network_1.py

import queue
import threading
from collections import OrderedDict, defaultdict
import re


## wrapper class for a queue of packets
class Interface:
    ## @param maxsize - the maximum size of the queue storing packets
    def __init__(self, maxsize=0):
        self.in_queue = queue.Queue(maxsize)
        self.out_queue = queue.Queue(maxsize)

    ##get packet from the queue interface
    # @param in_or_out - use 'in' or 'out' interface
    def get(self, in_or_out):
        try:
            if in_or_out == 'in':
                pkt_S = self.in_queue.get(False)
                # if pkt_S is not None:
                #     print('getting packet from the IN queue')
                return pkt_S
            else:
                pkt_S = self.out_queue.get(False)
                # if pkt_S is not None:
                #     print('getting packet from the OUT queue')
                return pkt_S
        except queue.Empty:
            return None

    ##put the packet into the interface queue
    # @param pkt - Packet to be inserted into the queue
    # @param in_or_out - use 'in' or 'out' interface
    # @param block - if True, block until room in queue, if False may throw queue.Full exception
    def put(self, pkt, in_or_out, block=False):
        if in_or_out == 'out':
            # print('putting packet in the OUT queue')
            self.out_queue.put(pkt, block)
        else:
            # print('putting packet in the IN queue')
            self.in_queue.put(pkt, block)


## Implements a network layer packet.
class NetworkPacket:
    ## packet encoding lengths
    dst_S_length = 5
    prot_S_length = 1

    ##@param dst: address of the destination host
    # @param data_S: packet payload
    # @param prot_S: upper layer protocol for the packet (data, or control)
    def __init__(self, dst, prot_S, data_S):
        self.dst = dst
        self.data_S = data_S
        self.prot_S = prot_S

    ## called when printing the object
    def __str__(self):
        return self.to_byte_S()

    ## convert packet to a byte string for transmission over links
    def to_byte_S(self):
        byte_S = str(self.dst).zfill(self.dst_S_length)
        if self.prot_S == 'data':
            byte_S += '1'
        elif self.prot_S == 'control':
            byte_S += '2'
        else:
            raise('%s: unknown prot_S option: %s' %(self, self.prot_S))
        byte_S += self.data_S
        return byte_S

    ## extract a packet object from a byte string
    # @param byte_S: byte string representation of the packet
    @classmethod
    def from_byte_S(self, byte_S):
        dst = byte_S[0 : NetworkPacket.dst_S_length].strip('0')
        prot_S = byte_S[NetworkPacket.dst_S_length : NetworkPacket.dst_S_length + NetworkPacket.prot_S_length]
        if prot_S == '1':
            prot_S = 'data'
        elif prot_S == '2':
            prot_S = 'control'
        else:
            raise('%s: unknown prot_S field: %s' %(self, prot_S))
        data_S = byte_S[NetworkPacket.dst_S_length + NetworkPacket.prot_S_length : ]
        return self(dst, prot_S, data_S)




## Implements a network host for receiving and transmitting data
class Host:

    ##@param addr: address of this node represented as an integer
    def __init__(self, addr):
        self.addr = addr
        self.intf_L = [Interface()]
        self.stop = False #for thread termination

    ## called when printing the object
    def __str__(self):
        return self.addr

    ## create a packet and enqueue for transmission
    # @param dst: destination address for the packet
    # @param data_S: data being transmitted to the network layer
    def udt_send(self, dst, data_S):
        p = NetworkPacket(dst, 'data', data_S)
        print('%s: SENDING PACKET "%s"' % (self, p))
        self.intf_L[0].put(p.to_byte_S(), 'out') #send packets always enqueued successfully

    ## receive packet from the network layer
    def udt_receive(self):
        pkt_S = self.intf_L[0].get('in')
        if pkt_S is not None:
            print('%s: RECIEVED PACKET "%s"' % (self, pkt_S))

    ## thread target for the host to keep receiving data
    def run(self):
        print (threading.currentThread().getName() + ': Starting')
        while True:
            #receive data arriving to the in interface
            self.udt_receive()
            #terminate
            if(self.stop):
                print (threading.currentThread().getName() + ': Ending')
                return



## Implements a multi-interface router
class Router:


    ##@param name: friendly router name for debugging
    # @param cost_D: cost table to neighbors {neighbor: {interface: cost}}
    # @param max_queue_size: max queue length (passed to Interface)
    def __init__(self, name, cost_D, max_queue_size):
        self.stop = False #for thread termination
        self.name = name
        #create a list of interfaces
        self.intf_L = [Interface(max_queue_size) for _ in range(len(cost_D))]
        #save neighbors and interfeces on which we connect to them
        self.neighbors = cost_D    # {neighbor: {interface: cost}}
        self.rt_tbl_D = cost_D.copy()      # {destination: {router: cost}}
        self.total_rt = defaultdict(dict)
        for neighbor_name, neighbor_info in self.neighbors.items():
                for interface,cost in neighbor_info.items():
                    self.total_rt[name][neighbor_name] = [cost]
        print('%s: Initialized routing table' % self)
        self.print_routes()


