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#/usr/bin/env python
# Simple map resolver
#
# This script creates an UDP socket and starts listening on it.
# When a map-request is received nonce is extracted from the request and
# used in map-reply.
#
# Notes:
# * works only with ipv4 in both under/over-lays.
# * exact address matching is done while looking for a mapping
#
# Usage:
# ./dummy_mr <bind-ip> <port>
#
import sys
import socket
# mapping between EIDs and RLOCs
mappings = {
b'\x06\x00\x02\x02' : (b'\x06\x00\x03\x02', ),
b'\x06\x00\x01\x02' : (b'\x06\x00\x03\x01', )
}
# LISP map-reply message
reply_data = (b'\x20\x00\x00\x01' # type, PES, reserved, record count
+ '\x00\x00\x00\x00' # nonce
+ '\x00\x00\x00\x00' # nonce
+ '\x00\x00\x05\xa0' # record TTL
+ '\x01\x18\x10\x00' # loc-count, EID-len, ACT
+ '\x00\x00\x00\x01' # rsvd, map-version, EID-AFI=ipv4
+ '\x06\x00\x02\x00' # EID prefix
+ '\x01\x01\xff\x00' # prio, weight, mprio, mweight
+ '\x00\x05\x00\x01' # unused, LpR, Loc-AFI
+ '\x06\x00\x03\x02') # locator
request_nonce_offset = 36
reply_nonce_offset = 4
request_eid_offset = 60
reply_eid_offset = 24
reply_rloc_offset = 36
def build_reply(nonce, deid):
if deid not in mappings:
raise Exception('No mapping found for eid {}!'.format(repr(deid)))
m = mappings[deid]
# prepare reply data
reply = bytearray(reply_data)
# update rloc field in reply message
rloc = bytearray(m[0])
for i in range(0, 4):
reply[reply_rloc_offset + i] = rloc[i]
# update eid prefix field
for i in range(0, 4):
reply[reply_eid_offset + i] = deid[i]
# update nonce
for i in range(0, 8):
reply[reply_nonce_offset + i] = nonce[i]
return reply
def run(host, port):
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_address = (host, int(port))
sock.bind(server_address)
while True:
data, address = sock.recvfrom(4096)
# extract nonce from request
nonce = data[request_nonce_offset:request_nonce_offset+8]
# extract deid
deid = data[request_eid_offset:request_eid_offset+4]
rp = build_reply(nonce, deid)
sock.sendto(rp, address)
if __name__ == "__main__":
if len(sys.argv) < 2:
raise Exception('IP and port expected')
run(sys.argv[1], sys.argv[2])
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