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Programming
Semester 1, 2024
Eike Ritter, David Oswald
The University of Birmingham
30 September, 2024
Exercise 1
Deadline: 14 November, 4pm
The Task
Write a set of programs which maintains the firewall configuation.
1. One program is a server program. Once started, the server should run for ever. It waits for requests, process them and produce a specific response.
The server maintains a collection of firewall rules. For each rule in the
collection of rules, the server also maintains a list of pairs of IP addresses
and ports which have been queried and found to match this rule. The
server also maintains a list of all requests submitted to it. The server
program should accept and process requests and return a response as
follows:
❼ Listing all requests in the order they were given. The command for
this request is R
❼ Adding a rule to the stored rules. This request expects a string which
contains a firewall rule as specified below. If the rule is valid, the
rule is added the set of firewall rules. The response is Rule added
if the rule has been added, and Invalid rule if the string is not a
valid rule. The command for this request is
A
❼ Checking whether a given IP address and port are allowed according
to the rules. If this is the case, the IP address and port are added
to list of matched queries for this rule. If the given address and port
are allowed according to several rules, you should add the IP address
and port to only one rule. If the given IP address and port is checked
again, they may be added to a different rule. If the input does not
provide a valid IP address and a valid port, the response should be
Illegal IP address or port specified. If the IP address and
port are valid and should be accepted according to the rules, the
response should be Connection accepted. If the IP address and
port are valid and should be rejected according to the rules, the
response should be Connection rejected. The command for this
request is
C
1
❼ Delete a valid rule from the stored rules. This should also delete the
list of IP addresses and ports stored for this rule. The rule should
only be deleted if the server stores exactly the same rule. In all
other cases, no action should be taken except returning a suitable
message. If the specification of the rule is invalid, the response should
be Rule invalid. If the rule is successfully deleted, the response
should be Rule deleted. If the rule is valid but not found on the
server, the response should be Rule not found. The command for
this request is
D
❼ Return all rules and for each rule list all IP addresses and ports
which are stored with it. More precisely, for each rule, the response
should be
Rule:
where is the specification of the rule as given below, followed
by
Query:
for each query stored with this firewall rule. The command for this
request is L
❼ For any other request, the response should be Illegal request.
There are two ways of interacting with the server program.
❼ The first one is to start the server with
-i
where is the way to call the server program, typ ically ./server. In this mode the server reads an command from
standard input, prints the response and waits for the next input.
❼ The second way of running the server is
where is the way to call the server program, typ ically ./server, and is the port on which the server listens
for incoming connections. A client program, which you will have to
write as well, makes it possible to send commands to the server pro gram and display the results on standard output. The client should
be called with
without any quotes, e.g.
./client localhost 2200 A 147.188.193.15 22
All other ways of calling the client program should return an error
message.
2
The specification of a firewall rule is below.
A rule is of the form
where is either a single IP address, which has the form xxx.xxx.xxx.xxx,
where xxx is a number between 0 and 255, or-,
where and are IP addresses, and is
smaller than. Assume that IP addresses and ports are separated
by exactly one space character.
Similarly, is either a single port number, which is a number between
0 and 65535, or-, where and are ports and
is smaller than .
Examples of such rules would be
147.188.193.0-147.188.194.255 21-22
147.188.192.41 443
Your server program should maximise the degree of concurrency and not contain
any memory leaks.
Submission and Marking
❼ You should submit the file server.c and client.c on the appropriate
canvas-quiz. The marking scripts will execute the command make with
the Makefile provided in the archive on canvas to produce all required
binaries.
❼ The zip-archive on canvas contains a Makefile and a basic test script is
provided in the file test.sh. The Makefile and the test script will only
work if server.c and client.c are in the same directory as the Makefile
and the test script respectively. The test script tests the cases of adding
a rule both interactively and via sockets. It is run by changing into the
directory containing the binaries and then running
./test.sh
We will use more advanced scripts for marking which test all the specified
functionality, including concurrency and memory leaks. If the basic test
script does not work, all other scripts are likely to fail as well.
❼ Code which does not compile on the virtual machine provided will be
awarded 0 marks.
