interface_name = (
                self.get_external_device_interface_name(ex_gw_port))
            self.process_floating_ip_addresses(to_fip_interface_name)
        for p in self.internal_ports:
            # NOTE: When removing the gateway port, pass in the snat_port
            # cache along with the current ports.
            gateway = self.get_snat_port_for_internal_port(p, self.snat_ports)
            internal_interface = self.get_internal_device_name(p['id'])
            self._snat_redirect_remove(gateway, p, internal_interface)

    def _handle_router_snat_rules(self, ex_gw_port, interface_name):
        pass

    def process_external(self, agent):
        ex_gw_port = self.get_ex_gw_port()
        if ex_gw_port:
            self.create_dvr_fip_interfaces(ex_gw_port)
        super(DvrLocalRouter, self).process_external(agent)

    def create_dvr_fip_interfaces(self, ex_gw_port):
        floating_ips = self.get_floating_ips()
        fip_agent_port = self.get_floating_agent_gw_interface(
            ex_gw_port['network_id'])
        if fip_agent_port:
            LOG.debug("FloatingIP agent gateway port received from the "
                "plugin: %s", fip_agent_port)
        is_first = False
        if floating_ips:
            is_first = self.fip_ns.subscribe(self.router_id)
            if is_first and not fip_agent_port:
                LOG.debug("No FloatingIP agent gateway port possibly due to "
                          "late binding of the private port to the host, "
                          "requesting agent gateway port for 'network-id' :"
                          "%s", ex_gw_port['network_id'])
                fip_agent_port = self.agent.plugin_rpc.get_agent_gateway_port(
                    self.agent.context, ex_gw_port['network_id'])
                if not fip_agent_port:
                    LOG.error(_LE("No FloatingIP agent gateway port "
                                  "returned from server for 'network-id': "
                                  "%s"), ex_gw_port['network_id'])
            if is_first and fip_agent_port:
                if 'subnets' not in fip_agent_port:
                    LOG.error(_LE('Missing subnet/agent_gateway_port'))
                else:
                    self.fip_ns.create_gateway_port(fip_agent_port)

            if (self.fip_ns.agent_gateway_port and
                (self.dist_fip_count == 0 or is_first)):
                self.fip_ns.create_rtr_2_fip_link(self)

                # kicks the FW Agent to add rules for the IR namespace if
                # configured
                self.agent.process_router_add(self)

    def process(self, agent):
        ex_gw_port = self.get_ex_gw_port()
        if ex_gw_port:
            self.fip_ns = agent.get_fip_ns(ex_gw_port['network_id'])
            self.fip_ns.scan_fip_ports(self)

        super(DvrLocalRouter, self).process(agent)
