• Part 1 [60 points total]: Construct a packet filtering tool. You will test your tool by filtering a set of IP datagrams captured during a set of test runs. The captured packets are stored as a sequence of records in a file with the format given below.

  
   0                             15                              31
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          IP Header                           ...
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                            Data                              ...
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ...                                                             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                      IP Header (Packet 2)                    ...
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  ...
  

  The testing of your tool takes the form of the following. When displaying a packet, the format must follow the form below for each IP packet

  IP.port -> IP.port Proto TCPFlags Datalen

  Proto is either "TCP" or "UDP" depending on the protocol field. TCPFlags is a set of characters specifying the TCP flags that are set. These are U, A, P, R, S, or F. And Datalen is the length of the entire IP packet. An example would be:

  157.182.194.39.22 -> 157.182.194.28.7462 TCP S 40

  157.182.194.28.7462 -> 157.182.194.39.22 TCP S,A 40

  . . .

  The first packet would be an TCP packet with IP source address of 157.182.194.39 and source port of 22 going to IP destination address 157.182.194.28 and destination port 7462. The TCP flag that is set is SYN. Packet length is 40 bytes.
  • A [15 points]: Display only IP packets meeting specific IP address criteria. The Source IP address and/or the Destination IP address must match criteria given by the user. This criteria may include a netmask to apply to the IP address as well. This criteria may be given as command line arguments to the filter. With the -s argument specifying the Source IP address to look for and the -d argument specifying the Destination IP address to look for. e.g. $ pfilter -s 157.182.194.28/24 filename might only display information for IP packets that have a source IP address that falls in the 157.182.194.28/24 subnet. Both the Source IP address and Destination IP address may be given or just one of them may be given.
  • B [10 points]: Display only IP packets meeting specific TCP/UDP port criteria. The Source port and/or the Destination port must match criteria given by the user. This criteria may be given as command line arguments to the filter. With the -S argument specifying the Source port number to look for and the -D argument specifying the Destination port number to look for. Both the Source port and Destination port may be given or just one of them may be given.
  • C [10 points]: Display only IP packets meeting specific protocol criteria. The IP Protocol must match criteria given by the user. This criteria may be given as a command line argument to the filter. The choices are "UDP" or "TCP". The argument that may be used is -p.
  • D [10 points]: Display only TCP packets meeting specific flags. The TCP flags must match criteria given by the user. This criteria may be given as a command line argument to the filter. The choices are any TCP flag ("SYN", "FIN", "URG", "RST", "PSH", or "ACK"). The argument that may be used is -f.
  • E [15 points]: At the end of the file, display each individual unique UDP and TCP connection/session. Each session should include the IP addresses, TCP/UDP port numbers, number of bytes sent in each direction, and number of packets sent in each direction.
• Part 2 [20 points total]: Construct a program that takes as it's input: (1) IP address, (2) UDP port number, (3) a variable length string representing a stock symbol, (4) a variable length string representing the type of quote, either "ask" or "bid", (5) the time, in milliseconds, between each retransmission, and (6) the maximum number of times to retransmit before giving up. The routine or object should send quote queries to the IP address and UDP port until it receives a response or retransmits enough times and gives up. The time between each retransmission must be as given by the appropriate parameter. Each query should have a qid (query id) that is echoed by the sender in its response or error message. This qid must be psuedo-random and generated by the client. The format of a quote query and response are given below.

  
  Query:
  
  Bytes:    2     2     Var     1   Var  1
        +------+-----+--------+-+------+-+
        |  0x1 | qid | symbol |0| type |0|
        +------+-----+--------+-+------+-+
  
  Response:
  
  Bytes:    2     2     Var     1   Var  1   Var   1
        +------+-----+--------+-+------+-+-------+-+
        |  0x2 | qid | symbol |0| type |0| price |0|
        +------+-----+--------+-+------+-+-------+-+
  
  Error:
  
  Bytes:    2     2     Var  1      Var        1
        +------+-----+------+-+---------------+-+
        |  0x3 | qid | code |0| error message |0|
        +------+-----+------+-+---------------+-+
  
  

  The routine or object must return whether a response was received or not and the price. The output should be formatted nicely and readable.
• Part 3 [20 points total]: Construct a stock quote server for the client given in Part 1. Construct a program that takes as input a port number to bind to and listen for UDP messages from a stock client. The server should respond to all requests. The server must randomly determine the stock price given some parameters and saved information. They are:
  • There should be a 5% chance that the stock symbol is not defined if the server has not seen the symbol before. If the symbol is not defined, then it will never be defined and all subsequent queries for it will not be defined.
  • For symbols that are defined, but have not been queried before, they have a random value between 5 and 30 dollars. The cent value must also be random with 1/64th resolution. This is the IPO price. The ask and bid prices are the same for an IPO.
  • For symbols that are defined, a stocks ask price may go up (50% chance) or down (50% chance) by up to 10% of the stocks previous value. In other words, the stocks new price will be anywhere between 90% of the previous value and 110% of the previous value.
  • For symbols that are defined, a stocks bid price may go up (50% chance) or down (50% chance) by up to 25% of the stocks previous value. In other words, the stocks new price will be anywhere between 75% of the previous value and 125% of the previous value.
  • Once a query is performed, the stocks price is saved as the last bid price (50% chance) or ask price (50% chance). In other words, the price of the stock is saved as the ask or bid price. The next query will determine new ask and bid prices and one of those two will be saved as the new stock price.

Notes: Your submissions must at least compile before any credit will be given. Submissions that do not compile will not be graded. Submissions submitted after the due date will not be graded. All work must be your own original work. To get partial credit for parts of the assignment, you must demonstrate that those pieces work by themselves. If you share code with others, you will be given a 0 for the assignment. This assignment set is worth 25% of your total grade.