Merge pull request #5 from ryanpetrello/master

Remove arping and send gratuitous ARP via Python's socket lib

akanda/router/drivers/arp.py

@@ -17,8 +17,11 @@
 
 import logging
 import re
+import socket
+import struct
 
 from akanda.router.drivers import base
+from akanda.router.models import Network
 
 
 LOG = logging.getLogger(__name__)
@@ -31,6 +34,71 @@ class ARPManager(base.Manager):
     """
     EXECUTABLE = '/usr/sbin/arp'
 
+    def send_gratuitous_arp_for_floating_ips(self, config, generic_to_host):
+        """
+        Send a gratuitous ARP for every Floating IP.
+        :type config: akanda.router.models.Configuration
+        :param config: An akanda.router.models.Configuration object containing
+                       configuration information for the system's network
+                       setup.
+        :type generic_to_host: callable
+        :param generic_to_host: A callable which translates a generic interface
+                                name (e.g., "ge0") to a physical name (e.g.,
+                                "eth0")
+        """
+        external_nets = filter(
+            lambda n: n.network_type == Network.TYPE_EXTERNAL,
+            config.networks
+        )
+        for net in external_nets:
+            for fip in net.floating_ips:
+                self.send_gratuitous_arp(
+                    generic_to_host(net.interface.ifname),
+                    str(fip.floating_ip)
+                )
+
+    def send_gratuitous_arp(self, ifname, address):
+        """
+        Send a gratuitous ARP reply.  Generally used when Floating IPs are
+        associated.
+        :type ifname: str
+        :param ifname: The real name of the interface to send an ARP on
+        :type address: str
+        :param address: The source IPv4 address
+        """
+        HTYPE_ARP = 0x0806
+        PTYPE_IPV4 = 0x0800
+
+        # Bind to the socket
+        sock = socket.socket(socket.AF_PACKET, socket.SOCK_RAW)
+        sock.bind((ifname, HTYPE_ARP))
+        hwaddr = sock.getsockname()[4]
+
+        # Build a gratuitous ARP packet
+        gratuitous_arp = [
+            struct.pack("!h", 1),  # HTYPE Ethernet
+            struct.pack("!h", PTYPE_IPV4),  # PTYPE IPv4
+            struct.pack("!B", 6),  # HADDR length, 6 for IEEE 802 MAC addresses
+            struct.pack("!B", 4),  # PADDR length, 4 for IPv4
+            struct.pack("!h", 2),  # OPER, 2 = ARP Reply
+
+            # Sender's hardware and protocol address are duplicated in the
+            # target fields
+
+            hwaddr,  # Sender MAC
+            socket.inet_aton(address),  # Sender IP address
+            hwaddr,  # Target MAC
+            socket.inet_aton(address)  # Target IP address
+        ]
+        frame = [
+            '\xff\xff\xff\xff\xff\xff',  # Broadcast destination
+            hwaddr,  # Source address
+            struct.pack("!h", HTYPE_ARP),
+            ''.join(gratuitous_arp)
+        ]
+        sock.send(''.join(frame))
+        sock.close()
+
     def remove_stale_entries(self, config):
         """
         A wrapper function that iterates over the networks in <config> and

akanda/router/drivers/ip.py

@@ -228,14 +228,6 @@ def _update_set(self, real_ifname, interface, old_interface, attribute,
             self.sudo(*fmt_args_add(item))
             self.up(interface)
 
-            # Send a gratuitous ARP for new v4 addressees
-            ip, prefix = item
-            if ip.version == 4:
-                utils.execute([
-                    'arping', '-A', '-c', '1', '-vv', '-I',
-                    real_ifname, str(ip)
-                ], self.root_helper)
-
         for item in (prev_set - next_set):
             self.sudo(*fmt_args_delete(item))
             ip, prefix = item

akanda/router/manager.py

@@ -101,6 +101,10 @@ def update_routes(self, cache):
 
     def update_arp(self):
         mgr = arp.ARPManager()
+        mgr.send_gratuitous_arp_for_floating_ips(
+            self.config,
+            self.ip_mgr.generic_to_host
+        )
         mgr.remove_stale_entries(self.config)
 
     def get_interfaces(self):

scripts/create-akanda-raw-image.sh

@@ -4,7 +4,7 @@ export DEBIAN_FRONTEND=noninteractive
 APT_GET="apt-get -y"
 APPLIANCE_BASE_DIR="/tmp/akanda-appliance"
 APPLIANCE_SCRIPT_DIR="$APPLIANCE_BASE_DIR/scripts"
-PACKAGES="ntp python2.7 python-pip wget dnsmasq bird6 iptables iptables-persistent tcpdump conntrack tshark mtr arping"
+PACKAGES="ntp python2.7 python-pip wget dnsmasq bird6 iptables iptables-persistent tcpdump conntrack tshark mtr"
 PACKAGES_BUILD="python-dev build-essential isc-dhcp-client"
 
 DNS=8.8.8.8

test/unit/drivers/test_arp.py

@@ -16,8 +16,10 @@
 
 
 import mock
+import socket
 import unittest2
 
+from akanda.router import models
 from akanda.router.drivers import arp
 
 config = mock.Mock()
@@ -26,6 +28,13 @@
 network.address_allocations = [alloc]
 config.networks = [network]
 