    ## called when printing the object
    def __str__(self):
        return self.name


    ## look through the content of incoming interfaces and
    # process data and control packets
    def process_queues(self):
        for i in range(len(self.intf_L)):
            pkt_S = None
            #get packet from interface i
            pkt_S = self.intf_L[i].get('in')
            #if packet exists make a forwarding decision
            if pkt_S is not None:
                p = NetworkPacket.from_byte_S(pkt_S) #parse a packet out
                if p.prot_S == 'data':
                    self.forward_packet(p,i)
                elif p.prot_S == 'control':
                    self.update_routes(p, i)
                else:
                    raise Exception('%s: Unknown packet type in packet %s' % (self, p))


    ## forward the packet according to the routing table
    #  @param p Packet to forward
    #  @param i Incoming interface number for packet p
    def forward_packet(self, p, i):
        try:
            route = self.rt_tbl_D.get(str(p.dst)) #look up destination in routing table
            for interface, cost in route.items(): #look up which interface to forward to
                j = int(interface)
                break
            self.intf_L[j].put(p.to_byte_S(), 'out', True)
            print('%s: forwarding packet "%s" from interface %d to %d' % \
                (self, p, i, j))
        except queue.Full:
            print('%s: packet "%s" lost on interface %d' % (self, p, i))
            pass


    ## send out route update
    # @param i Interface number on which to send out a routing update
    def send_routes(self, i): #ENCODING: NAME///NODE/LINK/COST//NODE/LINK/COST//....
        print('sending_routes')
        contents = self.name + "->"  # encode name of router
        for k, j in self.rt_tbl_D.items():
            for link, cost in j.items():
                contents += str(k) + "_" + str(link) + "_" + str(
                    cost) + "#"  # one '/' seperates route from link and cost, two '/' seperates route from other route
        p = NetworkPacket(0, 'control', contents)
        self.intf_L[i].put(p.to_byte_S(), 'out', True)



    ## forward the packet according to the routing table
    #  @param p Packet containing routing information
    def update_routes(self, p, i):
        updateFlag = 0
        contents = p.data_S.split("->") #decode packet
        name = contents[0]
        routeList = contents[1].split("#")
        for i in routeList: #for all routes in this routing table
            if i != '':
                nodeList = i.split("_")

            curNode = nodeList[0]
            nodePar = int(nodeList[2])
            self.total_rt[name][curNode] = [nodePar]

            if curNode == self.name:
                neiKeyValue =  int(list(self.neighbors[name].keys())[0])
                self.rt_tbl_D[curNode] = {neiKeyValue:0}
                self.total_rt[self.name][curNode] = [0]
                continue
            else:
                if curNode not in self.neighbors and  curNode not in self.rt_tbl_D:
                    neiNameValue  = list(self.neighbors[name].values())[0]
                    neiKeyValue = int(list(self.neighbors[name].keys())[0])
                    self.rt_tbl_D[curNode] = {neiKeyValue:nodePar + neiNameValue}
                    self.total_rt[self.name][curNode] = [nodePar + neiNameValue]
                    updateFlag = 1
                elif curNode not in self.neighbors and  curNode in self.rt_tbl_D:
                    neiNameValue  = list(self.neighbors[name].values())[0]
                    neiKeyValue=  int(list(self.neighbors[name].keys())[0])
                    curNodeValue = list(self.rt_tbl_D[curNode].values())[0]
                    if curNodeValue > int(neiNameValue) + nodePar:
                        self.rt_tbl_D[curNode] = {neiKeyValue:nodePar + neiNameValue}
                        self.total_rt[self.name][curNode] = [nodePar + neiNameValue]
                        updateFlag = 1
        if updateFlag == 1:
            for neighbor_name, neighbor_info in self.neighbors.items():
                for interface,cost in neighbor_info.items():
                    if 'R' in neighbor_name:
                        self.send_routes(interface)

    ## Print routing table
    def print_routes(self):

        costTable = []
        print('cost table for %s: ' % self)
        sort_tbl = OrderedDict(sorted(self.total_rt.items()))
        interfaces = []
        for i,j in sort_tbl.items():
            for link,cost in j.items():
                if not link in interfaces:
                    interfaces.append(link)
        interfaces = sorted(interfaces)

        for interface in interfaces:
            print(str(interface) + "\t", end='')
            for i, j in sort_tbl.items():
                for link,cost in j.items():
                    if link == interface:
                        print(str(cost) + "\t", end='')
                        costTable +=[cost]

        print("\n")
        tablestr1 = ''
        tablestr2 = ''
        for i in range(int(len(costTable)/2+1)):
            tablestr1+='| '
            tablestr1+= str(costTable[(i-1)*2])
            if i< len(costTable):
                tablestr2 += '| '
                tablestr2 += str(costTable[(i-1)*2+1])
        tablestr1 += ' | '
        tablestr2 += ' | '
        print(tablestr1)
        print(tablestr2)

        print("\n")



    ## thread target for the host to keep forwarding data
    def run(self):
        print (threading.currentThread().getName() + ': Starting')
        while True:
            self.process_queues()
            if self.stop:
                print (threading.currentThread().getName() + ': Ending')
                return