Group Members
==============
Member 1
--------
Name 	: Keshav Velhal
SBU ID	: 110276432
Email	: [email protected]

Member 2
--------
Name	: Neeraj Dixit
SBU ID	: 109951838
Email	: [email protected]

USER Documentation:
===================
- The complete assignment consists of 3 .C file namely server.c, client.c,odr.c
  and the Makefile and README
- To compile the assignment just run the command 'make' in the assignment
  directory
- To clean the executable files just run the command 'make clean' in the
  assignment directory
- First deploy the the three execulable files client, odr and server on t
  the virtual machines's-1 to 10.
   Example:
  ~/cse533/deploy_app client server odr 
- To invoke the client just execute 'client' executable on any virtual machine.
  Example:   
  ./client
- To choose    vm's from 1 to 10 enter any number from 1-10.
  
- To invoke the server just execute 'server' executable on any virtual machine.
  Example:   
  ./server
  or
  ~/cse533/start_app server
- The odr should be started on all the virtual machines. The staleness paramater 
  must be passed as arguments.
  Example:
   ~/cse533/start_app "odr 10" 
    or  
  ./odr 10 
 
 System Documentation:  
 ==================== 
  1. CLIENT:
     - Client prompts the user to choose vm's from 1 to 10,so as to communicate with that server.
	 - Then client binds to the temporary path name on the unix socket.
	 - Client sends  the  information to the  be sent to the server prompted by user this is done 
	   in msg_send function.
	 - In the msg_send function 
	   Client sends the information to be sent to the server through the odr.Message is sent on the 
	   odr_path.
     - The message sent is a single character sequence which contains the 
	   following information :
       socket descipter of write,canonical ip address of destination,port number of destination and 
	   message to be sent,route_rediscovery flag.
     - Then the client waits till a time_out (using select) occurs to receive message from the server.
     - The msg_recv fuction 
	   client receive's the information sent by the server through the odr(on odr_path). 
	   The message_received is in   a single character sequence and contains information of socket 
	   descriptor for read, message received i.e:timestamp of the server, canonical ip address of source
	   ,port number of source.	   
	 - If the message is not received from the server through the odr within the time out,
	   it sets the route_rediscovery flag=1 and resends the message to the server prompted by user
	    through the odr(on odr_path).
		
 2. SERVER: 
     - Then server binds to the a fixed path name on the unix socket.
	 - Server enters an infinite sequence calls of  msg_receive and msg_send ,awaiting server requests
	   and  responding to client request.
	 - Server waits on recv_from to receive the the client request through the odr (on odr_path).
	 - In  msg_recv function
       Server	 receive's the information sent by the client through the odr (on odr_path).
	   The message_received is in   a single character sequence and contains information of socket descriptor for read, 
	   message sent by the client , canonical ip address of source, port number of source.
     -  Server  then responds to the client request through msg_send function.	   
	 - In msg_send function 
	   client responds to  the client through the odr(on the odr_path.).
	 - The message sent back to the client  is a single character sequence which 
	   contains the following information socket descipter of write,canonical ip address of 
	   server,port number of server and message to be sent. ie.  current time_stamp of the server.
	   
3.  ODR :
    
    - Odr first takes the staleness parameter  through a single command line argument.
    - Odr communicates with server and client through UNIX Sockets and to the other ODR'S using PF_Packet sockets    
    - Odr binds to the unix domain sockets on the odr_path.
	- A routing table is created to store all the routing information.
	- ODR waits on select to get a request from UNIX or  PF_PACKET Socket.
    - When client requests for information from a server UNIX socket is set.
	- Odr checks if  port for recived sun_path from client  is present in  port_sun_path_table.
    - If it is not present it assigns an ephemeral port to recived sun_path from client and stores it in
	  port_sun_path_table  this is done in port_to_path_conv function. 
    - Odr first extracts information from message sent by client this is done in extract_info_from_unix function.
    - First odr check in  routing table entry if route to destination is  present and Staleness is also checked
	  (this  done in check_routing_table_staleness) .
	- staleness is checked (in check_route_staleness function). 
    - If route to destination is present and entry is not stale and  Application payload packet is sent directly to server.
       this is done in gen_update_send_payload.
	- If route to destination is  not present and or is  stale( route_redicovery flag is set to 1).odr message of type 0-RREQ 
	  is brodcasted to all the interfaces (this is done gen_send_rreq function).
    - Get_hw_addrs is used to obtain index  and IP and Ethernet Address.
    -  If odr communicates with a odr 	PF_PACKET Socket is set.
	
	-  If odr message received  is of type 0 - i.e RREQ.
	-  If route_rediscovery bit is not set to 0, it is checked in  routing table entry if route to destination is  present 
	   and Staleness is also checked (this  is done in check_routing_table_staleness). 
    -  If route to destination is present and entry is not stale then odr message of type 1:-RREP is sent back to the
	   source address in the routing table (this is done in gen_update_send_rrep function).
    -  Routing_table is updated along forward route (route to source) (this is done in update_routing_table function).   	   
	-  If 	route to destination is not present or odr is on itermediate node or   route_rediscovery bit is 1.
	   odr message of type 0-RREQ  is flooded or broadcasted to all the interfaces (this is done in flood_rreq function).
	-  is_valid_broadcast function is used to check if a    odr message of type 0-RREQ recived has a different 
	   broadcast id  which is taken into consideration else the RREQ message is ignored.
	-  If odr message of type 0-RREQ reaches destination odr a RREP is sent back to the
	   source address in the routing table (this is done in gen_update_send_rrep function).
	
				
	-  If odr message received  is of type 1 - i.e RREP.
	-  routing_table is updated along reverse route (route to destination) (this done in update_routing_table function).   
    -   If RREP message reaches intermediate node . odr message of type 1- RREP is forwarded along forward path using
	   source address in the routing table (this is done in gen_update_send_rrep function).
	-   If RREP message reaches source odr  node . odr message of type 2- Application payload is along 
	    reverse path (path to destination) using  entries in the routing table (this is done in gen_update_send_payload function).
        Direction is set .i.e is Application payload message is going to the server carrying client message.		
	   
   				
	-  If odr message received  is of type 2 - i.e Application Payload.
	-   Routing_table is updated along forward route (route to source) using update_routing_table function when payload
	    message caries client message. This is FREE RREQ'S.   
    -   If Application Payload message reaches intermediate node and Direction is towards Server . 
	    Application Payload message is forwarded along reverse path(path to server) using  entries in the routing table 
		(this is done in gen_update_send_payload function).
		
	-   If Application Payload message reaches desination odr  node that is of immediate odr connected to server
	    (both on same viruatl machine) . Server is Invoked (this is done in Invoke server function).When Message is received from
		server on unix socket and  message is updated in Application Payload and it is sent to the Client through odr 
		(this is done in gen_update_send_payload function).
		
	-	 If Application Payload message reaches intermediate node and Direction is towards client . 
	     Application Payload message is forwarded along forward path using  entries in the routing table 
	 	 (this is done in gen_update_send_payload function).
		
	-   If Application Payload message reaches desination odr  node that is of immediate odr connected to client
	    (both on same viruatl machine) . Client is Invoked (this is done in Invoke client function).
		1. Message received from server (i.e its timestamp) is sent to client on sun_path the odr 
		   had recived information of request.
        2. sun_path is obtained from the port_sun_path table.

 Test Documentation:
=====================
1)The program is tested and verified for  communication
  from one virtual machine(between 1-10) to another virtual machine( between 1-10).
2)Staleness is also verified by setting a low staleness value.