def callback(frame):
'''
The action after receiving datagram from link layer.
First unpack datagram
Case1: if the outside datagram is received by destination end router,
it will first do NAT and update datgram, then push upward
Case2; if the internal datagram is received by destination,
no need for NAT, directly push upward
Case3: if this datagram is received in core routers,
find the next forwarding hop ip and convert into mac,
then send it by linklayer
:param frame: received datagram from linklayer
:return: None
'''
network, transport, action = unpack(frame)
if action == ACTION_PUSH:
if network.dst_ip == util.get_local_ipv4_address():
IP.push(frame)
elif network.dst_ip in forwarding_table:
forwarding_ip = forwarding_table[network.dst_ip]
if forwarding_ip != WAN_ip:
dst_ip = forwarding_ip
else:
dst_ip = network.dst_ip
if dst_ip != forwarding_ip:
print('forwaring to', forwarding_table[network.dst_ip])
dst_mac = util.ip2mac(dst_ip)
linklayer.sendto(dst_mac, frame)
elif (network.dst_ip, transport.dst_port) in NAT_in :
network.dst_ip, transport.dst_port = NAT_in[(network.dst_ip, transport.dst_port)]
frame = pack(network, transport)
IP.push(frame)
else:
ICMP.host_unreachable(WAN_ip, network.src_ip)
def dijsktra():
'''
This function is to to generate a min cost path for a given start node and update the forwarding table
:param startNode means the given start node
:return: None
'''
global forwarding_table
start_ip = util.get_local_ipv4_address()
# Initialize visited list
notVisited = set()
for i in NETWORK:
notVisited.add(i)
# Initalize min_cost list
min_cost = {}
pre_node = None
# the value of min_cost is a editable list, the first element is min_cost, the second is previous node
for i in NETWORK:
if not i == start_ip:
min_cost[i] = [float('inf'),pre_node]
else:
min_cost[i] = [0,pre_node]
# do dijsktra
while notVisited:
current_node = get_current_node(min_cost, notVisited)
notVisited.remove(current_node)
neighbor_set = NETWORK[current_node]
for key in neighbor_set:
if key[0] in notVisited:
if min_cost[current_node][0] + key[1] < min_cost[key[0]][0]:
min_cost[key[0]][0] = min_cost[current_node][0] +key[1]
min_cost[key[0]][1] = current_node
for key in min_cost:
value = min_cost[key]
path = []
if value[0] == 0:
path.append(key)
# find path by back propagation
while value[1] != None:
path.append(value[1])
value = min_cost[value[1]]
path.reverse()
path.append(key)
if len(path)>1:
forwarding_table[key] = path[1]
elif len(path)==1:
forwarding_table[key] = path[0]
else:
forwarding_table[key] = key
print('pass')
from mysocket import *
from LinkLayer import util
ip = util.get_local_ipv4_address()
port = 5000
local_address = (ip, port)
remote_address = ('10.21.108.47', 5000)
ClientSocket = socket(AF_INET, SOCK_STREAM)
ClientSocket.bind(local_address)
ClientSocket.connect(remote_address)
for i in range(10):
ClientSocket.send("{}".format(i).encode())
raw_message = ClientSocket.recv(2048)
print("\n---------------\n", raw_message.decode(), "\n----------------\n")
def get_local_ip():
return util.get_local_ipv4_address()
