+#!/usr/bin/env python
+# Copyright (c) 2016 Cisco and/or its affiliates.
+# 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.
+
+"""Traffic script that sends a DHCP ACK message when DHCP REQUEST message is
+received."""
+
+import sys
+
+from scapy.layers.l2 import Ether
+from scapy.layers.inet import IP, UDP
+from scapy.layers.dhcp import BOOTP, DHCP
+
+from resources.libraries.python.PacketVerifier import RxQueue, TxQueue
+from resources.libraries.python.TrafficScriptArg import TrafficScriptArg
+
+
+def is_discover(pkt):
+ """If DHCP message type option is set to dhcp discover return True,
+ else return False. False is returned also if exception occurs."""
+ dhcp_discover = 1
+ try:
+ dhcp_options = pkt['BOOTP']['DHCP options'].options
+ message_type = filter(lambda x: x[0] == 'message-type',
+ dhcp_options)
+ message_type = message_type[0][1]
+ return message_type == dhcp_discover
+ except:
+ return False
+
+
+def is_request(pkt):
+ """If DHCP message type option is DHCP REQUEST return True,
+ else return False. False is returned also if exception occurs."""
+ dhcp_request = 3
+ try:
+ dhcp_options = pkt['BOOTP']['DHCP options'].options
+ message_type = filter(lambda x: x[0] == 'message-type',
+ dhcp_options)
+ message_type = message_type[0][1]
+ return message_type == dhcp_request
+ except:
+ return False
+
+
+def main():
+ """Main function of the script file."""
+ args = TrafficScriptArg(['server_mac', 'server_ip', 'client_ip',
+ 'client_mask', 'lease_time'])
+
+ server_if = args.get_arg('rx_if')
+ server_mac = args.get_arg('server_mac')
+ server_ip = args.get_arg('server_ip')
+
+ client_ip = args.get_arg('client_ip')
+ client_mask = args.get_arg('client_mask')
+
+ lease_time = int(args.get_arg('lease_time'))
+
+ rxq = RxQueue(server_if)
+ txq = TxQueue(server_if)
+ sent_packets = []
+
+ for _ in range(10):
+ dhcp_discover = rxq.recv(10)
+ if is_discover(dhcp_discover):
+ break
+ else:
+ raise RuntimeError("DHCP DISCOVER Rx error.")
+
+ dhcp_offer = Ether(src=server_mac, dst=dhcp_discover.src)
+ dhcp_offer /= IP(src=server_ip, dst="255.255.255.255")
+ dhcp_offer /= UDP(sport=67, dport=68)
+ dhcp_offer /= BOOTP(op=2,
+ xid=dhcp_discover['BOOTP'].xid,
+ yiaddr=client_ip,
+ siaddr=server_ip,
+ chaddr=dhcp_discover['BOOTP'].chaddr)
+ dhcp_offer_options = [("message-type", "offer"), # Option 53
+ ("subnet_mask", client_mask), # Option 1
+ ("server_id", server_ip), # Option 54, dhcp server
+ ("lease_time", lease_time), # Option 51
+ "end"]
+ dhcp_offer /= DHCP(options=dhcp_offer_options)
+
+ txq.send(dhcp_offer)
+ sent_packets.append(dhcp_offer)
+
+ max_other_pkts = 10
+ for _ in range(0, max_other_pkts):
+ dhcp_request = rxq.recv(5, sent_packets)
+ if not dhcp_request:
+ raise RuntimeError("DHCP REQUEST Rx timeout.")
+ if is_request(dhcp_request):
+ break
+ else:
+ raise RuntimeError("Max RX packet limit reached.")
+
+ # Send dhcp ack
+ dhcp_ack = Ether(src=server_mac, dst=dhcp_request.src)
+ dhcp_ack /= IP(src=server_ip, dst="255.255.255.255")
+ dhcp_ack /= UDP(sport=67, dport=68)
+ dhcp_ack /= BOOTP(op=2,
+ xid=dhcp_request['BOOTP'].xid,
+ yiaddr=client_ip,
+ siaddr=server_ip,
+ flags=dhcp_request['BOOTP'].flags,
+ chaddr=dhcp_request['BOOTP'].chaddr)
+ dhcp_ack_options = [("message-type", "ack"), # Option 53. 5: ACK, 6: NAK
+ ("subnet_mask", client_mask), # Option 1
+ ("server_id", server_ip), # Option 54, dhcp server
+ ("lease_time", lease_time), # Option 51,
+ "end"]
+ dhcp_ack /= DHCP(options=dhcp_ack_options)
+
+ txq.send(dhcp_ack)
+ sent_packets.append(dhcp_ack)
+
+ sys.exit(0)
+
+if __name__ == "__main__":
+ main()
Code Review / csit.git / commitdiff