+def _AF_PACKET_supported():
+    try:
+        from socket import AF_PACKET
+        return True
+    except:
+        return False
+
 
 class ARPTest(unittest2.TestCase):
 
@@ -83,3 +92,81 @@ def test_ip_mac_address_mismatch(self):
                 mock.call('-an'),
                 mock.call('-d', '10.10.10.2')
             ])
+
+    def test_send_gratuitous_arp_for_config(self):
+        config = models.Configuration({
+            'networks': [{
+                'network_id': 'ABC456',
+                'interface': {
+                    'ifname': 'ge1',
+                    'name': 'ext',
+                },
+                'subnets': [{
+                    'cidr': '172.16.77.0/24',
+                    'gateway_ip': '172.16.77.1',
+                    'dhcp_enabled': True,
+                    'dns_nameservers': []
+                }],
+                'network_type': models.Network.TYPE_EXTERNAL,
+            }],
+            'floating_ips': [{
+                'fixed_ip': '192.168.0.2',
+                'floating_ip': '172.16.77.50'
+            },{
+                'fixed_ip': '192.168.0.3',
+                'floating_ip': '172.16.77.51'
+            },{
+                'fixed_ip': '192.168.0.4',
+                'floating_ip': '172.16.77.52'
+            },{
+                'fixed_ip': '192.168.0.5',
+                'floating_ip': '172.16.77.53'
+            }]
+        })
+
+        with mock.patch.object(self.mgr, 'send_gratuitous_arp') as send_garp:
+            self.mgr.send_gratuitous_arp_for_floating_ips(
+                config,
+                lambda x: x.replace('ge', 'eth')
+            )
+            assert send_garp.call_args_list == [
+                mock.call('eth1', '172.16.77.50'),
+                mock.call('eth1', '172.16.77.51'),
+                mock.call('eth1', '172.16.77.52'),
+                mock.call('eth1', '172.16.77.53')
+            ]
+
+    @unittest2.skipIf(
+        not _AF_PACKET_supported(),
+        'socket.AF_PACKET not supported on this platform'
+    )
+    @mock.patch('socket.socket')
+    def test_send_gratuitous_arp(self, socket_constr):
+        socket_inst = socket_constr.return_value
+        socket_inst.getsockname.return_value = (
+            None, None, None, None, 'A1:B2:C3:D4:E5:F6'
+        )
+
+        self.mgr.send_gratuitous_arp('eth1', '1.2.3.4')
+        socket_constr.assert_called_once_with(
+            socket.AF_PACKET, socket.SOCK_RAW
+        )
+        socket_inst.bind.assert_called_once_with((
+            'eth1',
+            0x0806
+        ))
+        data = socket_inst.send.call_args_list[0][0][0]
+        assert data == ''.join([
+            '\xff\xff\xff\xff\xff\xff',  # Broadcast destination
+            'A1:B2:C3:D4:E5:F6',  # Source hardware address
+            '\x08\x06',  # HTYPE ARP
+            '\x00\x01',  # Ethernet
+            '\x08\x00',  # Protocol IPv4
+            '\x06',  # HADDR length, 6 for IEEE 802 MAC addresses
+            '\x04',  # PADDR length, 4 for IPv4
+            '\x00\x02',  # OPER, 2 = ARP Reply
+            'A1:B2:C3:D4:E5:F6',  # Source MAC
+            '\x01\x02\x03\x04',  # Source IP
+            'A1:B2:C3:D4:E5:F6',  # Target MAC matches
+            '\x01\x02\x03\x04'  # Target IP matches
+        ])

test/unit/drivers/test_ip.py

@@ -16,6 +16,7 @@
 
 import logging
 import re
+import socket
 from cStringIO import StringIO
 
 from unittest2 import TestCase
@@ -259,10 +260,6 @@ def test_address_add(self):
                 ], 'sudo'),
                 mock.call([cmd, 'link', 'set', 'em0', 'up'], 'sudo'),
                 mock.call([cmd, 'addr', 'show', 'em0']),
-                mock.call([
-                    'arping', '-A', '-c', '1', '-vv', '-I', 'em0',
-                    '192.168.105.2'
-                ], 'sudo'),
                 mock.call([
                     cmd, '-6', 'addr', 'add',
                     'fdca:3ba5:a17a:acda:20c:29ff:fe94:723d/64', 'dev', 'em0'
@@ -318,9 +315,6 @@ def test_update_set(self):
                 ], 'sudo'),
                 mock.call(['/sbin/ip', 'link', 'set', 'em0', 'up'], 'sudo'),
                 mock.call(['/sbin/ip', 'addr', 'show', 'em0']),
-                mock.call([
-                    'arping', '-A', '-c', '1', '-vv', '-I', 'em0', str(a.ip)
-                ], 'sudo'),
                 mock.call([
                     '/sbin/ip', 'addr', 'del', str(c), 'dev', 'em0'
                 ], 'sudo'),
@@ -378,7 +372,6 @@ def test_get_management_address_with_autoconfiguration(self):
                 mock.call([cmd, 'link', 'set', 'eth0', 'up'], 'sudo')
             ]
 
-
 class TestDisableDAD(TestCase):
     """
     Duplicate Address Detection should be auto-disabled for non-external