def l3_recvfrom(node, message):
# decode payload
data = json.loads(message)
# get destination nid from payload
dest_nid = data['destination_nid']
# get last nid from payload
last_nid = data['last_nid']
# reset last nid
data['last_nid'] = node.GetNID()
# set variable for segment
segment = data['payload']
# if it is for this node, pass it up to layer 4
if str(dest_nid) == str(node.GetNID()):
Transport.l4_recvfrom(segment)
# if its not for this node, send it back down to layer 2
else:
ttl = data['ttl']
new_ttl = (ttl - 1)
data['ttl'] = new_ttl
if (data['ttl'] > 0):
datagram = json.dumps(data)
Link.l2_sendto(node, last_nid, dest_nid, datagram)
else:
pass
# April 28, 2016
def l3_sendto(node, dest_nid, segment):
# get list of all links from link table and find link for this node
links = node.GetLinks()
link1 = links[0]
# set hostname, port this node
hostname = link1[1]
port = link1[2]
# set sequence number (fix later)
sequence_number = 1
# set sequence total (fix later)
sequence_total = 1
# set ttl (fix later)
ttl = 10
# set length of data segment
data_length = len(segment)
# get port table for this node and set values for destination target
PortTable = node.GetPortTable()
for link in PortTable:
info = PortTable[link]
if info[0] == dest_nid:
dest_hostname = info[1]
dest_port = info[2]
# set last nid value (for routing)
last_nid = node.GetNID()
# build datagram
datagram = {}
datagram['source_hostname'] = node.GetHostName()
datagram['source_nid'] = node.GetNID()
datagram['source_port'] = node.GetPort()
datagram['destination_hostname'] = dest_hostname
datagram['destination_nid'] = dest_nid
datagram['destination_port'] = dest_port
datagram['sequence_number'] = 1
datagram['total_sequence_numbers'] = 1
datagram['ttl'] = 15
datagram['mtu'] = 1000
datagram['length'] = data_length
datagram['payload'] = segment
datagram['last_nid'] = node.GetNID()
# encode payload
payload = json.dumps(datagram)
# pass to link layer for sending
Link.l2_sendto(node, last_nid, payload)