Hints
❼ You should start by implementing the interactive version of the server
(the version running with server -i) and the R-command. Sockets and
concurrency will be explained in later lectures.
3
❼ You may use the code provided in the lectures in your assignments as you
see fit.
4
Programming
Semester 1, 2024
Eike Ritter, David Oswald
The University of Birmingham
30 September, 2024
Exercise 1
Deadline: 14 November, 4pm
The Task
Write a set of programs which maintains the firewall configuation.
1. One program is a server program. Once started, the server should run for ever. It waits for requests, process them and produce a specific response.
The server maintains a collection of firewall rules. For each rule in the
collection of rules, the server also maintains a list of pairs of IP addresses
and ports which have been queried and found to match this rule. The
server also maintains a list of all requests submitted to it. The server
program should accept and process requests and return a response as
follows:
❼ Listing all requests in the order they were given. The command for
this request is R
❼ Adding a rule to the stored rules. This request expects a string which
contains a firewall rule as specified below. If the rule is valid, the
rule is added the set of firewall rules. The response is Rule added
if the rule has been added, and Invalid rule if the string is not a
valid rule. The command for this request is
A
❼ Checking whether a given IP address and port are allowed according
to the rules. If this is the case, the IP address and port are added
to list of matched queries for this rule. If the given address and port
are allowed according to several rules, you should add the IP address
and port to only one rule. If the given IP address and port is checked
again, they may be added to a different rule. If the input does not
provide a valid IP address and a valid port, the response should be
Illegal IP address or port specified. If the IP address and
port are valid and should be accepted according to the rules, the
response should be Connection accepted. If the IP address and
port are valid and should be rejected according to the rules, the
response should be Connection rejected. The command for this
request is
C
1
❼ Delete a valid rule from the stored rules. This should also delete the
list of IP addresses and ports stored for this rule. The rule should
only be deleted if the server stores exactly the same rule. In all
other cases, no action should be taken except returning a suitable
message. If the specification of the rule is invalid, the response should
be Rule invalid. If the rule is successfully deleted, the response
should be Rule deleted. If the rule is valid but not found on the
server, the response should be Rule not found. The command for
this request is
D
❼ Return all rules and for each rule list all IP addresses and ports
which are stored with it. More precisely, for each rule, the response
should be
Rule:
where
by
Query:
for each query stored with this firewall rule. The command for this
request is L
❼ For any other request, the response should be Illegal request.
There are two ways of interacting with the server program.
❼ The first one is to start the server with
where
standard input, prints the response and waits for the next input.
❼ The second way of running the server is
where
for incoming connections. A client program, which you will have to
write as well, makes it possible to send commands to the server pro gram and display the results on standard output. The client should
be called with
without any quotes, e.g.
./client localhost 2200 A 147.188.193.15 22
All other ways of calling the client program should return an error
message.
2
The specification of a firewall rule is below.
A rule is of the form
where
where xxx is a number between 0 and 255, or
where
smaller than
by exactly one space character.
Similarly,
0 and 65535, or
Examples of such rules would be
147.188.193.0-147.188.194.255 21-22
147.188.192.41 443
Your server program should maximise the degree of concurrency and not contain
any memory leaks.
Submission and Marking
❼ You should submit the file server.c and client.c on the appropriate
canvas-quiz. The marking scripts will execute the command make with
the Makefile provided in the archive on canvas to produce all required
binaries.
❼ The zip-archive on canvas contains a Makefile and a basic test script is
provided in the file test.sh. The Makefile and the test script will only
work if server.c and client.c are in the same directory as the Makefile
and the test script respectively. The test script tests the cases of adding
a rule both interactively and via sockets. It is run by changing into the
directory containing the binaries and then running
./test.sh
We will use more advanced scripts for marking which test all the specified
functionality, including concurrency and memory leaks. If the basic test
script does not work, all other scripts are likely to fail as well.
❼ Code which does not compile on the virtual machine provided will be
awarded 0 marks.
Hints
❼ You should start by implementing the interactive version of the server
(the version running with server -i) and the R-command. Sockets and
concurrency will be explained in later lectures.
3
❼ You may use the code provided in the lectures in your assignments as you
see fit.
4